Herbal Tea for People With Diabetes or High Blood Pressure
What trials and reviews found for hibiscus and chamomile tea in blood pressure and diabetes, why licorice tea is the main caution, and what to ask your prescriber.
Content last updated . This page has not been medically reviewed.
Safety first. Natural products can cause side effects and interact with medicines. Read herbal tea and extract safety before you use anything on this page.
Read this first
- Licorice can raise blood pressure. In a pooled analysis of 18 studies (337 people) that used products with at least 100 mg of glycyrrhizic acid a day, chronic licorice intake was associated with higher blood pressure and a drop in potassium, even at modest doses. [1] NIH says even small amounts of glycyrrhizin have been linked to severe adverse effects, including in people with hypertension and in people with heart or kidney conditions. [2] Licorice can be hidden in blends: see licorice in tea blends.
- Do not replace or adjust blood pressure or diabetes medicines with a tea. Ask the prescriber or pharmacist. FDA says it is not authorized to approve dietary supplements for safety and effectiveness before they are marketed. [3]
- A tea that "lowers a number" in a study is not the same as a treatment. Everything below is information, not advice.
Hibiscus tea and blood pressure
Hibiscus tea is made from Hibiscus sabdariffa L., in the mallow family. [4] Cochrane calls the plant roselle and notes it is also called sour tea or red tea. [5] See hibiscus tea.| Question | What the source found | Strength of evidence | Population and form |
|---|---|---|---|
| Does the tea lower blood pressure? | In a placebo-controlled trial, hibiscus tea lowered systolic pressure by 7.2 mm Hg versus 1.3 with placebo after 6 weeks (P = 0.030); the diastolic change did not differ from placebo. [6] | Promising but limited | 65 pre- and mildly hypertensive adults not taking blood pressure medicine; trial used 3 servings of 240 mL a day [6] |
| Do trials add up? | A meta-analysis of seven randomized trials (362 people) found a systolic pressure change of -4.71 mm Hg. [7] An umbrella review of 26 trials (1,797 people) found dose-dependent reductions in blood pressure compared with placebo and other teas. [8] | Promising but limited; forms and designs differ | Adults; the abstracts do not separate tea from other forms |
| What did Cochrane find? | The Cochrane review, which looked for trials in people with hypertension, found only one trial that qualified, and it tested roselle extract capsules in 60 people with type 2 diabetes. [5] It judged the evidence insufficient to say whether roselle lowers blood pressure in people with hypertension. [5] | Insufficient evidence | Capsules, not tea |
| Does it work alongside medicines? | A small pilot study in Jordan gave hibiscus tea to people with uncontrolled hypertension; 72% of the 29 who finished were taking blood pressure medicine. [9] | Insufficient evidence: a pilot with no comparison group described in the abstract [9] | Tea, with or without medicine |
The umbrella review also says that long-term and therapeutic-level safety requires careful monitoring. [8] Proper evidence not found for controlled human trials of hibiscus tea combined with a specific blood pressure medicine: our PubMed searches returned only the pilot above. Whether adding a blood-pressure-lowering tea to medicines lowers pressure further was not examined in the sources we read, so ask the prescriber.
Tea and blood sugar in type 2 diabetes
| Question | What the source found | Strength of evidence | Population and form |
|---|---|---|---|
| Chamomile tea | After 8 weeks, the tea group had lower HbA1c and insulin than the water group. [10] | Promising but limited; a lab marker, not a health outcome | 64 adults aged 30 to 60, single-blind; the tea was 3 g in 150 mL hot water three times a day after meals [10] |
| Herbal tea in general | A meta-analysis of 14 trials (551 people) linked drinking non-Camellia sinensis herbal tea with lower fasting glucose and HbA1c. [11] | Mixed to promising; the authors found that study features such as trial length and region explained part of the differences [11] | Adults with type 2 diabetes; many different herbs |
| Cinnamon, cardamom, ginger or saffron added to black tea | In 204 people, the herbal products did not significantly change glycemic control measures. [12] | Mixed | Adults with type 2 diabetes; black tea with a spice |
| Cinnamon | NIH says it is unclear whether cinnamon supplements help diabetes, and that studies often do not say which species or plant part was tested. [13] | Insufficient evidence | Supplements |
Proper evidence not found, in the sources we read, for herbal tea changing the effect of a specific diabetes medicine. NIH says there are theoretical reasons to suspect that dandelion might interact with antidiabetes drugs. [14] "Theoretical" means a reason for caution, not a proven harm. Results for one tea or form do not carry over to another.
