Benefits of Biotin: What It Does and What the Evidence Shows

Biotin (vitamin B7) is a water-soluble B vitamin your body needs to break down fats, carbohydrates and protein. Adults need about 30 mcg a day, and most people get that from a normal diet, so true deficiency is rare. Biotin is widely sold for hair, skin and nails, but the evidence for those uses in people who are not deficient is weak, and high-dose biotin can make some lab tests, including a key heart test called troponin, read incorrectly.

Evidence grade: Emerging. Biotin's role as an essential nutrient and its Adequate Intake are established NIH reference values, but support for hair, skin and nail benefits in people who are not deficient comes only from case reports and three small nail studies with no placebo group.

What Biotin Does in the Body

Biotin is one of the eight B vitamins. Its main job is to act as a helper (cofactor) for five carboxylase enzymes. These enzymes carry out key steps in metabolizing fatty acids, glucose and amino acids, which is how biotin contributes to normal energy metabolism. Biotin also plays roles in modifying histones (proteins that package DNA), regulating genes and cell signaling.

Free biotin from supplements is absorbed almost completely, even at high doses. Most biotin is stored in the liver. For an overview of how the B vitamins work together, see our guide to B vitamins and the nervous system.

How Much Biotin You Need

There was not enough evidence to set a Recommended Dietary Allowance for biotin, so the Food and Nutrition Board set Adequate Intakes (AIs), based on the amount of biotin in breast milk and adjusted by body weight for other ages.

The Daily Value on supplement labels is also 30 mcg. Many over-the-counter biotin products contain far more; researchers studying lab-test interference describe 10 mg (10,000 mcg) a day as a common supplement dose, which matters for lab testing (see Safety below).

Best Food Sources of Biotin

Organ meats, eggs, fish, meat, seeds, nuts and some vegetables such as sweet potatoes are among the richest sources. Content varies with plant variety, season and processing.

Source: NIH Office of Dietary Supplements. Cook your eggs: raw egg whites contain avidin, a protein that binds biotin and blocks its absorption. Cooking inactivates avidin.

Biotin Deficiency: Rare, but Recognizable

Biotin deficiency is rare, and severe deficiency has never been reported in healthy people eating a normal mixed diet. When it does occur, signs appear gradually and can include thinning hair that can progress to hair loss, a scaly red rash around the eyes, nose and mouth, brittle nails, conjunctivitis and nervous system symptoms such as tingling in the hands and feet, lethargy or low mood.

Groups more likely to have low biotin status include:

• People with biotinidase deficiency, a rare inherited disorder; all U.S. newborns are screened for it.
• People with long-term heavy alcohol use, because alcohol inhibits biotin absorption.
• Pregnant and breastfeeding women: at least a third of pregnant women develop marginal biotin deficiency despite normal intakes, although its significance is not yet clear. Talk to your prenatal care provider about which supplement is right for you.

Biotin for Hair, Skin and Nails: What the Evidence Shows

Because hair loss, rash and brittle nails are signs of deficiency, biotin is heavily marketed for hair, skin and nails. According to the NIH Office of Dietary Supplements, these claims are supported "at best" by a few case reports and small studies.

• Nails: three small studies used 2.5 mg (2,500 mcg) a day for about 5.5 to 15 months in people with brittle nails. One found 91% of 45 people had firmer nails; a retrospective study reported improvement in 63% of 35 people; a third found a 25% increase in nail thickness in 8 people whose nails were measured just before and just after treatment. None had a placebo group, and none reported participants' starting biotin status.
• Hair: evidence is limited to case reports, mostly in children with a rare hair-shaft disorder (uncombable hair syndrome) or other underlying causes. A 2017 review of 18 reported cases found that all of the patients had an underlying cause for poor hair or nail growth and concluded there is not enough evidence to recommend biotin for hair in healthy people.
• Skin: evidence consists of a few case reports, all in infants with rashes.

