Biotin (Vitamin B7): Hair, Skin, Nails and Lab-Test Interference
Biotin (vitamin B7): what it does, food sources, adequate intake, the limited evidence for hair, skin and nails in healthy people, and the FDA warning about incorrect lab test results.
Content last updated . This page has not been medically reviewed.
What is Vitamin B7 good for?
What the body uses it for, and how strong the evidence is. A normal job in the body is not proof that extra supplements add benefit; each card says which.
Making fatty acids
Established roleThe body needs biotin to make fatty acids.
Supplements: Normal intake covers this role. We found no good evidence that extra biotin adds benefit in people who are not deficient.
Breaking down and using food (metabolism)
Established roleBiotin helps the body break down and use the food you eat.
Supplements: Supplements are not shown to improve metabolism when intake is adequate.
Helping enzymes that process fats, proteins and carbohydrates
Established roleBiotin is a helper for enzymes that break down fats, proteins and carbohydrates.
Supplements: Matters when these enzymes cannot work, as in inherited disorders or deficiency; no good evidence of extra benefit otherwise.
Normal growth
Established roleBiotin supports growth.
Supplements: Supplements are not shown to add benefit when the diet is adequate.
Healthy skin, hair and nails
Deficiency linkLack of biotin can cause skin rashes, hair loss and brittle nails, so the body needs enough of it for these tissues.
Supplements: Helps when hair or nail changes are caused by biotin deficiency. No proven benefit for healthy people, so a popular marketing claim is not supported.
Hormone and cholesterol production
Established roleBiotin is described as supporting the making of hormones and cholesterol.
Supplements: No evidence that supplements change hormone or cholesterol levels in people with adequate intake.
Brittle nails and uncombable hair (reported cases)
Preliminary or mixedIn a few reported cases, biotin improved brittle nails or uncombable hair.
Supplements: Preliminary only: small case reports, not enough to recommend supplements for healthy people.
Connected topics
Open a group to see how each topic connects and how strong the evidence is.
Health goals (2)
- Hair SupportPreliminary or mixed
Hair loss is a sign of biotin deficiency, and biotin helped some people whose hair problems had an underlying cause. A 2017 review found insufficient evidence for healthy people.
- Healthy SkinDeficiency link
Lack of biotin can cause skin rashes and dermatitis. We found no good evidence that extra biotin improves skin in people who are not deficient.
Body systems (4)
- Metabolism & WeightEstablished role
Biotin helps the body break down and use food and make fatty acids. We found no evidence that supplements help with weight.
- Integumentary SystemDeficiency link
Deficiency can cause skin rashes, dermatitis, hair loss and brittle nails.
- Nervous SystemDeficiency link
In the inherited disorder biotinidase deficiency, the body cannot recycle biotin, and untreated babies can have seizures, low muscle tone and developmental delay. This is a rare genetic condition, not everyday low intake.
- Skin, Hair & BeautyDeficiency link
Deficiency can cause skin rashes, hair loss and brittle nails. For healthy people the evidence for supplements is insufficient.
Body parts (3)
- HairDeficiency link
Hair loss is a sign of biotin deficiency. Evidence of benefit for healthy hair is insufficient.
- Nervous SystemDeficiency link
Seizures and low muscle tone occur in untreated inherited biotinidase deficiency, a rare genetic condition.
- SkinDeficiency link
Biotin deficiency can cause skin rashes and dermatitis.
Root causes (2)
- Nutrient DeficiencyDeficiency link
Biotin deficiency can cause skin rashes, hair loss, brittle nails and muscle pain. The 2017 review considers true deficiency uncommon in people with balanced diets.
- Medication Side EffectsPreliminary or mixed
In the 2017 review, some reported biotin deficiency cases involved valproic acid or isotretinoin. These were case reports only.
Conditions & symptoms (8)
- Biotin DeficiencyDeficiency link
Lack of biotin can cause skin rashes, hair loss, brittle nails, muscle pain, dermatitis and a swollen tongue.
