Biotin
Vitamin B7 / vitamin H · Foundation
A hair-and-nails staple that helps almost nobody — and can make your blood tests lie.
What the evidence says
Biotin deficiency causes hair loss, and correcting it reverses that. Deficiency is rare. In people who are not deficient — which is nearly everyone taking it — there is essentially no controlled evidence that high-dose biotin grows hair or strengthens nails, and the case reports supporting it involve people with genuine deficiency states.
What studies used
Adequate intake is about 30 mcg/day; common 5,000–10,000 mcg retail products supply roughly 170–330 times that. Published studies had not established a preferred timing.
Reported from published studies and product labelling — a record of what was used in research, not a recommendation. What is right for you is a conversation with a clinician.
Watch out for
- THE important one: high-dose biotin interferes with many immunoassays and can produce falsely LOW troponin results — the FDA has warned this contributed to a missed heart attack, and it also skews thyroid panels. Laboratory interference required disclosure to whoever ordered the test; assay-specific handling varied
Evidence base
established literature
Strong human evidence: either a phase 3 or 4 trial report alongside review-level evidence, or ten or more randomised controlled trial reports.
This letter measures how much human research exists, not whether it works for you — the tier above (Limited) is the read on quality.
Research (12)
- The Role of Vitamins and Minerals in Hair Loss: A ReviewDermatol Ther (Heidelb) · 2019
- Biotin: From Nutrition to TherapeuticsJ Nutr · 2017
- A Review of the Use of Biotin for Hair LossSkin Appendage Disord · 2017
- Hormone Immunoassay Interference: A 2021 UpdateAnn Lab Med · 2022
- Hair, Nails, and Skin: Differentiating Cutaneous Manifestations of Micronutrient DeficiencyNutr Clin Pract · 2019
- Immunoassay design and biotin interferenceAdv Clin Chem · 2022
- Addressing the Root Causes of Female Hair Loss and Non-Pharmaceutical InterventionsJ Drugs Dermatol · 2025
- Biotinidase Deficiency1993
- Biotin Deficiency2026
- Biotin deficiencyLancet · 1981
- BiotinVitam Horm · 1989
- Biotinidase Deficiency2026
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