Herbs & Botanicals · Traditional diarrhoea and blood-sugar leaf

Guava leaf

Q: What is guava leaf?

It is the leaf of the guava tree (Psidium guajava), used as a tea, a simmered drink or an extract for diarrhoea and, more recently, blood sugar.

Q: Does guava leaf stop diarrhoea?

One open-label trial in 109 adults found recovery in about 3 days versus about 5 days with oral rehydration alone, and a capsule trial found less belly pain but no change in stools. The evidence is small. Oral rehydration comes first.

Q: Is it safe for children with diarrhoea?

That is not known. A 2024 review says safety in children is an open question, and the one infant trial was small and old. Use oral rehydration solution and see a doctor, because children can dehydrate fast.

Q: Does guava leaf lower blood sugar?

Small trials of a Japanese guava leaf tea lowered the blood sugar rise after a meal, less than the drug voglibose. Long-term benefit has not been shown, and the main review is by the tea maker.

Q: Can it cause low blood sugar with diabetes drugs?

No low blood sugar was reported in the tea maker's review of people on usual treatment, but studies were small. A stronger combined effect cannot be ruled out, so ask your doctor or pharmacist first.

Q: Should I stop it before surgery?

Tell your surgical team. Because it may lower blood sugar, some teams ask people to pause herbs that affect blood sugar. We found no guava-specific surgical guidance; this is a general precaution.

Q: Is it safe in pregnancy or breastfeeding?

No safety data exist. A leaf extract relaxed rat uterus tissue in the lab. Avoid medicinal amounts and ask your doctor or midwife.

Q: Can the tannins cause constipation or affect iron?

Ordinary tea reduced iron absorption in volunteers, and tannin-rich leaf teas could in theory be constipating. No study of guava leaf tea has tested either, so ask a pharmacist if you have iron deficiency.

Q: Does it interact with other medicines?

Test-tube tests suggest only weak effects on liver enzymes that process many drugs, but no human interaction study exists. People on warfarin or other narrow-margin drugs should ask a pharmacist.

Psidium guajava · also called Guava leaves, guava leaf tea

Guava leaf comes from the guava tree, the same tree that gives the fruit. The leaves are made into a tea or a simmered drink and used in many countries for diarrhoea and, more recently, for blood sugar. A few small human trials suggest it may shorten short bouts of diarrhoea and soften the blood-sugar rise after a meal, but the research is limited and some of it comes from a tea maker. Do not use it instead of rehydration for diarrhoea or instead of diabetes treatment, and ask a doctor or pharmacist first if you take blood-sugar medicines or are treating a child.

General information, not medical advice. Last substantive update October 25, 2026 · Not medically reviewed. A named clinician has not signed off on this page. How this page is made

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About Guava leaf

Guava leaf is a traditional remedy for diarrhoea that has also been tried for blood sugar. Human evidence is small and mostly short-term. It looks well tolerated in short trials, but it may add to the effect of diabetes medicines, and it is not a replacement for rehydration, especially in children.

Safety first

Diabetes medicines: guava leaf tea lowers the rise in blood sugar after a meal. The tea maker's review reports no low blood sugar when it was used with usual treatment, but those studies were small. If you take insulin or diabetes tablets, ask your doctor or pharmacist before using it, and do not change prescribed treatment. Tell your surgical team before planned surgery.

Diarrhoea: oral rehydration comes first. Babies, children, older people and pregnant women can dehydrate quickly. Bloody diarrhoea, high fever, severe pain, signs of dehydration or diarrhoea lasting more than a few days need a doctor. Safety in children is an open question in the 2024 review.

Tannins: guava leaf is rich in tannins. Ordinary tea, which is also rich in tannins, reduced iron absorption in volunteers. We found no iron or constipation study of guava leaf itself, so this is a reasoned caution.

Pregnancy and breastfeeding: no safety data. A leaf extract relaxed rat uterus tissue in the lab. Avoid medicinal amounts and ask your doctor or midwife.

Other points: one case report links guava tea to an allergic skin reaction (only the title was available). Liver and kidney tests stayed normal in the trials, and no human liver injury report was found. Test-tube tests suggest weak effects on drug-processing enzymes, but no human study has checked this. No regulator monograph was found. Ask a doctor or pharmacist about amounts and your medicines.

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What it is

Psidium guajava is a tropical tree grown for its fruit. The leaf is used as a decoction or tea and as extracts. Compounds studied include quercetin and its sugar-linked forms, guaijaverin, avicularin, ellagic acid and tannins.

The fruit is a different story. A trial of ripe fruit in healthy students found different effects from the leaf tea studies, so the two should not be mixed up. See the guava fruit page for the fruit.

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What the research shows

Diarrhoea: a 2024 systematic review found only three clinical trials among 23 articles; most were lab or animal studies. In the best-known trial, 109 adults took a leaf decoction or oral rehydration solution; recovery took about 72 hours versus 120 hours. It was open label and registered late. A second trial of a standardised capsule found less belly pain but no change in stools. A small 2000 trial in babies compared guava with another herbal decoction.

Blood sugar: small trials, mostly of one Japanese tea, reported a lower rise after a meal, milder than the drug voglibose, and small changes over 12 weeks with no control group. The review describing them is by the tea maker, and one author holds patents on the tea.

Other uses: one pilot found less knee pain; period pain and many other uses rest on lab studies only.

We found no EMA, NCCIH, LiverTox or LactMed entry for guava leaf (not verified where pages could not be opened).

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History and tradition

A 2024 review found guava used for diarrhoea in 44 countries, most often as a leaf decoction. The leaf has also been a folk remedy for diabetes in East Asia, and a commercial guava leaf tea has been sold in Japan as a Food for Specified Health Uses (as described by its maker; not verified here).

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At a glance

Traditional uses history, not proof

Diarrhoea and dysentery (leaf decoction)
Diabetes (folk remedy in East Asia)
Period pain (some African communities)

Studied for research

Short bouts of diarrhoea in adults: low
Blood sugar after a meal: low
Longer-term blood sugar and insulin: insufficient
Cholesterol and triglycerides: insufficient
Knee pain: very low (one pilot)
Babies' rotavirus diarrhoea: very low

Main compounds

Quercetin and its sugar forms (flavonoids)
Guaijaverin
Avicularin
Ellagic acid
Tannins (guavins)

Common forms

Leaf decoction
Leaf tea
Standardised extract
Capsule

Research links: PubMed: guava leaf decoction trial in acute diarrhoea (Birdi 2020) · PubMed: systematic review of guava extract in acute diarrhoea (2024) · PubMed: guava and diarrhoea, ethnobotany and safety review (2024) · PubMed: guava leaf extract and blood sugar (Deguchi 2010) · Research Library · Genes & Biomarkers Library

The plant and its history

Accepted scientific name: Psidium guajava
Naming authority: L.
Common names: Guava leaf (en); Guava leaves (en); Guava (en)
Botanical family: Myrtaceae (myrtle family)
Classification: Plantae > Myrtales > Myrtaceae > Psidium > Psidium guajava
Native range: A tropical tree widely grown in tropical and subtropical countries (Gutierrez 2008). Exact native range not stated in the sources read.
Habitat: Tropical and subtropical regions; not verified in detail.
What the plant looks like: Plant: A tropical tree. The leaf is the medicinal part discussed here; the fruit is eaten as food. Detailed leaf description not taken from the sources read.
Cultivation: Widely cultivated for fruit. Not verified for leaf production.
Harvest and processing: Leaves are used fresh or dried as a decoction or tea, as aqueous or alcohol extracts, or as standardised capsules (e.g. QG-5, standardised to quercetin).
Look-alikes and adulterants: Name: Guava fruit (Psidium guajava); Note: The same tree, a different plant part. A 6-week trial of ripe fruit in healthy students found different effects from leaf tea studies. Leaf results do not apply to the fruit and the reverse.; Name: Other Myrtaceae leaves (for example jamun, Syzygium cumini); Note: Studied for blood sugar too, but they are different plants; results do not transfer.; Name: Strawberry guava (Psidium cattleyanum); Note: A related species; not tested in the sources read. Check that a product names Psidium guajava.
Sustainability and conservation: Not assessed here.

Traditional use and history history, not clinical proof

Tradition or era	Documented use	Source
Traditional medicine in 44 countries (per a 2024 review)	Guava, mostly the leaf as a decoction taken by mouth, is used for diarrhoea and dysentery.	p39246650
East Asia and other regions	The leaf has been used as a folk remedy for diabetes. In Japan a commercial guava leaf tea was approved as a Food for Specified Health Uses (per the maker's review).	p20181067
Rural African communities	Guava leaf used for period pain.	p19377271

Traditional use shows how a plant was used. It does not show that a supplement works or is safe today.

What is inside, and how it may work

What the plant contains and how those compounds act in cells and animals. Laboratory and animal mechanisms are not proven effects in people.