- Biotinidase DeficiencyClinically supported
An inherited condition in which the body cannot recycle biotin. Lifelong treatment can prevent complications.
- Holocarboxylase Synthetase DeficiencyClinically supported
An inherited condition that stops the body using biotin properly. Immediate treatment and lifelong management with biotin supplements may prevent many complications.
- Multiple Carboxylase DeficiencyClinically supported
The group of disorders, including holocarboxylase synthetase deficiency, in which biotin-dependent enzymes do not work well.
- AlopeciaDeficiency link
Hair loss is a sign of biotin deficiency, but it has many other causes. Biotin helps only when deficiency is the cause.
- DermatitisDeficiency link
Dermatitis can be a sign of biotin deficiency, but it has many other causes.
- GlossitisDeficiency link
A swollen tongue can be a sign of biotin deficiency, but it has many other causes.
- Uncombable Hair SyndromePreliminary or mixed
Three reported cases improved with biotin, but these were case reports only.
Overview
Biotin is vitamin B7. The NHS says it is needed in very small amounts to help the body make fatty acids. Bacteria that live naturally in the bowel can make biotin, and it is found in a wide range of foods but only at very low levels, so it is not clear whether you need any additional biotin from the diet. [1] MedlinePlus says pantothenic acid and biotin help the body break down and use food and are both required for making fatty acids. [2]If you take biotin, tell your doctor and the laboratory before any blood test. The US Food and Drug Administration (FDA) says biotin, often found in dietary supplements, can significantly interfere with certain lab tests and cause incorrect results that may go undetected. [3] This is especially important for heart tests; see below.
Food sources
MedlinePlus lists cereal, chocolate, egg yolk, legumes, milk, nuts, organ meats such as liver and kidney, pork and yeast. [2] The NHS lists no specific foods and says levels in food are very low. [1] See foods high in biotin, thiamin, riboflavin, niacin, B6 and pantothenic acid.Official intake levels
Published levels for the groups named, not personal advice. Biotin has an Adequate Intake (AI) rather than an RDA, used when evidence is not enough to set an RDA. See RDA, AI, DV and UL.| Body, country and year | Group | Level for biotin |
|---|---|---|
| NHS, UK, page reviewed 2020 | Adults | No intake amount given; unclear whether extra is needed [1] |
| US Dietary Reference Intakes, as listed by MedlinePlus (review 2025) | Ages 19 and older (including pregnancy) / lactation | AI 30 mcg / 35 mcg a day [2] |
| Health Canada, table dated 2025 | Adults 19 to 30 | AI 30 mcg a day; no upper level set because data are insufficient [4] |
| EFSA, EU, overview version 2025 | All groups | No adequate data to derive a tolerable upper level [5] |
| NHS, UK, 2020 | Supplement guidance | 0.9 mg or less a day in supplements is unlikely to cause harm [1] |
| Daily Value on US labels (FDA, 2024) | Label reference only | 30 mcg [6] |
Check units: 0.9 mg is 900 mcg, which is 30 times the US AI. Supplement labels commonly use mcg.
Deficiency
Established. MedlinePlus says lack of biotin may lead to muscle pain, dermatitis or glossitis (a swollen tongue), and signs include skin rashes, hair loss and brittle nails. [2] Those signs have many other causes, so they cannot diagnose a deficiency; see a clinician. See vitamin deficiency symptoms.Hair, skin and nails
A 2017 systematic review of case reports and trials found 18 cases of biotin used for hair and nail changes. In every case the person had an underlying condition affecting hair or nail growth, and all improved after biotin. The authors concluded that evidence is limited, that biotin may help in biotin deficiency, brittle nail syndrome or uncombable hair, and that evidence is insufficient for supplementation in healthy people. [7]| Question | What the source found | Label |
|---|---|---|
| Hair or nail changes from biotin deficiency or specific conditions | Improvement in 18 reported cases, from case reports rather than controlled trials. [7] | Promising but limited |
| Hair, skin or nail growth in healthy people | Lack of sufficient evidence for supplementation. [7] | Insufficient evidence |
The review is from 2017. We did not find a newer review we could read in full for this page. See biotin for hair, skin and nails for more.
