Compound or practice · Supplement
Biotin (B7)
The hair-and-nails vitamin that only helps if you're deficient — and wrecks common lab tests at high doses.
- Overall grade
- Grade C
- Last revised
- 2
- graded outcomes
- 0
- references listed
A structured monograph in Prometheus's bundled library. Its grades are the monograph's own reading of the evidence, not a peer-reviewed review.
1 at grade B · 1 at grade D — 2 graded rows
What is known
Each outcome with its grade (how strong the evidence is, A to D), the size of the effect where the entry records one, and how often studies agree.
- Deficiency-related hair lossEvidence grade B
Reverses it
Moderatehigh
- Hair/nails (non-deficient)Evidence grade D
Only helps if deficient
Trivialmixed
What is uncertain
Read off the same rows as above. Nothing here is added that the entry does not itself record.
- Thin evidence: Hair/nails (non-deficient) (grade D).
The evidence in words
What it is
Biotin (vitamin B7) is a coenzyme in fatty-acid and glucose metabolism, marketed heavily for hair, skin, and nails.
How it works
It is a cofactor for carboxylase enzymes; hair/nail benefits appear only when biotin is genuinely lacking.
What the evidence shows
Deficiency (rare) causes hair loss that biotin reverses; in people who aren't deficient, evidence for hair/nail improvement is weak. Critically, high-dose biotin interferes with many immunoassays (thyroid, troponin), causing dangerous false lab results.
How to use it
Only needed for deficiency; stop biotin several days before blood tests.
Safety & interactions
Safe, but the lab-test interference is a real clinical hazard — disclose supplementation before testing.
Bottom line
Skip it for hair unless you're deficient — and always tell the lab, because high-dose biotin falsifies thyroid and cardiac tests.
How it is used
As the entry records it, from the studies it summarises. Not a recommendation for you — doses that suit a trial population may not suit you.
- Deficiency only
- Per clinician; stop before blood tests.
Related reading
Entries that share this one's tags or conditions.
- Biotin (B7) for Deficiency-related hair lossEvidence grade B — Reverses itEvidence grade B
- Biotin (B7) for Hair/nails (non-deficient)Evidence grade D — Only helps if deficientEvidence grade D
- Biotin (B7): dosage and how to take itPer clinician; stop before blood tests.Evidence grade C
- Biotin (B7): side effects, safety & interactionsSafe, but the lab-test interference is a real clinical hazard — disclose supplementation before testing.Evidence grade C
Sources
This entry lists no references of its own.
Last revised . A grade is this entry's reading of the evidence, not medical advice.