Main compounds

Compound	Family	Where it is concentrated	Activity studied	Level of evidence
Quercetin PubChem 5280343	flavonol (flavonoid)	leaf A leaf capsule was standardised to about 1 mg quercetin-equivalent per 500 mg (per the Liu review).	Suspected active antidiarrhoeal compound together with its sugar forms; blocks CYP enzymes more strongly than the whole leaf extract in the lab. ^{12 13 3 18}	Laboratory research
Guaijaverin PubChem 5481224	flavonol glycoside	leaf	Isolated from guava leaf; listed among the antidiarrhoeal or antibacterial compounds in the 2024 review. ^{12 18}	Laboratory research
Avicularin PubChem 5490064	flavonol glycoside	leaf	Listed among compounds present in guava in the 2024 review. ^{12 18}	Laboratory research
Ellagic acid PubChem 5281855	polyphenol	leaf	Listed among compounds in the 2024 review. ^{12 18}	Laboratory research
Guavin B (an ellagitannin) PubChem 78172774	tannin	leaf	Tannins from guava (guavins A to D) are named in the reference list of the tea-maker's review; their role in glucose or gut effects was not read. ^{3 18}	Laboratory research

Mechanisms, receptors and pathways

Target or pathway	Gene or receptor	What was found	Level
Carbohydrate-digesting enzymes (alpha-glucosidase, maltase, sucrase, amylase)	Alpha-glucosidase	Guava leaf extract blocked these enzymes in the test tube, as the drugs acarbose and voglibose do; this would slow sugar release in the gut. IC50 2.25 mg/mL for guava versus 6.41 mg/mL for acarbose in one assay. ^{3 8}	Laboratory research
Gut muscle activity and bacteria	Not specified	Leaf extracts reduced contractions of isolated guinea pig and rabbit intestine and were antibacterial against Shigella and cholera bacteria in the test tube. ^{12 6}	Laboratory research
Uterine smooth muscle	Not specified	Leaf extract relaxed isolated rat uterus and blocked oxytocin-induced contractions. ²	Animal research
Drug-metabolising liver enzymes (CYP2C8, CYP2C9, CYP3A4)	CYP450	Extract blocked these enzymes weakly compared with quercetin and grapefruit juice in vitro; no enzyme induction in rat liver after one month. Reported by the tea maker. ³	Laboratory research

Absorption, metabolism and elimination

Absorption: Not found for any guava leaf compound in people in the sources read.
Distribution: Not found.
Metabolism: Not found for guava leaf compounds in people.
Elimination: Not found.
Bioavailability: Not found. Quercetin is described as a main suspect compound but its fate after drinking guava leaf was not studied in the sources read.

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Isolated compounds versus whole extracts

The diarrhoea and blood-sugar studies used whole-leaf preparations (a decoction, a commercial tea made from an aqueous extract, and a quercetin-standardised capsule). It is not known whether quercetin alone or its sugar forms can explain the effects; the 2024 review explicitly asks this. Isolated compounds should not be assumed to behave like the leaf.

Nutritional composition

Guava leaf tea is a drink, not a source of nutrients. The fruit is a food rich in fibre and vitamin C; its studies are a different topic and are covered on the guava fruit page.

10benefits and uses looked at

19studies and sources checked

Low certaintybest evidence rating found

7lab markers tracked in trials

3 low certainty2 very low certainty5 not enough evidence

What was looked at

The 10 benefits and uses checked for Guava leaf, each with how strong the evidence is. Tap one to open it.

Short bouts of infectious diarrhoea in adults (leaf decoction)Low certainty
Belly pain with diarrhoea (standardised leaf capsule)Low certainty
Diarrhoea from rotavirus in babies and young childrenVery low certainty
Blood sugar after a meal (leaf tea, single serving)Low certainty
Longer-term blood sugar and insulin (HbA1c, fasting glucose, insulin)Not enough evidence
Cholesterol and triglycerides (leaf tea)Not enough evidence
Antibacterial and gut-calming effects in the lab (animal and test-tube only)Not enough evidence
Knee pain (leaf extract, 12 weeks)Very low certainty
Period pain (traditional use; rat-tissue work only)Not enough evidence
Cough, allergy, pain, antioxidant and other lab findingsNot enough evidence

Lab markers tracked in the studies

Time to return to normal stoolsAbdominal pain during diarrhoeaBlood glucose 2 hours after a mealFasting glucose and HbA1cInsulin, C-peptide and HOMA-IRTotal cholesterol and triglyceridesKnee pain and stiffness scores (JKOM, visual analogue scale)

What is Guava leaf good for?

The main studied uses and how strong the human evidence is for each. 'Low' means a few small studies; 'insufficient' means too little evidence; lab-only items are marked as such.

Short bouts of infectious diarrhoea in adults (leaf decoction)Low certaintyIn one open-label trial in 109 adults, a guava leaf decoction ended acute diarrhoea in about 3 days versus about 5 days with oral rehydration solution alone. One small trial, no placebo, registered late. Rehydration still comes first. Belly pain with diarrhoea (standardised leaf capsule)Low certaintyA placebo-controlled trial of a standardised leaf capsule found a shorter time with belly pain, but no change in how many loose stools people had. Diarrhoea from rotavirus in babies and young childrenVery low certaintyA small 2000 trial in 62 babies compared guava with another herbal decoction, not with rehydration or placebo. Not enough to guide care for children. Blood sugar after a meal (leaf tea, single serving)Low certaintySmall trials of guava leaf tea reported a lower blood sugar rise after a meal, milder than the drug voglibose. The review describing them is by the tea maker. Longer-term blood sugar and insulin (HbA1c, fasting glucose, insulin)Not enough evidenceA 12-week study in 15 men with no control group showed small changes in fasting glucose that were not significant. Not a substitute for diabetes care. Cholesterol and triglycerides (leaf tea)Not enough evidenceCholesterol and triglycerides fell only in tiny subgroups with high starting levels in the same uncontrolled study. Antibacterial and gut-calming effects in the lab (animal and test-tube only)Not enough evidenceTest-tube and animal studies show antibacterial and gut-calming effects. They explain the traditional use but do not prove it works in people. Knee pain (leaf extract, 12 weeks)Very low certaintyOne small double-blind pilot in Japan found less knee pain after 12 weeks of a leaf extract than with placebo. Key numbers were not in the abstract. Period pain (traditional use; rat-tissue work only)Not enough evidenceUsed traditionally in some African communities. A leaf extract relaxed rat uterus tissue in the lab; no study in women. Cough, allergy, pain, antioxidant and other lab findingsNot enough evidenceAntioxidant, anti-allergy, anti-cough and other effects are reported in lab and animal studies only.

Benefits, one by one

Each card is a research question, not a promise. Tap a goal to filter. Open a card to see the studies, doses and limits.

Short bouts of infectious diarrhoea in adults (leaf decoction)

Low certainty

In one open-label trial in 109 adults, a guava leaf decoction ended acute diarrhoea in about 3 days versus about 5 days with oral rehydration solution alone. It is one small trial that was not blinded and was registered late, so it is a promising signal rather than proof.

3 studiesLeaf decoction in the Birdi trial (14 leaves was about 7.4 g per serv…

Studies, doses and limits

What the trials found

Birdi 2020: 109 adults with acute infectious diarrhoea, open label, decoctions of 6, 10 or 14 leaves versus oral rehydration solution; the 14-leaf decoction worked best (about 72 versus 120 hours to normal) with no adverse events reported and normal blood, liver and kidney tests. Garrido 2024 found only three clinical trials among 23 articles in its systematic review; Liu 2024 describes two adult trials.

Results

Faster recovery with the strongest leaf decoction in one open-label trial; the rest of the evidence is lab and animal work.

Effect sizes as reported

About 72 hours versus 120 hours to normal stools (Birdi 2020). No confidence interval in the abstract.

Why this rating

One small open-label randomised trial, registered after it began, with no placebo. A second adult trial (Lozoya) did not change stool frequency or consistency. Systematic reviews call the human evidence limited.

Form and dose studied

Leaf decoction in the Birdi trial (14 leaves was about 7.4 g per serving, three times a day for the trial period). Trial detail, not advice. Tea, capsules and extracts are not interchangeable with this decoction.

Who was studied

Adults aged 18 to 60 with uncomplicated acute diarrhoea of unknown cause.

Limits

Open label, no placebo, retrospective registration, adults only, uncomplicated cases only, short follow-up.

Why researchers looked

Guava leaf is used for diarrhoea and dysentery in 44 countries, and lab work shows antibacterial and gut-calming effects.

Traditional use

A leaf decoction is the most common traditional preparation for diarrhoea (Liu 2024). Traditional use is not proof of benefit.

Proposed mechanism Laboratory research

Lab and animal work reports antibacterial, anti-motility, anti-secretory and anti-inflammatory effects of guava leaf extracts. Quercetin and its sugar-linked forms are suspected active compounds, but the 2024 review says this is not settled. Whether this explains the human result is unknown.

A proposed mechanism does not show that the effect happens in people.

Diarrhoea can cause dangerous dehydration, especially in babies, children, older people and pregnant women. Oral rehydration comes first. Bloody diarrhoea, high fever, severe pain, or diarrhoea lasting more than a few days needs a doctor.

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Belly pain with diarrhoea (standardised leaf capsule)

Low certainty

In a placebo-controlled trial, a guava leaf capsule shortened the time adults had belly pain during acute diarrhoea, but did not change how many loose stools they had or how loose they were.

2 studiesA standardised capsule (500 mg, every 8 hours for 3 days in the trial…

Studies, doses and limits

What the trials found

Lozoya 2002: a standardised leaf capsule (QG-5) versus placebo for 3 days in adults with acute diarrhoea; the abstract reports a shorter duration of abdominal pain. The 2024 Liu review states stool frequency and consistency did not change.

Results

Mixed: less belly pain, no change in stools.

Effect sizes as reported

No numbers in the abstract.

Why this rating

One double-blind trial, small, with a single positive outcome and other outcomes unchanged; read from abstract plus a review.

Form and dose studied

A standardised capsule (500 mg, every 8 hours for 3 days in the trial). Trial detail, not advice.

Who was studied

Adults with acute diarrhoea in Mexico.

Limits

One trial; abstract only; funding not stated; pain was one of several outcomes.

Why researchers looked

Guava leaf has antispasmodic (muscle-relaxing) activity in the gut in lab tests.

Traditional use

Leaf preparations are used traditionally for stomach cramps with diarrhoea.

Proposed mechanism Laboratory research

Guava leaf extracts reduced contractions of isolated guinea pig and rabbit intestine in lab studies (reported in the 2024 review). The capsule was standardised to quercetin content.

A proposed mechanism does not show that the effect happens in people.

Pain with diarrhoea can also signal infection or another cause that needs a doctor.

