Biotin (vitamin B7) · supplement
Evidence tier: insufficient
A B-vitamin essential for keratin synthesis, supports hair, nails, and skin when deficient or marginally low.
Biotin is a water soluble B vitamin that acts as a cofactor for five carboxylase enzymes involved in fatty acid synthesis, amino acid breakdown and gluconeogenesis. That biochemistry is settled. What is NOT established is the step the marketing depends on: that adding biotin above the level a normal diet already supplies increases keratin production or hair and nail growth in a person whose carboxylases are already fully saturated. The lab test interference has its own mechanism and it is entirely separate from the vitamin biology: many clinical immunoassays are built on the biotin and streptavidin binding system, so an excess of circulating biotin from a supplement competes with the assay's own biotin reagent and distorts the reading.
Two different verdicts that must be kept apart. For CORRECTING a genuine, diagnosed biotin deficiency, biotin works, and that is not in dispute: deficiency causes hair thinning, brittle nails and rash, and repletion resolves them. But biotin deficiency is rare, and almost nobody buying a biotin supplement has it. For the reason biotin is actually sold, thicker hair and stronger nails in people who are NOT deficient, the evidence is essentially non existent. NIH ODS states that the hair, skin and nail claims 'are supported, at best, by only a few case reports and small studies', and that 'in the absence of additional studies, there is no evidence to suggest benefit from biotin supplementation outside of known deficiencies secondary to congenital or acquired causes.' The dedicated review is even blunter: Patel, Swink and Castelo Soccio, Skin Appendage Disorders 2017 (PMID 28879195), searched the literature for every reported case of biotin used for hair or nail growth, found 18, and in EVERY ONE the patient had an underlying pathology causing the poor growth. There are no randomised controlled trials showing benefit in healthy people. The Adequate Intake is 30 mcg per day and is met by ordinary diet; hair and nail supplements typically deliver 1,000 to 10,000 mcg, which is 33 to 333 times that. Here is the part that matters more than the efficacy question, because on biotin the efficacy and the safety point in OPPOSITE directions. Biotin is not toxic, but at supplement doses it CORRUPTS LABORATORY BLOOD TESTS. The FDA issued a safety communication in 2017 and reissued it in November 2019 warning that biotin interferes with immunoassays and can produce falsely LOW troponin results. Troponin is the blood test used to diagnose a heart attack. The FDA has stated that it received a report of a patient taking high dose biotin who DIED following a falsely low troponin result. Biotin also skews thyroid panels, producing a pattern that mimics Graves disease and has led to misdiagnosis. The honest headline for biotin is not 'it probably will not help your hair'. It is 'it probably will not help your hair, and it can hide your heart attack'.
The Adequate Intake set by the NIH is 30 mcg per day for adults, and ordinary diet meets it. No effective supplemental dose for hair or nails has ever been established, because no benefit has been established. Marketed hair and nail products commonly contain 1,000 to 10,000 mcg. If biotin is being taken at supplement doses, it should be stopped well before any blood test, and the testing laboratory should be told.
1000 to 5000 mcg daily. With food.
Very safe. Can interfere with thyroid lab tests, pause for 48 hours before testing.
Pregnancy: caution
Breastfeeding: caution
Active compounds: biotin (vitamin B7)
Remedies using Biotin · Browse by body system · Check it against what you take
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.