Biotin and lab-test interference
The FDA page on troponin tests (troponin is a blood test used in heart checks) says the agency has continued to receive adverse event reports indicating that biotin interference caused falsely low troponin results. It also says some test makers have reduced the interference in their assays and others have not. [3] Details of which tests are affected, and how long before a test to pause, are for your clinician or the lab to decide; see biotin and lab-test interference.Practical point: list all supplements, including multivitamins and hair, skin and nail products, whenever blood is drawn. If you have emergency symptoms such as chest pain, call 911 (US) and do not delay care over a supplement question.
Testing
Proper evidence not found in the pages we read for a routine biotin blood test. Do not diagnose deficiency from hair or nail changes. See deficiency testing and its limits.Related
All vitamins · Understanding vitamins · Pantothenic acidFrequently asked questions
Does biotin help hair growth?
A 2017 review found limited research and no sufficient evidence for healthy people; cases that improved had an underlying cause. [7]
Can biotin affect blood test results?
Yes. The FDA says biotin can cause incorrect results in certain lab tests, including falsely low troponin results. [3]
Should I tell my doctor I take biotin?
Yes, along with every other supplement, before blood tests. [3]
What foods contain biotin?
Egg yolk, legumes, nuts, milk, pork, organ meats, cereal and yeast, per MedlinePlus. [2]
Is biotin deficiency common?
Proper evidence not found on how common it is in the pages we read; MedlinePlus lists its signs. [2]
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.
How to read the evidence labels
Labels used on this page: established nutritional role / deficiency treatment, insufficient evidence, no good evidence of benefit (in healthy people), evidence of harm (to test accuracy) and marketing claim. "Proper evidence not found" means we searched the sources named and found nothing usable.
Safety and precautions
- Upper limits: the NHS says there is not enough evidence on high daily doses. [1] MedlinePlus says no toxic symptoms from biotin are known (US). [2] Neither speaks to lab-test effects, which are a separate issue.
- Medicines: Proper evidence not found in the pages we could read (NIH Office of Dietary Supplements pages were blocked). See medication interactions.
- Pregnancy and breastfeeding: the US AI is 30 mcg in pregnancy and 35 mcg in lactation. [2] Ask your care team about any supplement.
- Children, older adults, kidney and liver conditions, surgery: Proper evidence not found specific to biotin. See vitamins for children and teenagers, vitamins and kidney or liver disease and vitamins before surgery.
- Quality: see quality testing and certifications.
References
- NHS (UK). B vitamins and folic acid. Page last reviewed 3 August 2020. Read 2026-10-23.
- MedlinePlus Medical Encyclopedia (US National Library of Medicine). Pantothenic acid and biotin. Review date 1/21/2025. Read 2026-10-23.
- US Food and Drug Administration. Biotin Interference with Troponin Lab Tests - Assays Subject to Biotin Interference. Page dated 06/21/2022. Read 2026-10-23. The FDA safety communication page itself could not be opened; this page summarises it.
- Health Canada. Dietary reference intakes tables: Reference values for vitamins. Page dated 2025-11-19. Read 2026-10-23 through a web-fetch tool, which returned the tables as a text summary; direct download was blocked.
- European Food Safety Authority. Overview on Tolerable Upper Intake Levels as derived by the Scientific Committee on Food (SCF) and the EFSA NDA Panel, version 1, August 2025. Read 2026-10-23 (text extracted from the PDF; table layout reconstructed).
- US Food and Drug Administration. Daily Value on the Nutrition and Supplement Facts Labels. Content current as of 03/05/2024. Read 2026-10-23.
- Patel DP, Swink SM, Castelo-Soccio L. A review of the use of biotin for hair loss. Skin Appendage Disord 2017;3(3):166-169. Read 2026-10-23.