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Diarrhoea from rotavirus in babies and young children

Very low certainty

A 62-patient Chinese trial reported faster recovery with a guava preparation than with a herbal comparison decoction. The trial is old and small, the preparation is not described, and it did not test against oral rehydration or placebo. This is not enough to guide care for children.

2 studiesNot described in the abstract. No amounts given.

Studies, doses and limits

What the trials found

Wei 2000: 62 infants with rotavirus enteritis; recovery in 3 days was 87.1% with guava versus 58.1% with Gegen Qinlian decoction; diarrhoea stopped in 25.1 versus 38.7 hours.

Results

Positive against a herbal comparison in one small trial.

Effect sizes as reported

87.1% versus 58.1% recovered in 3 days; 25.1 versus 38.7 hours.

Why this rating

A single small trial from 2000 with an unclear preparation and an active herbal comparator, read only from its abstract.

Form and dose studied

Not described in the abstract. No amounts given.

Who was studied

Infants and young children with rotavirus diarrhoea (ages not stated in the abstract).

Limits

Old, small, abstract only, no placebo or rehydration-only arm, unclear methods.

Why researchers looked

Rotavirus is a leading cause of diarrhoea in young children, and guava leaf extract blocked rotavirus growth in test-tube studies (reported in the 2024 review).

Traditional use

Guava preparations are used for children's diarrhoea in some traditions; the 2024 review asks whether guava leaf is safe in children at all.

Proposed mechanism Laboratory research

An aqueous leaf extract inhibited two rotavirus strains in cell-culture tests (Liu 2024, citing Goncalves 2005). Cell-culture results do not show the same effect in a child.

A proposed mechanism does not show that the effect happens in people.

Do not treat a baby or child with diarrhoea at home with leaf teas instead of rehydration solution and medical advice. Dehydration can become dangerous quickly in small children.

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Blood sugar after a meal (leaf tea, single serving)

Low certainty

In small short trials, guava leaf tea lowered the blood sugar rise after a meal, but less than the diabetes drug voglibose. The main reviewer works for the company that makes the tea.

2 studiesGuava Leaf Tea made from an aqueous leaf extract (a Japanese commerci…

Studies, doses and limits

What the trials found

Deguchi 2010 (review) describes a crossover trial of 20 hospitalised people with type 2 diabetes: after a single serving the glucose 2 hours after a meal fell from about 160 to 143 mg/dL with Guava Leaf Tea and to 133 mg/dL with voglibose. The tea effect was milder (p<0.01). No hypoglycaemia was noted. The review is by authors from the tea maker and one holds patents on the tea.

Results

Short-term lowering of the after-meal rise in small trials, milder than a drug.

Effect sizes as reported

About 17 mg/dL lower 2-hour glucose with tea in the crossover trial (about 160 to 143 mg/dL), versus about 27 mg/dL with voglibose, as reported secondhand.

Why this rating

Small trials, mostly single-dose, described secondhand in a review by the product maker; no independent pooled analysis of guava leaf alone was found.

Form and dose studied

Guava Leaf Tea made from an aqueous leaf extract (a Japanese commercial tea). Other teas, capsules or homemade infusions may differ in strength. No amounts given.

Who was studied

People with type 2 diabetes in hospital; some trials in people with pre-diabetes.

Limits

Industry-linked review; trial details not read directly; short effect; only after-meal glucose.

Why researchers looked

Guava leaf has been a folk remedy for diabetes in East Asia, and lab tests show it blocks starch-digesting enzymes (alpha-glucosidase), as the drugs acarbose and voglibose do.

Traditional use

Folk remedy for diabetes in East Asia and other regions (Deguchi 2010).

Proposed mechanism Laboratory research

Guava leaf extract blocked alpha-glucosidase enzymes in the test tube (Deguchi 2010; Hsu 2024 found IC50 2.25 mg/mL for guava versus 6.41 mg/mL for acarbose in the same assay). This slows sugar release in the gut. Test-tube strength does not equal effect in people.

A proposed mechanism does not show that the effect happens in people.

If you take diabetes medicines, adding another blood-sugar-lowering product can matter. Talk to your doctor or pharmacist first and do not change prescribed treatment.

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Longer-term blood sugar and insulin (HbA1c, fasting glucose, insulin)

Not enough evidence

A 12-week study in 15 men with pre-diabetes or mild type 2 diabetes showed small, mostly non-significant changes in fasting glucose, with HbA1c lower in some pre-diabetic men and lower insulin levels. It had no control group, so we cannot say the tea caused the changes.

2 studiesGuava Leaf Tea with meals in the study. No amounts given.

Studies, doses and limits

What the trials found

Deguchi 2010 reports a 12-week study of 15 men: fasting glucose 136 to 131 mg/dL (p=0.07); 5 of 7 pre-diabetic men had a lower HbA1c; insulin, C-peptide and HOMA-IR fell significantly. Other long-term trials are mentioned in the review but their details were not extracted here.

Results

Small changes; the main glucose result did not reach statistical significance.

Effect sizes as reported

Fasting glucose about 5 mg/dL lower (p=0.07). Insulin measures significantly lower.

Why this rating

Tiny, uncontrolled studies reported through a review by the product maker. We found no independent controlled long-term trial.

Form and dose studied

Guava Leaf Tea with meals in the study. No amounts given.

Who was studied

Men with pre-diabetes or mild type 2 diabetes (15 people).

Limits

No control group, very small, subgroup claims, industry-linked authors, short term.

Why researchers looked

If after-meal spikes are reduced, long-term control might improve.

Traditional use

Leaf tea is used in several countries as a daily drink for diabetes.

Proposed mechanism Animal research

Slowing carbohydrate digestion and, in mouse studies, effects on insulin resistance and liver sugar handling. Mouse results are not shown in people.

A proposed mechanism does not show that the effect happens in people.

Do not replace prescribed diabetes care. Lower insulin levels can also be a sign of changed treatment or diet.

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Cholesterol and triglycerides (leaf tea)

Not enough evidence

In the same small 12-week study, total cholesterol and triglycerides fell only in the few men whose levels were high at the start. That is too little to say the tea lowers blood fats.

1 studiesGuava Leaf Tea. No amounts given.

Studies, doses and limits

What the trials found

Deguchi 2010: after 12 weeks of Guava Leaf Tea, total cholesterol and triglycerides fell significantly in subgroups with high starting values (7 and 5 men).

Results

Subgroup changes only.

Effect sizes as reported

Not given in a form we could check.

Why this rating

Subgroups of 5 and 7 people, no control group, industry-linked review.

Form and dose studied

Guava Leaf Tea. No amounts given.

Who was studied

Men with high starting cholesterol or triglycerides (very small subgroups).

Limits

Subgroup findings can arise by chance and by regression to the mean.

Why researchers looked

Blood-sugar spikes and blood fats are linked, so reducing one might help the other.

Traditional use

Not a prominent traditional use in the sources read.

Proposed mechanism Pharmacological theory

Proposed to follow from lower after-meal sugar. Not tested directly.

A proposed mechanism does not show that the effect happens in people.

If you take cholesterol medicines, do not stop them. The review reports no hypoglycaemia or odd results when the tea was taken with such medicines.

Antibacterial and gut-calming effects in the lab (animal and test-tube only)

Not enough evidence

Many lab and animal studies report that guava leaf extracts kill or slow some bacteria that cause diarrhoea and calm gut muscles. These findings explain why people tried it, but they do not show it works in people.

3 studiesNot applicable.

Studies, doses and limits

Results

Lab and animal findings only.

Why this rating

Lab and animal studies only; clinical meaning not defined (Garrido 2024).

Who was studied

Cells, bacteria, rodents, isolated tissue.

Limits

Not human. Results depend on extract and concentration.

Why researchers looked

To find out why the leaf is used for diarrhoea.

Traditional use

Backs up traditional leaf use for diarrhoea and dysentery.

Proposed mechanism Laboratory research

A leaf decoction was antibacterial against Shigella flexneri (EC50 0.3 mg/mL) and Vibrio cholerae (0.8 mg/mL) in the test tube; extracts calmed isolated animal intestine; an aqueous leaf extract slowed two rotavirus strains in cell culture (Liu 2024). Many studies used concentrations far above what the body would see.

A proposed mechanism does not show that the effect happens in people.

A lab antibacterial effect does not make leaf tea a safe replacement for treatment of serious infection.

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Knee pain (leaf extract, 12 weeks)

Very low certainty

A pilot double-blind trial in Japan found less knee pain and stiffness after 12 weeks of a guava leaf extract than with placebo. It is a single small pilot, and key details such as group sizes were not in the abstract.

1 studiesA guava leaf extract, 1 g a day in the trial. Trial detail, not advic…

Studies, doses and limits

What the trials found

Kakuo 2018: randomised, double-blind, placebo-controlled pilot; guava leaf extract or placebo daily for 12 weeks. At week 12 pain and stiffness (a JKOM subscore) and VAS knee pain were lower with guava.

Results

Positive in one pilot trial.

Effect sizes as reported

Not given in the abstract.

Why this rating

A single pilot trial read only from its abstract, with no numbers.

Form and dose studied

A guava leaf extract, 1 g a day in the trial. Trial detail, not advice.

Who was studied

Japanese adults with knee pain and no previous treatment.

Limits

Pilot; number of participants and funding not in the abstract; short follow-up; subjective pain outcome.

Why researchers looked

A rat study suggested guava leaf extract slowed osteoarthritis changes, so researchers tested it in people with knee pain.

Traditional use

Not a traditional use in the sources we read.

Proposed mechanism Animal research

Based on a rat osteoarthritis model cited by the trial authors. How it might work in people was not tested.

A proposed mechanism does not show that the effect happens in people.

Knee pain that is severe, sudden, with swelling or fever, or after injury needs a doctor.