What a reader can safely do
- Tell the prescriber and pharmacist which teas you drink, including blends.
- Check labels for licorice or "licorice root". See reading an herbal tea ingredient list.
- Keep monitoring routines your clinician set; do not use a tea result to decide on medicine.
- For the goal-level evidence, see herbal tea for blood pressure and heart health and herbal tea for blood sugar and cholesterol.
Frequently asked questions
Does hibiscus tea lower blood pressure?
One placebo-controlled trial found a systolic drop in people with mild high blood pressure who were not on medicine, and meta-analyses point the same way. [6][7] The Cochrane review found too little evidence in people with hypertension. [5] Evidence is promising but limited.
Can I drink hibiscus tea with blood pressure medicine?
Proper evidence not found for controlled trials of the combination. A pilot included people on medicine but had no described comparison group. [9] Ask your prescriber or pharmacist before making it a regular habit.
Is chamomile tea good for diabetes?
One 8-week trial in 64 adults found lower HbA1c with chamomile tea than with water. [10] It was a lab marker in a small trial; it does not show that tea treats diabetes.
Is licorice tea safe if I have high blood pressure?
NIH says even small amounts of glycyrrhizin have been linked to severe adverse effects in people with hypertension. [2] Ask a clinician before using it.
Can I stop my medicine if I drink these teas?
No. Do not stop or change a prescribed medicine; ask the prescriber or pharmacist.
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Licorice: why it gets its own warning
References
- Penninkilampi R, Eslick EM, Eslick GD. The association between consistent licorice ingestion, hypertension and hypokalaemia: a systematic review and meta-analysis. J Hum Hypertens. 2017. PubMed 28660884 (abstract). Read 2026-10-23.
- National Center for Complementary and Integrative Health (NIH). Licorice Root: Usefulness and Safety. Read 2026-10-23.
- U.S. Food and Drug Administration. Information for Consumers on Using Dietary Supplements. Read 2026-10-23.
- GBIF Secretariat. GBIF Backbone Taxonomy species match (accepted names checked for the plants named on these pages). Read 2026-10-23.
- Roselle for hypertension in adults. Cochrane Database of Systematic Reviews. 2021. PubMed 34837382 (abstract). Read 2026-10-23.
- McKay DL, Chen CY, Saltzman E, Blumberg JB. Hibiscus sabdariffa L. tea (tisane) lowers blood pressure in prehypertensive and mildly hypertensive adults. J Nutr. 2010. PubMed 20018807 (abstract). Read 2026-10-23.
- The efficacy of sour tea (Hibiscus sabdariffa L.) on selected cardiovascular disease risk factors: a systematic review and meta-analysis of randomized clinical trials. Phytotherapy Research. 2020. PubMed 31943427 (abstract). Read 2026-10-23.
- Norouzzadeh M, et al. Efficacy and safety of Hibiscus sabdariffa in cardiometabolic health: an overview of reviews and updated dose-response meta-analysis. Complement Ther Med. 2025. PubMed 39870328 (abstract). Read 2026-10-23.
- Treating Uncontrolled Hypertension with Hibiscus sabdariffa When Standard Treatment Is Insufficient: Pilot Intervention. J Altern Complement Med. 2019. PubMed 31599646 (abstract). Read 2026-10-23.
- Rafraf M, Zemestani M, Asghari-Jafarabadi M. Effectiveness of chamomile tea on glycemic control and serum lipid profile in patients with type 2 diabetes. J Endocrinol Invest. 2015. PubMed 25194428 (abstract). Read 2026-10-23.
- Effects of Herbal Tea (Non-Camellia sinensis) on Glucose Homeostasis and Serum Lipids in Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis. Nutrition Reviews. 2025. PubMed 38894639 (abstract). Read 2026-10-23.
- Effects of Cinnamon, Cardamom, Saffron, and Ginger Consumption on Markers of Glycemic Control, Lipid Profile, Oxidative Stress, and Inflammation in Type 2 Diabetes Patients. Review of Diabetic Studies. 2014. PubMed 26177486 (abstract). Read 2026-10-23.
- National Center for Complementary and Integrative Health (NIH). Cinnamon: Usefulness and Safety. Read 2026-10-23.
- National Center for Complementary and Integrative Health (NIH). Dandelion: Usefulness and Safety. Read 2026-10-23.
- A low dose of daily licorice intake affects renin, aldosterone, and home blood pressure in a randomized crossover trial. Am J Clin Nutr. 2024. PubMed 38246526 (abstract; 28 healthy volunteers, licorice product, not tea). Read 2026-10-23.