Biotin

Educational overview

Dietary supplement; high doses can produce dangerously misleading thyroid, cardiac, and other laboratory results.

Biotin (vitamin B7, formerly vitamin H) is a water-soluble B vitamin that functions as a covalently bound cofactor for five carboxylase enzymes involved in fatty acid synthesis, gluconeogenesis, and the catabolism of branched-chain amino acids. It occurs in egg yolk, liver, salmon, nuts, and seeds, and gut bacteria synthesize some as well. Because the Food and Nutrition Board found insufficient data to set an RDA, only an Adequate Intake is published for biotin, and no tolerable upper intake level has been established. Frank deficiency is rare and is seen mainly in inherited biotinidase deficiency, prolonged parenteral nutrition without biotin, long-term anticonvulsant therapy, and habitual consumption of raw egg white, which contains the biotin-binding protein avidin.

Human evidence for supplementation in people without deficiency is thin. The widespread marketing of biotin for hair, skin, and nail health rests largely on case reports of children with rare hair-shaft disorders and on small uncontrolled series in brittle nails; a 2017 review in Skin Appendage Disorders found no randomized trials supporting benefit in healthy individuals. Pharmacologic high-dose biotin (MD1003) was tested for progressive multiple sclerosis after an encouraging pilot study, but the phase 3 SPI2 trial published in Lancet Neurology in 2020 found no effect on disability. The most robust human data concern an unintended effect: a 2017 JAMA study demonstrated that ordinary supplement amounts can distort clinical laboratory results.

In the United States, biotin is sold as a dietary supplement and as a component of multivitamins and prenatal products; it is not an FDA-approved drug for any indication, though it is an ingredient of FDA-approved parenteral multivitamins. No stand-alone injectable biotin product is FDA-approved; injectable hair-growth formulations come from compounding pharmacies or unregulated sellers. FDA issued safety communications in 2017 and 2019 warning that biotin in blood samples can interfere with immunoassays that use biotin-streptavidin technology, producing falsely high or falsely low results, and it has singled out falsely low troponin as a particular concern. In the European Union, biotin is a permitted food supplement ingredient with authorized health claims limited to normal physiological functions.

Biotin tablets, capsules, and gummies are stable at room temperature when protected from moisture and light, with expiry dates set by the manufacturer. For a dose log or inventory record, the most consequential detail is the amount per serving, because assay interference scales with exposure and can persist for days after high-dose products are stopped. Recording the last date and time of intake before any blood draw allows a laboratory or clinician to interpret results such as thyroid function tests, troponin, vitamin D, and hormone panels appropriately. Multi-ingredient hair, skin, and nail products frequently contain far more biotin than the Adequate Intake, so the label amount rather than the product name is the relevant entry.

Category

Vitamin

Routes represented

Oral

Storage context

Follow the product label; store in the original container away from excess heat and moisture.