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Period pain (traditional use; rat-tissue work only)

Not enough evidence

In some African communities guava leaf is used for period pain. In the lab, a leaf extract relaxed rat uterus muscle. No study in women was found.

1 studiesNot applicable.

Studies, doses and limits

Results

Lab only.

Why this rating

Rat tissue only.

Who was studied

Isolated rat uterine tissue.

Limits

Not human. The same relaxing effect on the uterus is a reason for caution in pregnancy.

Why researchers looked

To test the traditional claim that guava leaf eases cramping of the womb.

Traditional use

Used for primary dysmenorrhoea in some rural African communities (Chiwororo 2009).

Proposed mechanism Laboratory research

An aqueous leaf extract reduced spontaneous contractions of isolated rat uterus and blocked contractions caused by oxytocin and other triggers. It was tested in tissue, not in animals or women.

A proposed mechanism does not show that the effect happens in people.

Severe period pain, heavy bleeding or pain that is new needs a medical check. Avoid medicinal amounts in pregnancy.

Cough, allergy, pain, antioxidant and other lab findings

Not enough evidence

Reviews list many lab and animal effects of guava leaf, such as antioxidant, anti-allergy, anti-cough and anti-inflammatory activity. None is backed by human trials in the sources we read.

3 studiesNot applicable.

Studies, doses and limits

Results

Lab and animal only.

Why this rating

No human studies read.

Who was studied

Cells and animals.

Limits

Reviews are mostly lab; claims of 'substitutes for drugs' (Kaur 2025) go beyond the evidence.

Why researchers looked

Guava is a widely used folk plant, so researchers screen it for many actions.

Traditional use

Used widely in folk medicine around the world (Gutierrez 2008).

Proposed mechanism Laboratory research

Various lab and animal models. A mouse study found no toxicity at the doses tested (Dibaba 2026), which says little about benefit.

A proposed mechanism does not show that the effect happens in people.

Do not replace treatment for asthma, allergy or infection with leaf tea.

^{7 10 4}

Connections to the rest of health

How Guava leaf connects to the rest of our health knowledge graph. Every link says what kind of connection it is. A safety link (for example to the liver) is a warning, not a benefit. A study that merely mentions a topic never creates a benefit link.

Explore every connection: goals, body systems, organs, symptoms, genes

Kind of connection Connected to Search

A. Wellness goals

Connected to	Kind of connection	Evidence status	Context	Studies
Digestive Support	Potential benefit	Low certainty	Short bouts of infectious diarrhoea in adults (leaf decoction): In one open-label trial in 109 adults, a guava leaf decoction ended acute diarrhoea in about 3 days versus about 5 days with oral rehydration solution alone. It is one small trial that was not blinded and was registered late, so it is a promising signal rather than proof. Belly pain with diarrhoea (standardised leaf capsule): In a placebo-controlled trial, a guava leaf capsule shortened the time adults had belly pain during acute diarrhoea, but did not change how many loose stools they had or how loose they were.	^{1 6 12 13}
Gut Health	Potential benefit	Low certainty	Short bouts of infectious diarrhoea in adults (leaf decoction): In one open-label trial in 109 adults, a guava leaf decoction ended acute diarrhoea in about 3 days versus about 5 days with oral rehydration solution alone. It is one small trial that was not blinded and was registered late, so it is a promising signal rather than proof.	^{1 6 12}
Digestive Support		Very low certainty	Diarrhoea from rotavirus in babies and young children: A 62-patient Chinese trial reported faster recovery with a guava preparation than with a herbal comparison decoction. The trial is old and small, the preparation is not described, and it did not test against oral rehydration or placebo. This is not enough to guide care for children.	^{15 12}
Blood Sugar Balance	Potential benefit	Low certainty	Blood sugar after a meal (leaf tea, single serving): In small short trials, guava leaf tea lowered the blood sugar rise after a meal, but less than the diabetes drug voglibose. The main reviewer works for the company that makes the tea.	^{3 8}
Metabolic Health	Potential benefit	Low certainty	Blood sugar after a meal (leaf tea, single serving): In small short trials, guava leaf tea lowered the blood sugar rise after a meal, but less than the diabetes drug voglibose. The main reviewer works for the company that makes the tea.	^{3 8}
Blood Sugar Balance		Not enough evidence	Longer-term blood sugar and insulin (HbA1c, fasting glucose, insulin): A 12-week study in 15 men with pre-diabetes or mild type 2 diabetes showed small, mostly non-significant changes in fasting glucose, with HbA1c lower in some pre-diabetic men and lower insulin levels. It had no control group, so we cannot say the tea caused the changes.	^{3 10}
Cholesterol Balance		Not enough evidence	Cholesterol and triglycerides (leaf tea): In the same small 12-week study, total cholesterol and triglycerides fell only in the few men whose levels were high at the start. That is too little to say the tea lowers blood fats.	³
Heart Health		Not enough evidence	Cholesterol and triglycerides (leaf tea): In the same small 12-week study, total cholesterol and triglycerides fell only in the few men whose levels were high at the start. That is too little to say the tea lowers blood fats.	³
Digestive Support		Not enough evidence	Antibacterial and gut-calming effects in the lab (animal and test-tube only): Many lab and animal studies report that guava leaf extracts kill or slow some bacteria that cause diarrhoea and calm gut muscles. These findings explain why people tried it, but they do not show it works in people.	^{6 12 7}
Joint Support		Very low certainty	Knee pain (leaf extract, 12 weeks): A pilot double-blind trial in Japan found less knee pain and stiffness after 12 weeks of a guava leaf extract than with placebo. It is a single small pilot, and key details such as group sizes were not in the abstract.	⁹
Mobility Support		Very low certainty	Knee pain (leaf extract, 12 weeks): A pilot double-blind trial in Japan found less knee pain and stiffness after 12 weeks of a guava leaf extract than with placebo. It is a single small pilot, and key details such as group sizes were not in the abstract.	⁹
Womens Wellness		Not enough evidence	Period pain (traditional use; rat-tissue work only): In some African communities guava leaf is used for period pain. In the lab, a leaf extract relaxed rat uterus muscle. No study in women was found.	²
Inflammation Balance		Not enough evidence	Cough, allergy, pain, antioxidant and other lab findings: Reviews list many lab and animal effects of guava leaf, such as antioxidant, anti-allergy, anti-cough and anti-inflammatory activity. None is backed by human trials in the sources we read.	^{7 10 4}

B. Body systems

Connected to	Kind of connection	Evidence status	Context	Studies
Digestive system	Potential benefit	Low certainty	Acute diarrhoea and belly pain in small adult trials. Preparation or compound: Guava leaf decoction; standardised leaf capsule	^{1 13}
Blood sugar	Potential benefit	Low certainty	Lower after-meal glucose in small, industry-linked trials; also a theoretical added effect with diabetes medicines. Preparation or compound: Guava leaf tea	³
Digestive System	Biological association	Low certainty	Studied for: Short bouts of infectious diarrhoea in adults (leaf decoction) Studied for: Belly pain with diarrhoea (standardised leaf capsule)	^{1 6 12 13 15 7}
Immune System	Biological association	Very low certainty	Studied for: Diarrhoea from rotavirus in babies and young children Studied for: Cough, allergy, pain, antioxidant and other lab findings	^{15 12 7 10 4}
Blood Sugar Support	Biological association	Low certainty	Studied for: Blood sugar after a meal (leaf tea, single serving) Studied for: Longer-term blood sugar and insulin (HbA1c, fasting glucose, insulin)	^{3 8 10}
Endocrine System	Biological association	Low certainty	Studied for: Blood sugar after a meal (leaf tea, single serving)	^{3 8}
Cardiovascular System	Biological association	Not enough evidence	Studied for: Cholesterol and triglycerides (leaf tea)	³
Musculoskeletal System	Biological association	Very low certainty	Studied for: Knee pain (leaf extract, 12 weeks)	⁹
Reproductive System	Biological association	Not enough evidence	Studied for: Period pain (traditional use; rat-tissue work only)	²

C. Body parts and organs

Connected to	Kind of connection	Evidence status	Context	Studies
Skin	Adverse effect or risk	Case report	Case report of allergic contact dermatitis (title only). Preparation or compound: Guava tea	¹⁴
Uterus		Not enough evidence	Relaxed rat uterine muscle in the lab. Preparation or compound: Leaf aqueous extract	²

I. Biomarkers

Connected to	Kind of connection	Evidence status	Context	Studies
Time to return to normal stools	Biological association	Low certainty	Measured in trials: shortened. A lab change is not the same as a health benefit.	^{1 15}
Abdominal pain during diarrhoea	Biological association	Low certainty	Measured in trials: shortened. A lab change is not the same as a health benefit.	^{13 12}
Blood glucose 2 hours after a meal	Biological association	Low certainty	Measured in trials: lowered. A lab change is not the same as a health benefit.	³
Fasting glucose and HbA1c	Biological association	Not enough evidence	Measured in trials: mixed. A lab change is not the same as a health benefit.	³
Insulin, C-peptide and HOMA-IR	Biological association	Not enough evidence	Measured in trials: lowered. A lab change is not the same as a health benefit.	³
Total cholesterol and triglycerides	Biological association	Not enough evidence	Measured in trials: lowered (subgroups only). A lab change is not the same as a health benefit.	³
Knee pain and stiffness scores (JKOM, visual analogue scale)	Biological association	Very low certainty	Measured in trials: lowered. A lab change is not the same as a health benefit.	⁹

J. Genes, receptors and enzymes

Connected to	Kind of connection	Evidence status	Context	Studies
Alpha-glucosidase (starch digestion)	Preliminary mechanism	In vitro	Blocked by guava leaf extract in the test tube; basis for the after-meal glucose trials.	^{3 8}
CYP2C8, CYP2C9, CYP3A4	Preliminary mechanism	In vitro	Weakly blocked in the test tube; human interaction not studied.	³

L. Active compounds

Connected to	Kind of connection	Evidence status	Context	Studies
Quercetin	Biological association	In vitro	Suspected active antidiarrhoeal compound together with its sugar forms; blocks CYP enzymes more strongly than the whole leaf extract in the lab. Preparation or compound: leaf	^{12 13 3 18}
Guaijaverin	Biological association	In vitro	Isolated from guava leaf; listed among the antidiarrhoeal or antibacterial compounds in the 2024 review. Preparation or compound: leaf	^{12 18}
Avicularin	Biological association	In vitro	Listed among compounds present in guava in the 2024 review. Preparation or compound: leaf	^{12 18}
Ellagic acid	Biological association	In vitro	Listed among compounds in the 2024 review. Preparation or compound: leaf	^{12 18}
Guavin B (an ellagitannin)	Biological association	In vitro	Tannins from guava (guavins A to D) are named in the reference list of the tea-maker's review; their role in glucose or gut effects was not read. Preparation or compound: leaf	^{3 18}

Each connection is stored with the ingredient, the connected record, the kind of connection, the evidence status, the supporting studies, the preparation or compound involved, and a review date (last reviewed October 25, 2026).

