Biotin
Biotin (Vitamin B7)
The most-marketed hair vitamin — but it only helps if you're deficient, which almost no one is.
How Biotin works — and how well we know it
Biotin is a coenzyme for carboxylase enzymes involved in fatty acid synthesis and amino acid metabolism. Severe deficiency causes hair loss alongside dermatitis and neurological symptoms — but true deficiency is extremely rare in healthy adults eating a normal diet.
oral
RDA 30 mcg/day. Supplement marketing typically uses 1,000–10,000 mcg.
Available as a dietary supplement. RDA is 30 mcg/day. Marketed supplement doses range from 1,000 to 10,000 mcg — 30–330× the RDA.
People with documented biotin deficiency (rare). Otherwise, no expected hair-loss benefit.
Evidence distribution across 2 claims
Why the grade is D. Helps hair growth only in the rare case of true deficiency. No RCT evidence supports supplementation in non-deficient adults. Mega-doses can interfere with thyroid and cardiac lab tests.
Every claim, traced back to its source
We took every major claim made about Biotin and matched it to the specific experimental model behind it. Click a claim to see the model, the finding, and our assessment of how much weight it deserves.
2 claims · evidence-by-evidence breakdown
1Open-LabelWeight: ModerateBiotin supplementation reverses hair loss in confirmed deficiencyBiotin reverses hair loss caused by biotin deficiency. True deficiency is rare; supplementing the rest of us isn't supported.
Case reports and small series of patients with documented biotin deficiency (typically from biotinidase deficiency, prolonged IV nutrition, or specific dietary patterns), treated with biotin supplementation.
Patients with true deficiency consistently show resolution of hair loss with supplementation.
The deficiency story is real — biotin is a true cofactor and severe deficiency produces alopecia. But this finding does not extrapolate to non-deficient adults. The hair-supplement industry uses these case reports to justify mega-dose supplementation in the general population.
- Patel DP, Swink SM, Castelo-Soccio L (2017). Skin Appendage Disord PMID 28879195
2Open-LabelWeight: HighMega-dose biotin distorts immunoassay lab testsMega-dose biotin causes false-positive and false-negative results on common blood tests — a real clinical risk.
FDA safety communications, case reports, and analytical chemistry studies documenting interference of high-dose biotin with biotin-streptavidin-based immunoassays.
Biotin doses above 1,000 mcg can cause false-low or false-high readings on thyroid function tests (TSH, T4), troponin (cardiac), parathyroid hormone, and other immunoassays. At 5,000 mcg, interference is documented and clinically significant.
This is a real harm, not a hypothetical. The FDA issued a safety communication. Patients taking high-dose biotin have been misdiagnosed with thyroid disease and missed cardiac events because their labs were artificially shifted.
- FDA Safety Communication (2019). FDA
What's still missing from the science
- Any placebo-controlled RCT of biotin supplementation for AGA in non-deficient adults.
- Dose-response data — is there any dose at which biotin helps non-deficient people?
Our verdict on Biotin
Not in our formulary yet
We don't carry this ingredient. We only formulate around actives where the evidence — and the safety profile — is strong enough to recommend with confidence. As the data matures, we may revisit.
Related treatments
How does Biotin stack up against its closest peers?
A genuine cause of reversible hair shedding in iron-deficient patients — but useless and potentially harmful if your iron stores are normal.
Read the breakdown →A botanical 5-alpha reductase inhibitor whose only high-quality trials (in BPH) showed no benefit over placebo; the positive AGA data are small and low-quality.
Read the breakdown →One small Malaysian RCT showed a hair-count increase. Never replicated. Used by Nutrafol to justify its tocotrienol content.
Read the breakdown →