Bottom line: if your diet is adequate, extra biotin is unlikely to change your hair or nails. Hair thinning has many causes, so it is worth discussing with a clinician rather than self-treating. For general skin nutrition, see antioxidants and skin aging.

Biotin in Supplements

Biotin is available alone, in B-complex supplements and in many multivitamin/mineral products. A multivitamin can help cover small gaps when your diet varies, without the very high amounts found in many hair-focused products.

Safety and Interactions

• No upper limit: the Food and Nutrition Board did not set an upper limit because there is no evidence in humans that biotin is toxic at high intakes. Studies have found no adverse effects at 10-50 mg a day.
• Lab test interference (FDA warning): many lab tests use biotin-streptavidin technology. The FDA warns that biotin in dietary supplements can significantly interfere with certain tests and cause incorrect results that may go undetected. In a study of six healthy adults taking 10 mg a day for one week, 9 of 23 biotin-based tests gave falsely high or falsely low results. Affected tests can include thyroid hormones, vitamin D and troponin, a test used to help diagnose a heart attack. The FDA has received reports of falsely low troponin results, and according to the FDA one patient taking high-dose biotin died after a troponin test gave a falsely low result. Even a single 10 mg dose has affected thyroid tests taken within 24 hours.
• What to do: tell your clinician and the lab about every supplement you take that contains biotin, including multivitamins and hair, skin and nail products, and ask whether you should pause it before blood work.
• Anticonvulsant medicines: long-term use of carbamazepine, primidone, phenytoin or phenobarbital is associated with lower biotin levels. If you take one of these, talk to your doctor or pharmacist about your biotin status.
• Pregnancy and breastfeeding: needs are slightly higher; talk to your healthcare provider before adding any supplement.

Frequently Asked Questions

What are the main benefits of biotin?

Biotin is essential for normal metabolism of fats, carbohydrates and protein. Getting enough prevents deficiency, whose signs include hair thinning, a scaly rash and brittle nails. Benefits beyond meeting your needs are not well established.

Does biotin help hair growth?

Only weak evidence supports it, mostly case reports in people with deficiency or rare hair disorders. A 2017 review found insufficient evidence for biotin supplements in healthy people.

How much biotin should I take per day?

Adults need about 30 mcg a day (35 mcg when breastfeeding), which most diets provide. There is no set upper limit, but high doses can interfere with lab tests.

Can biotin affect blood test results?

Yes. The FDA warns that biotin can cause falsely high or low results on some lab tests, including thyroid and troponin tests. Tell your clinician and the lab if you take biotin.

Which foods are highest in biotin?

Beef liver (30.8 mcg per 3 ounces) and cooked eggs (10 mcg each) are top sources, followed by salmon, pork, beef, sunflower seeds, sweet potatoes and almonds.

Is biotin deficiency common?

No. It is rare in healthy people eating a mixed diet. Risk is higher with biotinidase deficiency, long-term heavy alcohol use and pregnancy.

Sources

1. NIH Office of Dietary Supplements. Biotin: Fact Sheet for Health Professionals. Updated 2022.
2. U.S. Food and Drug Administration. Biotin Interference with Troponin Lab Tests - Assays Subject to Biotin Interference. Content current as of 2022.
3. Li D, Radulescu A, Shrestha RT, et al. Association of Biotin Ingestion With Performance of Hormone and Nonhormone Assays in Healthy Adults. JAMA. 2017.
4. Patel DP, Swink SM, Castelo-Soccio L. A Review of the Use of Biotin for Hair Loss. Skin Appendage Disord. 2017.
5. NIH Office of Dietary Supplements. Biotin: Fact Sheet for Consumers.

Disclosure: OPA Nutrition sells supplements, including products mentioned in this article. This content is for education only and is not medical advice. Statements about dietary supplements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease. Talk to your healthcare provider before using any supplement, especially if you take medication or have a medical condition.

Written and reviewed by Michael Gonzales, Founder, OPA Nutrition · Last reviewed: October 17, 2026 · How OPA researches and writes