Evidence at a glance: what changed in 4 lab markers

Tap a number to show only those markers. Counts are markers, not people.

Other31

The evidence

The research centre for Guava leaf. Every record here was checked against PubMed or the publisher's page; we never list a study we have not verified.

Evidence by outcome

Short bouts of infectious diarrhoea in adults (leaf decoction) 3 studies · 109 people in trials Low certainty Belly pain with diarrhoea (standardised leaf capsule) 2 studies · 100 people in trials Low certainty Diarrhoea from rotavirus in babies and young children 2 studies · 62 people in trials Very low certainty Blood sugar after a meal (leaf tea, single serving) 2 studies Low certainty Longer-term blood sugar and insulin (HbA1c, fasting glucose, insulin) 2 studies Not enough evidence Cholesterol and triglycerides (leaf tea) 1 study Not enough evidence Antibacterial and gut-calming effects in the lab (animal and test-tube only) 3 studies Not enough evidence Knee pain (leaf extract, 12 weeks) 1 study Very low certainty Period pain (traditional use; rat-tissue work only) 1 study Not enough evidence Cough, allergy, pain, antioxidant and other lab findings 3 studies Not enough evidence

Bars show how many studies we found for each outcome, not how well it works. People are added up across trials only (reviews are not added, to avoid double counting).

How we rate evidence

High certainty

Several well-run trials or reviews agree; further research is unlikely to change the picture much.

Moderate certainty

Good trials point the same way, but some doubt remains.

Low certainty

Small, short or inconsistent trials. The finding could change with better research.

Very low certainty

Very little or very weak human data. Treat as a possibility only.

Mixed findings

Trials or reviews disagree with each other.

Not enough evidence

Not enough human research to say either way.

Evidence against

Good research found no benefit, or found harm.

We take the reviewers' own risk-of-bias and GRADE statements where they exist, and otherwise judge from study size, design, consistency, directness and whether a product matches what is sold. Many publications do not make evidence high. Method note: We started from our earlier guava leaf summary, read PubMed abstracts for every PubMed record cited (one case report had no abstract and is marked), read the full text of two reviews through Europe PMC, and checked names in GBIF and NCBI Taxonomy and compounds in PubChem. Regulator pages that could not be opened are marked not verified.

Study library: every study we checked 19

Design Research type Plant part Year from Search

Study	Design	People	Product, dose, length	Result
Birdi 2020 A randomized open label efficacy clinical trial of oral guava leaf decoction in patients with acute infectious diarrhoea. J Ayurveda Integr Med · PMID 32507357 · DOI	Controlled trial	109 Adults aged 18 to 60 with acute infectious diarrhoea (137 enrolled, 109 included; 57% women), India	Guava leaf decoction (Indian Sardar variety), 6-leaf, 10-leaf and 14-leaf versions leaf Taken three times a day; the 14-leaf version was about 7.4 g of leaf. Trial amounts, not advice. 5 days · vs Oral rehydration solution alone	The 14-leaf decoction worked best. People returned to normal in about 72 hours versus 120 hours with oral rehydration solution alone. Haemoglobin, liver and kidney tests stayed normal and no adverse events were reported. About 72 hours versus 120 hours to normal (the abstract gives no confidence interval). Methods, limits and funding Outcomes: Stool frequency and stool consistency; blood haemoglobin, liver and kidney tests for safety Limitations: Open label (people knew what they took), registered after the trial began (retrospective registration), adults with uncomplicated diarrhoea of unknown cause only. The abstract does not give funding. The dose arms and control were compared on a modest number of people. Registration: CTRI/2016/07/007095 (retrospective) Read: abstract
Chiwororo 2009 Spasmolytic effect of Psidium guajava Linn. (Myrtaceae) leaf aqueous extract on rat isolated uterine horns. J Smooth Muscle Res · PMID 19377271 · DOI	Animal research animal	Isolated rat uterus tissue	Guava leaf aqueous extract (0.5 to 4.0 mg/mL in the tissue bath) leaf	The extract reduced spontaneous contractions and blocked contractions caused by acetylcholine, oxytocin, bradykinin, carbachol and potassium in a dose-related way. Lab (rat tissue) only. Methods, limits and funding Outcomes: Strength of uterine muscle contractions Limitations: Animal tissue in a dish; no human data. The authors link it to traditional use for period pain, which is not proof of effect in women. Read: abstract
Deguchi 2010 Anti-hyperglycemic and anti-hyperlipidemic effects of guava leaf extract. Nutr Metab (Lond) · PMID 20181067 · DOI	Narrative review	Review of lab work, animal models and several small clinical trials of Guava Leaf Tea (people with pre-diabetes and type 2 diabetes)	Aqueous guava leaf extract and Guava Leaf Tea (Bansoureicha, Yakult Honsha, Japan) leaf	In a crossover trial in 20 hospitalised people with type 2 diabetes, a single serving of Guava Leaf Tea lowered the glucose 2 hours after a meal from about 160 mg/dL to 143 mg/dL, and the drug voglibose to 133 mg/dL; the tea effect was milder than the drug (p<0.01). No hypoglycaemia was seen when the tea was combined with usual treatment. In a 12-week study in 15 men with pre-diabetes or mild type 2 diabetes, fasting glucose fell from 136 to 131 mg/dL (p=0.07); 5 of 7 pre-diabetic men had lower HbA1c; insulin, C-peptide and HOMA-IR fell significantly; cholesterol and triglycerides fell only in small subgroups with high starting values. The review also reports no hypoglycaemia in people on diabetes medicines, no change in liver, kidney or iron tests, and no toxicity in rats. Single serving: about 160 to 143 mg/dL (tea) versus 133 mg/dL (voglibose). 12 weeks: fasting glucose 136 to 131 mg/dL, not significant (p=0.07). Methods, limits and funding Outcomes: After-meal blood glucose, fasting glucose, HbA1c, insulin, lipids, safety, drug interaction tests Limitations: Narrative review by employees of the company that makes the tea; one author declares patents on Guava Leaf Tea. Trial details are secondhand through the review. Small trials, several uncontrolled. Interaction tests were in vitro or in rodents. Funding and conflicts: Authors from Yakult Central Institute; Y. Deguchi holds patents covering uses of Guava Leaf Tea (declared). Industry-linked. Read: full-text (via Europe PMC)
Dibaba 2026 Acute and sub-acute toxicological studies on the ethanol leaf extract of Psidium guajava in experimental mice. Pan Afr Med J · PMID 42283039 · DOI	Animal research animal	Mice	Guava leaf ethanol extract leaf Up to 2000 mg/kg once or up to 1000 mg/kg a day in mice 28 days (sub-acute)	No deaths or signs of acute toxicity at 2000 mg/kg, and no treatment-related changes in blood, biochemistry or tissue at 1000 mg/kg a day for 28 days. Mouse safety study only. Methods, limits and funding Outcomes: Deaths, blood tests, organ weight and tissue changes Limitations: Mice, ethanol extract. Does not tell us the human safe range. Read: abstract
Disler 1975 The effect of tea on iron absorption. Gut · PMID 1168162 · DOI	Clinical trial	Human volunteers	Ordinary tea (Camellia sinensis), not guava leaf (tea)	Tea inhibited absorption of non-haem iron, which the authors ascribed to insoluble iron tannate complexes. Drinking tannin-containing drinks with meals may contribute to iron deficiency if the diet is mostly plant food. Methods, limits and funding Outcomes: Absorption of non-haem iron from solutions and meals Limitations: This is about black tea, not guava leaf. We found no iron study of guava leaf tea; it is used here only as a related warning for tannin-rich drinks. Read: abstract
Garrido 2024 Antidiarrheal effect of Psidium guajava L. extract in acute diarrhea: a systematic review. J Sci Food Agric · PMID 38578668 · DOI	Systematic review	Reviewed 23 articles up to 2021 (20 preclinical, 3 clinical trials)	Guava (Psidium guajava) galenic preparations and phytopharmaceuticals mixed (mainly leaf)	Of 23 articles, 20 (87%) were preclinical and only 3 (13%) were clinical trials. Most studies reported positive results and mechanistic evidence (antibacterial, anti-motility, anti-secretory, anti-inflammatory). The authors say more studies are needed to define the clinical importance and safety. No pooled effect; narrative systematic review. Methods, limits and funding Outcomes: Antidiarrhoeal, antibacterial, antispasmodic effects; clinical efficacy, dose and safety Limitations: Mostly animal and lab studies. Only three human trials. No pooled analysis. Searches stopped at 2021. Only the abstract was read. Read: abstract
Gutierrez 2008 Psidium guajava: a review of its traditional uses, phytochemistry and pharmacology. J Ethnopharmacol · PMID 18353572 · DOI	Narrative review mixed	Narrative review, mostly lab and animal studies	Psidium guajava leaves, fruit and other parts mixed	Guava is mainly known for antispasmodic and antimicrobial use in diarrhoea and dysentery and has been used widely as a glucose-lowering agent. Lab and animal studies report antioxidant, liver-protective, anti-allergy, antimicrobial, anti-cough, anti-inflammatory and pain-reducing activity. The authors suggest clinical uses for infant rotavirus diarrhoea, diarrhoea and diabetes. Methods, limits and funding Outcomes: Traditional uses, chemistry and pharmacology Limitations: Abstract only. Mostly lab and animal evidence; the review was written in 2008 and predates later trials. Read: abstract
Hsu 2024 Functional assessments of Psidium guajava L. and Morus alba L. leaf extracts on postprandial glucose control. Food Sci Nutr · PMID 39055216 · DOI	In vitro animal in-vitro	Test-tube enzyme tests, liver cell line, normal and diabetic rats	Guava and mulberry leaf extracts, alone and mixed leaf · vs Glucobay (acarbose) as a reference	In the test tube, guava leaf extract blocked the starch-digesting enzyme alpha-glucosidase (IC50 2.25 mg/mL) less strongly than mulberry (0.1 mg/mL) but more strongly than acarbose (6.41 mg/mL, in the same test). The mixture did not harm a mouse liver cell line. Lab and rat data only. Methods, limits and funding Outcomes: Alpha-glucosidase inhibition, after-meal glucose in rats, cell toxicity Limitations: No human data. Test-tube strength does not predict an effect in people. Read: abstract
Kakuo 2018 Effects of Psidium guajava Linn. leaf extract in Japanese subjects with knee pain: a randomized, double-blind, placebo-controlled, parallel pilot study. Aging Clin Exp Res · PMID 29687303 · DOI	Controlled trial	Japanese adults with knee pain and no prior knee treatment (number of people not stated in the abstract)	Guava leaf extract (a standardised commercial extract; details not in the abstract) leaf 1 g a day. Trial amount, not advice. 12 weeks · vs Placebo	At week 12 the guava group had lower pain and stiffness scores (a JKOM subcategory) and lower knee pain on the visual scale than placebo. Significant differences at week 12; numbers not given in the abstract. Methods, limits and funding Outcomes: Japanese Knee Osteoarthritis Measure (JKOM) score and a visual analogue scale for knee pain Limitations: Pilot study; the number of participants, effect sizes, funding and who made the extract are not in the abstract. Short follow-up. Only the abstract was read. Read: abstract
Kaur 2025 A Comprehensive Review of the Effects of Psidium guajava and Syzygium cumini Leaves on Diabetes Mellitus. Prev Nutr Food Sci · PMID 40612758 · DOI	Narrative review	Narrative review of two leaves (guava and jamun)	Psidium guajava and Syzygium cumini leaves leaf	The abstract says both leaves show glucose-lowering, antioxidant and anti-inflammatory properties linked to quercetin, rutin and gallic acid. It describes no human trial. Methods, limits and funding Outcomes: Blood sugar, antioxidant and anti-inflammatory effects Limitations: Abstract only. Reviews lab and animal findings; calls the leaves "substitutes for synthetic drugs", which is a stronger claim than human data support. Read: abstract
Kumari 2016 Effect of Guava in Blood Glucose and Lipid Profile in Healthy Human Subjects: A Randomized Controlled Study. J Clin Diagn Res · PMID 27790420 · DOI	Controlled trial	45 Healthy medical students, India	Ripe guava FRUIT (with or without peel), not leaf fruit 400 g of fruit a day. Trial amount, not advice. 6 weeks · vs No supplement (control group)	Fruit with peel raised fasting glucose, cholesterol and triglycerides; fruit without peel lowered cholesterol, triglycerides and LDL, with no significant glucose change. Methods, limits and funding Outcomes: Fasting glucose, cholesterol, triglycerides, BMI, blood pressure Limitations: This is about the fruit, not the leaf. Healthy students, small groups. Kept only to show that fruit results do not carry over to leaf tea. Read: abstract
Liu 2024 Ethnobotany, phytochemistry, and biological activities of Psidium guajava in the treatment of diarrhea: a review. Front Pharmacol · PMID 39246650 · DOI	Systematic review	189 studies (ethnobotany, lab, animal and clinical) up to October 2022	Psidium guajava, mainly leaf decoctions leaf	Guava is used for diarrhoea in 44 countries and the leaf is the most cited part, usually as a decoction. About 27 antidiarrhoeal or antibacterial compounds were identified, including flavonoids such as quercetin and its glycosides. The review also describes two clinical trials: Birdi 2020 (decoction) and Lozoya 2002 (standardised capsule). It says it is still unknown whether quercetin and its glycosides are the only active compounds, how the plant works, and whether guava leaves are safe in all groups including children, and at what amounts. No pooled effect; narrative review. Methods, limits and funding Outcomes: Traditional use, lab and animal antidiarrhoeal activity, safety and clinical trials Limitations: Mostly lab and animal evidence. Full text read for the clinical, safety and toxicology parts; not every cited study was opened. Excludes journals with impact factor below 1.0. Read: full-text
Lozoya 2002 Intestinal anti-spasmodic effect of a phytodrug of Psidium guajava folia in the treatment of acute diarrheic disease. J Ethnopharmacol · PMID 12413703 · DOI	Controlled trial	100 Adults with acute diarrhoea, Mexico (the abstract says 50 patients were given the product; the 2024 Liu review says 100 patients, 50 per group, aged 20 to 96)	QG-5, a guava leaf phytodrug standardised to quercetin content, in capsules leaf One 500 mg capsule every 8 hours. Trial amount, not advice. 3 days · vs Placebo capsules	The guava product shortened the duration of abdominal pain (fewer pain episodes from day 2). The 2024 Liu review adds that stool consistency and frequency did not differ from placebo. Pain duration reduced; no change in stool frequency or consistency (per the Liu review). No numbers in the abstract. Methods, limits and funding Outcomes: Abdominal pain episodes, stool consistency and frequency Limitations: Abstract only for the trial; the stool result comes from the 2024 review. Small trial. Funding is not stated in the abstract. Read: abstract
Obi 2001 Allergic contact dermatitis due to guava tea. Contact Dermatitis · PMID 11205393 · DOI	Case report	1 Case report (details not available; PubMed has no abstract)	Guava tea leaf (presumed; not stated in the record)	The title reports allergic contact dermatitis caused by guava tea. Methods, limits and funding Outcomes: Skin allergy Limitations: PubMed record has no abstract, so only the title is known. We could not read the case. Cause and route (touching versus drinking) are not verified. Read: title-only
Wei 2000 Clinical study on treatment of infantile rotaviral enteritis with Psidium guajava L. Zhongguo Zhong Xi Yi Jie He Za Zhi · PMID 11938857	Controlled trial	62 Babies and young children with rotavirus diarrhoea, China (62 patients)	Psidium guajava preparation (the abstract does not describe the form) unspecified · vs Gegen Qinlian decoction (a Chinese herbal formula; not a placebo)	Recovery within 3 days was 87.1% with guava versus 58.1% with the comparison decoction. Diarrhoea stopped in 25.1 hours versus 38.7 hours. Rotavirus antigen cleared in 87.1% versus 58.1%. 87.1% versus 58.1% recovered in 3 days (P<0.05); 25.1 versus 38.7 hours (P<0.01). Methods, limits and funding Outcomes: Time to stop diarrhoea, blood sodium, stool sodium and glucose, rotavirus antigen clearance Limitations: Small, 25 years old, in a Chinese-language journal. The comparison was another herbal decoction, not oral rehydration alone or placebo. Preparation, plant part and ages are not in the abstract. Randomisation and blinding methods not stated. Only the abstract was read. Read: abstract
s-gbif GBIF species match: Psidium guajava L. · Source	Database record reference			Methods, limits and funding Read: read (API, 2026-10-25)
s-ncbi-tax NCBI Taxonomy: Psidium guajava · Source	Database record reference			Methods, limits and funding Read: read (E-utilities, 2026-10-25)
s-pubchem PubChem compound records (quercetin, guaijaverin, avicularin, ellagic acid, guavin B) · Source	Database record reference			Methods, limits and funding Read: read (PUG REST, 2026-10-25)
s-regulators-notfound Regulator and reference checks for guava leaf (no entry found) · Source	Database record reference			Methods, limits and funding Read: searched (2026-10-25)

What we do not know yet

No large placebo-controlled trial of guava leaf for diarrhoea in adults or children.
No independent long-term trial for blood sugar.
No human interaction, pregnancy, breastfeeding or child safety data.
No product-quality analysis; decoction, tea and extract are not compared.

How new research is added

New studies are found by a saved PubMed search and placed in a review queue. A person reads each one before it changes any rating or safety wording.

Lab markers

What changed in blood or saliva tests during trials. A changed number is not the same as feeling or being healthier, and we give no "normal ranges".

Other 7

●

Time to return to normal stools

Shortened in trials

How many hours or days acute diarrhoea lasts before stools are normal.

Low certainty

Results and what it means

Why it was measured

The main outcome in the diarrhoea trials.

Statistical vs. clinical meaning

Faster recovery in two small trials, one open-label and one with an active herbal comparison.

Safety implication

Dehydration risk if rehydration is delayed.

Study	Result	People	Product
¹	About 72 hours with the 14-leaf decoction versus 120 hours with oral rehydration solution alone.	109 adults with acute infectious diarrhoea	Guava leaf decoction (14 leaves), 5 days
¹⁵	Diarrhoea stopped in 25.1 versus 38.7 hours (P<0.01) against a herbal comparison decoction.	62 infants with rotavirus diarrhoea	Guava preparation (form not described)

^{1 15}

●

Abdominal pain during diarrhoea

Shortened in trials

How long belly pain lasts during acute diarrhoea.

Low certainty

Results and what it means

Why it was measured

The outcome that improved in the standardised-capsule trial.

Statistical vs. clinical meaning

A single positive result in one small double-blind trial.

Safety implication

None identified from this measure.

Study	Result	People	Product
¹³	Duration of abdominal pain was shorter with the guava capsule than with placebo; stool frequency and consistency did not change (per the Liu review).	Adults with acute diarrhoea (50 given the product)	Standardised guava leaf capsule (QG-5), 3 days

Study	Result	People	Product
⁹	Pain and stiffness subscore and visual analogue scale pain were lower than placebo at week 12 (numbers not in the abstract).	Japanese adults with knee pain	Guava leaf extract daily for 12 weeks

⁹

Safety

What studies and official sources say about side effects, medicines and who should check first. Each point shows what kind of evidence it comes from.

Main points to know 5

Guava leaf looks well tolerated in the small trials, but human safety data are thin. The adult diarrhoea trial reported no adverse events and normal haemoglobin, liver and kidney tests. The tea-maker's review reports no abnormal liver, kidney or iron tests in its studies. The 2024 Liu review says it is still unknown whether guava leaves are safe in all groups, including children, and at what amounts. No regulator monograph was found. Clinical trial ^{1 3 12 19}
Blood sugar: possible added effect with diabetes medicines. Guava leaf tea lowers the rise in blood sugar after a meal in small trials. The tea-maker's review reports no low blood sugar when the tea was combined with usual diabetes treatment, but those trials were small and the review is industry-linked. A stronger combined effect cannot be ruled out. Talk to your doctor or pharmacist before using it if you take diabetes medicines, and do not change prescribed treatment on your own. Clinical trial ³
Diarrhoea in babies and children, or with fever or blood, needs medical care. Acute diarrhoea is a leading cause of illness and death in children, mostly through dehydration. Guava leaf is not a replacement for oral rehydration solution, and its safety in children is unanswered. Bloody diarrhoea, high fever, severe pain, signs of dehydration, or diarrhoea lasting more than a few days should be seen by a doctor, because stopping the gut moving can be harmful in some infections. Authoritative guidance ^{6 12}
Tannins can reduce iron absorption and may be constipating. Guava leaf contains tannins (the leaf is a source of complex tannins such as the guavins, per the references in the tea-maker's review). Ordinary tea, which is also rich in tannins, reduced absorption of non-haem iron in volunteers. We found no iron study of guava leaf tea itself, and no report of constipation. This is a reasoned caution, not a documented problem for guava leaf. Pharmacological theory ^{5 3}
Pregnancy and breastfeeding: no safety data. No study of guava leaf in pregnant or breastfeeding women was found, and no LactMed entry. In the lab, a leaf extract relaxed rat uterine muscle and blocked oxytocin-induced contractions, which is a theoretical reason for caution. Avoid medicinal amounts and ask your doctor or midwife. Animal research ^{2 19}

Side effects 4

Effect	How often	Severity and recovery	Evidence
Allergic skin reaction (contact dermatitis) from guava tea Only the title of a 2001 case report was available (no abstract), so we do not know the details.	Not established	mild to moderate Not stated (only the title is available)	Case report ¹⁴
No adverse events in the adult diarrhoea trial (109 adults, 5 days) Open-label trial; haemoglobin, liver and kidney tests normal. Short course only.	0 reported	none reported Not applicable	Clinical trial ¹
No diarrhoea or low blood sugar with larger tea volumes in healthy people (reported secondhand) Reported in the tea maker's review. Not read in the original trial.	Not established	none reported Not applicable	Clinical trial ³
Possible lower blood sugar when combined with diabetes medicines None observed in the reported trials; not excluded.	Not established	unknown Usually reversible with treatment, but low blood sugar can be dangerous	Pharmacological theory ³

Liver

No LiverTox entry for guava was found, and PubMed searches did not find a human case of liver injury from guava leaf. In the adult diarrhoea trial, liver tests stayed normal, and the tea-maker's review reports no abnormal liver tests in its tea trials. Mouse and rat studies found no liver changes at the doses tested. ^{1 3 4 19}

How often. Unknown. Absence of reports is not proof of safety: guava leaf is used by relatively few people in the countries that publish case reports.

Monitoring. No agency monitoring advice was found. Tell a doctor about yellow eyes or skin, dark urine, or unusual tiredness.

This is a safety connection. It is not evidence that Guava leaf supports liver health.

Medicines and supplements 5

With	Why it matters	Importance	Evidence	What to do
Diabetes medicines (insulin, sulfonylureas, metformin and others) prescription	Guava leaf may slow carbohydrate digestion and lower the after-meal glucose rise, so it could add to glucose-lowering drugs.	The tea-maker's review reports no low blood sugar in people taking diabetes medicines and in mice given the drugs with the extract, but studies are small and industry-linked. No independent interaction study was found.	Clinical trial Very low certainty ³	If you take diabetes medicines, ask your doctor or pharmacist before using guava leaf, and watch for signs of low blood sugar (shaking, sweating, hunger, confusion).
Alpha-glucosidase inhibitor drugs (acarbose, voglibose) prescription	Both slow digestion of starch. Guava leaf extract blocked the same enzymes in the test tube.	In a hospital crossover trial the tea lowered after-meal glucose less than voglibose, with no low blood sugar reported when combined. In mice the combination did not cause low blood sugar.	Clinical trial Very low certainty ^{3 8}	Do not combine these drugs with leaf products without your doctor's agreement.
Drugs processed by liver enzymes (CYP2C8, CYP2C9, CYP3A4), for example warfarin or some blood pressure and cholesterol drugs prescription	Guava leaf contains quercetin-type compounds that can block these enzymes in the test tube.	In test-tube tests the leaf extract blocked these enzymes at least 10 times less strongly than quercetin or grapefruit juice, and a one-month rat study showed no enzyme induction. The authors (tea maker) conclude interactions are unlikely. No human interaction study was found.	Laboratory research Very low certainty ³	People on narrow-margin medicines such as warfarin should ask a pharmacist before using concentrated extracts.
Iron supplements and iron-poor diets supplement	Tannins in tea bind non-haem iron and reduce its absorption (shown for ordinary tea).	Not tested for guava leaf. Matters most for people with iron deficiency or anaemia.	Pharmacological theory Very low certainty ⁵	If you have iron deficiency, ask a doctor or pharmacist about timing tannin-rich drinks away from iron.
Other herbs and foods that lower blood sugar (for example bitter melon, gymnema, cinnamon, mulberry leaf) herb	Adding glucose-lowering effects.	No study combined guava leaf with another herb for this use. Theoretical.	Pharmacological theory Very low certainty ³	Do not stack several blood-sugar herbs without medical advice, especially if you take diabetes medicines.

Who should check first 9

Situation	Advice	Evidence
Allergy to guava leaf or guava tea, or a past skin reaction to it	Do not use. A case report links guava tea to allergic contact dermatitis.	Case report ¹⁴
Diabetes treated with insulin or tablets	Ask your doctor or pharmacist first. Do not change or stop prescribed treatment. Check your blood sugar as advised.	Clinical trial ³
Planned surgery or anaesthesia	Tell your surgical team. Because guava leaf may lower blood sugar after meals, some teams ask people to stop herbal products that affect blood sugar before surgery. No guava-specific surgical guidance was found; this is a general precaution.	Pharmacological theory ³
Babies, children and older or frail people with diarrhoea	Use oral rehydration solution and see a doctor. Safety of guava leaf in children is unanswered (Liu 2024).	Authoritative guidance ^{12 6}
Diarrhoea with blood, high fever, severe pain, signs of dehydration or lasting more than a few days	Needs medical care. A herbal remedy that slows the gut or acts as an astringent should not delay it.	Authoritative guidance ⁶
Iron deficiency or anaemia	Tannin-rich drinks can reduce iron absorption (shown for tea). Ask a doctor or pharmacist.	Pharmacological theory ⁵
Pregnancy and breastfeeding	Avoid medicinal amounts. No human safety data; a leaf extract relaxed rat uterus tissue in the lab. No LactMed entry was found.	Animal research ^{2 19}
Liver or kidney disease	Ask a doctor first. Trials report normal liver and kidney tests in healthy or mildly ill people, but people with disease were not studied.	Other ^{1 3}
Chronic constipation or bowel narrowing	Be cautious. Leaf products used to stop diarrhoea could in theory worsen constipation. No report was found.	Pharmacological theory ¹²

Overdose, product quality and regulators

Summary. Guava leaf has been used for a very long time as food-like tea and folk medicine. Rodent studies found no toxicity at high doses, but there are no formal human toxicity studies. Safe amounts have not been defined.

Animal. Rats given a guava leaf extract up to 6,000 mg/kg showed no deaths in an acute test (reported in the Liu review). A 2026 mouse study found no toxicity at 2,000 mg/kg once and no treatment-related changes at 1,000 mg/kg a day for 28 days. The tea-maker's review reports no toxicity in rats at 200 and 2,000 mg/kg a day for a month.

Human doses studied. Trials used a leaf decoction for 5 days, a standardised capsule for 3 days, and a commercial tea for up to 12 weeks. These are trial amounts, not advice.

Overdose response. No overdose cases were found. A review reports that a larger volume of tea did not cause diarrhoea or low blood sugar in healthy people (secondhand).

Genotoxicity. The tea maker's review reports no mutagenic activity of the extract in a bacterial test (Ames) and no chromosome damage in a mouse test. Independent confirmation was not found.

Toxic plant parts. The leaf is the studied part. A brine-shrimp test classed one bark extract as toxic and a root extract as more harmful than a leaf extract, so bark and root should not be assumed to share the leaf's safety (Liu 2024).

No analysis of guava leaf products for contaminants or adulteration was found. Content varies between a home decoction, a commercial tea and a standardised extract.

Different products are not interchangeable. The trials used a leaf decoction (Birdi), a quercetin-standardised capsule (Lozoya) and a commercial tea made from an aqueous extract (Deguchi). Results from one do not apply to another. ^{1 13 3}

Leaves from sprayed or roadside trees. Plants can carry pesticide or heavy-metal residues. No test of guava leaf products was found, so this is a general precaution. ¹⁹

Body	Action	Date

When to get medical help

A baby or child with diarrhoea who is drowsy, very thirsty, not passing urine, or has sunken eyes: seek medical care urgently.
Bloody or black stools, high fever, severe or constant belly pain, or diarrhoea lasting more than a few days: see a doctor.
Shakiness, sweating, fast heartbeat, confusion or fainting if you take diabetes medicines: treat low blood sugar as your care plan says and call your doctor.
Itchy rash, swelling or blistering after handling guava leaf or drinking the tea: stop and see a doctor.
Yellow eyes or skin, dark urine, or unusual tiredness: see a doctor.

Stop the supplement and contact a clinician or emergency service. In the US, Poison Control is 1-800-222-1222.

General information only, not medical advice. Ask a clinician or pharmacist before use, especially with medicines, in pregnancy or with a health condition. See the Natural Remedy Safety guide.

Frequently asked questions

What is guava leaf?

It is the leaf of the guava tree (Psidium guajava), used as a tea, a simmered drink or an extract for diarrhoea and, more recently, blood sugar.

^{16 12}

Does guava leaf stop diarrhoea?

One open-label trial in 109 adults found recovery in about 3 days versus about 5 days with oral rehydration alone, and a capsule trial found less belly pain but no change in stools. The evidence is small. Oral rehydration comes first.

^{1 13 6}

Is it safe for children with diarrhoea?

That is not known. A 2024 review says safety in children is an open question, and the one infant trial was small and old. Use oral rehydration solution and see a doctor, because children can dehydrate fast.

^{12 15}

Does guava leaf lower blood sugar?

Small trials of a Japanese guava leaf tea lowered the blood sugar rise after a meal, less than the drug voglibose. Long-term benefit has not been shown, and the main review is by the tea maker.

Can it cause low blood sugar with diabetes drugs?

No low blood sugar was reported in the tea maker's review of people on usual treatment, but studies were small. A stronger combined effect cannot be ruled out, so ask your doctor or pharmacist first.

Should I stop it before surgery?

Tell your surgical team. Because it may lower blood sugar, some teams ask people to pause herbs that affect blood sugar. We found no guava-specific surgical guidance; this is a general precaution.

Is it safe in pregnancy or breastfeeding?

No safety data exist. A leaf extract relaxed rat uterus tissue in the lab. Avoid medicinal amounts and ask your doctor or midwife.

^{2 19}

Can the tannins cause constipation or affect iron?

Ordinary tea reduced iron absorption in volunteers, and tannin-rich leaf teas could in theory be constipating. No study of guava leaf tea has tested either, so ask a pharmacist if you have iron deficiency.

^{5 3}

Does it interact with other medicines?

Test-tube tests suggest only weak effects on liver enzymes that process many drugs, but no human interaction study exists. People on warfarin or other narrow-margin drugs should ask a pharmacist.

Can it harm the liver or kidneys?

Liver and kidney tests stayed normal in the trials, and no human liver injury report was found, but people with liver or kidney disease were not studied. Absence of reports is not proof of safety.

^{1 3 19}

Is guava leaf the same as guava fruit?

No. It is a different part of the same tree, and results for one do not apply to the other. See the guava fruit page.

^{11 12}

When should I see a doctor?

For bloody diarrhoea, high fever, severe pain, signs of dehydration, diarrhoea lasting more than a few days, any child or baby with diarrhoea, shakiness or confusion on diabetes medicines, or an itchy rash after contact. Ask a doctor or pharmacist about amounts and your medicines.

^{6 3 14}

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Editorial transparency

Written by: AlternativeMed editorial team. Research compiled with AI assistance, then checked against PubMed records.
Medical review: None. This page has not been reviewed by a physician or pharmacist.
First published: 2026-10-25
Last substantive update: 2026-10-25
How we research: We started from our earlier guava leaf summary, read PubMed abstracts for every PubMed record cited (one case report had no abstract and is marked), read the full text of two reviews through Europe PMC, and checked names in GBIF and NCBI Taxonomy and compounds in PubChem. Regulator pages that could not be opened are marked not verified.
How we rate evidence: See "How we rate evidence" in the Evidence tab.
Independence: No product is promoted on this page. No affiliate links are shown.

Sources 19

Each source was opened and checked. Where we read only the abstract, it says so. The small numbers in the text point here.

Birdi T, Krishnan GG, Kataria S, Gholkar M, Daswani P. A randomized open label efficacy clinical trial of oral guava leaf decoction in patients with acute infectious diarrhoea.. J Ayurveda Integr Med. 2020. PMID 32507357. DOI 10.1016/j.jaim.2020.04.001. (abstract)
Chiwororo WD, Ojewole JA. Spasmolytic effect of Psidium guajava Linn. (Myrtaceae) leaf aqueous extract on rat isolated uterine horns.. J Smooth Muscle Res. 2009. PMID 19377271. DOI 10.1540/jsmr.45.31. (abstract)
Deguchi Y, Miyazaki K. Anti-hyperglycemic and anti-hyperlipidemic effects of guava leaf extract.. Nutr Metab (Lond). 2010. PMID 20181067. DOI 10.1186/1743-7075-7-9. (full-text (via Europe PMC))
Dibaba GT, Leminie AA, Tadesse WH, et al.. Acute and sub-acute toxicological studies on the ethanol leaf extract of Psidium guajava in experimental mice.. Pan Afr Med J. 2026. PMID 42283039. DOI 10.11604/pamj.2026.53.49.49406. (abstract)
Disler PB, Lynch SR, Charlton RW, Torrance JD, Bothwell TH, Walker RB. The effect of tea on iron absorption.. Gut. 1975. PMID 1168162. DOI 10.1136/gut.16.3.193. (abstract)
Garrido G, Garrido-Suarez BB, Martinez-Tapia N, et al.. Antidiarrheal effect of Psidium guajava L. extract in acute diarrhea: a systematic review.. J Sci Food Agric. 2024. PMID 38578668. DOI 10.1002/jsfa.13515. (abstract)
Gutierrez RM, Mitchell S, Solis RV. Psidium guajava: a review of its traditional uses, phytochemistry and pharmacology.. J Ethnopharmacol. 2008. PMID 18353572. DOI 10.1016/j.jep.2008.01.025. (abstract)
Hsu YP, Chen WY, Hsieh PC, Chu YL. Functional assessments of Psidium guajava L. and Morus alba L. leaf extracts on postprandial glucose control.. Food Sci Nutr. 2024. PMID 39055216. DOI 10.1002/fsn3.4175. (abstract)
Kakuo S, Fushimi T, Kawasaki K, Nakamura J, Ota N. Effects of Psidium guajava Linn. leaf extract in Japanese subjects with knee pain: a randomized, double-blind, placebo-controlled, parallel pilot study.. Aging Clin Exp Res. 2018. PMID 29687303. DOI 10.1007/s40520-018-0953-6. (abstract)
Kaur S, Chaudhary R. A Comprehensive Review of the Effects of Psidium guajava and Syzygium cumini Leaves on Diabetes Mellitus.. Prev Nutr Food Sci. 2025. PMID 40612758. DOI 10.3746/pnf.2025.30.3.209. (abstract)
Kumari S, Rakavi R, Mangaraj M. Effect of Guava in Blood Glucose and Lipid Profile in Healthy Human Subjects: A Randomized Controlled Study.. J Clin Diagn Res. 2016. PMID 27790420. DOI 10.7860/JCDR/2016/21291.8425. (abstract)
Liu C, Jullian V, Chassagne F. Ethnobotany, phytochemistry, and biological activities of Psidium guajava in the treatment of diarrhea: a review.. Front Pharmacol. 2024. PMID 39246650. DOI 10.3389/fphar.2024.1459066. (full-text)
Lozoya X, Reyes-Morales H, Chavez-Soto MA, Martinez-Garcia MdC, Soto-Gonzalez Y, Doubova SV. Intestinal anti-spasmodic effect of a phytodrug of Psidium guajava folia in the treatment of acute diarrheic disease.. J Ethnopharmacol. 2002. PMID 12413703. DOI 10.1016/s0378-8741(02)00185-x. (abstract)
Obi M, Miyazaki Y, Yokozeki H, Nishioka K. Allergic contact dermatitis due to guava tea.. Contact Dermatitis. 2001. PMID 11205393. DOI 10.1034/j.1600-0536.2001.44020917.x. (title-only)
Wei L, Li Z, Chen B. Clinical study on treatment of infantile rotaviral enteritis with Psidium guajava L.. Zhongguo Zhong Xi Yi Jie He Za Zhi. 2000. PMID 11938857. (abstract)
. GBIF species match: Psidium guajava L.. . . (read (API, 2026-10-25))
. NCBI Taxonomy: Psidium guajava. . . (read (E-utilities, 2026-10-25))
. PubChem compound records (quercetin, guaijaverin, avicularin, ellagic acid, guavin B). . . (read (PUG REST, 2026-10-25))
. Regulator and reference checks for guava leaf (no entry found). . . (searched (2026-10-25))

Where to buy

Check the label first. Whatever you buy, look for these:

The plant part and the extract type or ratio on the label
A standardized amount of the active compounds, where relevant
A third-party testing mark (USP, NSF or ConsumerLab)
Interactions: ask a pharmacist if you take medicines, are pregnant or have a medical condition

Talk to a pharmacist or doctor before you start any supplement, especially if you take medicines. See the Safety tab for interactions.

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Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.