Biotin (Vitamin B7)
Vitamin B7 / H
Ubiquitous in hair/nail pills, but only helps if you're deficient
Evidence tier
No Evidence
Research weight
Not supported
Citations
17 verified / 17
Classification
Vitamin
⊘
What the evidence says. No credible human evidence supports the marketed claims — widely considered ineffective.
⊘
No credible evidence. The claims below are what marketers assert — not what science supports. This entry is included so you can recognise it.
What is Biotin (Vitamin B7)?
Biotin (Vitamin B7) (Vitamin B7 / H) is a vitamin marketed for reverses hair/nail problems caused by genuine deficiency. NutriDex grades the human evidence as No Evidence. Biotin is a water-soluble B vitamin essential for metabolism, and true deficiency can cause hair loss and brittle nails that improve with repletion. However, deficiency is rare, and evidence that supplementation helps hair, skin, or nails in people who are not deficient is essentially absent — the Patel 2017 review found benefit only with an underlying deficiency. Despite this, biotin is near-universal in 'hair, skin, and nails' products, often at hundreds of times the ~30 mcg adequate intake. The most important real-world concern is laboratory interference: high-dose biotin can skew many immunoassays (troponin, thyroid, hormones), and the FDA warns this can cause missed or incorrect diagnoses.
Marketed Claims (unproven)
✕Reverses hair/nail problems caused by genuine deficiency
✕Supports hair/nails in rare deficiency states (claimed)
✕No proven cosmetic benefit at normal biotin levels
Dosing & Compounds
Use & Legality
Adequate intake ~30 mcg/day; megadoses (5–10 mg) sold for hair.
Active Compounds
Safety & Cautions
Direct toxicity is very low (excess is excreted; no upper limit set). The serious, under-recognized risk is lab-test interference: high-dose biotin distorts many immunoassays (troponin, thyroid, hormones), which the FDA warns can cause dangerous misdiagnoses. Stop biotin several days before lab work and tell your clinician you take it. Educational only — always check with your doctor or pharmacist before combining Biotin (Vitamin B7) with any medicine.
Evidence & Risk Findings ★ 17 studies
Systematic review
Yelich 2024
✓ PubMed
Systematic review of biotin for hair loss found only 3 eligible studies; the single double-blind placebo-controlled trial showed no difference between biotin and placebo for hair growth, with benefit only in biotin-deficient or pathology cases.
RCT
Goren 2024 (RCT)
✓ PubMed
In a randomized crossover trial of 10 healthy men, oral biotin 5 mg/day alone did NOT increase hair growth velocity or coverage; only the minoxidil-plus-biotin combination improved hair growth (rate p=0.02; area p<0.01).
RCT
Sesbania/Bambusa biotin RCT 2025
✓ PubMed
Randomized, double-blind, placebo-controlled trial (97 of 105 completing 90 days) found plant-derived biotin, alone or with silica, significantly reduced hair fall versus placebo (both p<0.001) with no adverse events.
RCT
Cureus 2025
✓ Full text
90-day randomized double-blind placebo-controlled trial (105 enrolled, 97 completed) of plant-derived biotin 1.25 mg +/- silica showed increased hair growth rate (~0.55-0.57 mm/day, p<0.0001) and reduced hair fall versus placebo.
RCT
Cree 2020 SPI2 (phase 3 RCT, Lancet Neurology)
✓ PubMed
Landmark phase 3 randomized, double-blind, placebo-controlled trial of high-dose pharmaceutical biotin (MD1003, 300 mg/day) in 642 progressive MS patients found no significant benefit: 12% (39/326) of biotin vs 9% (29/316) of placebo improved on disability/walking at 12 months (OR 1.35, 95% CI 0.81-2.26), and it caused assay interference, so it cannot be recommended.
Agency / regulator
FDA safety communication
✓ Source
High-dose biotin interferes with biotin-streptavidin immunoassays (troponin, TSH, hormones), causing falsely high/low results; the FDA linked one patient death to a falsely low troponin.
guideline
NIH Office of Dietary Supplements – Biotin fact sheet
✓ Source
Authoritative US health-professional fact sheet states biotin deficiency is very rare in well-nourished populations, sets an Adequate Intake of 30 mcg/day for adults, notes no established tolerable upper level or identified toxicity at high doses, and reports that roughly one-third of pregnant women develop marginal deficiency despite adequate intake.
RCT
Tourbah (MS-SPI) 2016
✓ PubMed
Earlier double-blind RCT (n=154) in progressive MS: 12.6% (13/103) of MD1003 high-dose biotin patients achieved confirmed disability reversal at month 9/12 vs 0% on placebo (p=0.005), with reduced EDSS progression; positive signal not replicated in the larger SPI2 trial.
review
Bayart 2023 (review)
✓ PubMed
Review of the biotin-(strept)avidin immunoassay system concludes high-dose biotin supplementation remains a clinically relevant source of false results, requiring assay redesign, depletion, or patient washout to meet FDA tolerance thresholds (~3510 ng/mL).
systematic/scoping review
Nordic Nutrition Recommendations biotin scoping review 2023
✓ Full text
Scoping review for NNR 2023 found symptomatic biotin deficiency is rare and evidence for health benefits or for setting dietary reference values is limited, supporting no role for routine supplementation in healthy adults.
Review
Solvik (Nordic Nutrition Recommendations) 2024
✓ PubMed
Scoping review underpinning Nordic Nutrition Recommendations 2023 concluded symptomatic biotin deficiency is rare, few studies link biotin requirements to health outcomes, and data are insufficient to set firm dietary reference values — supporting adequate-intake (not RDA) guidance only.
Review
Gao 2025
✓ PubMed
Review of cardiac troponin assays documents biotin as a clinically important cause of immunoassay interference (biotin-streptavidin based assays), producing false-negative troponin results that can mask acute myocardial infarction; supports stopping high-dose biotin before testing and mass-spectrometry alternatives.
observational study
Practical Lab Medicine 2025 (study)
✓ PubMed
Study of clinical immunoassays found hemodialysis and ICU patients had elevated biotin causing assay interference; biotin depletion restored accuracy and authors recommend stopping biotin supplements >=72 h before testing.
Review
Patel 2017 (review)
✓ PubMed
Benefit for hair/nails appeared only in patients with an underlying biotin deficiency; insufficient evidence supports supplementation in healthy, non-deficient individuals.
review
Wolf 2016/2023 Biotinidase Deficiency (GeneReviews, NCBI)
✓ Full text
Authoritative gene review establishing biotin as essential lifelong therapy for the inborn error biotinidase deficiency: oral free biotin 5-10 mg/day prevents and can reverse symptoms, and infants identified by newborn screening and treated promptly have normal development, whereas delay risks irreversible hearing loss and optic atrophy.
review
Mock 2005 (review, J Nutr Biochem)
✓ PubMed
Review concludes marginal biotin deficiency arises in about one-third of normal human pregnancies and, while subclinical in women, is demonstrably teratogenic in mice (cleft palate, limb hypoplasia), raising concern that maternal marginal deficiency could be teratogenic in humans.
Case report
Bowen 2019 (case report)
✓ Full text
Patient on 5 mg/day biotin had falsely abnormal TSH, PTH and calcium that normalized within a month of stopping — illustrating the FDA-warned interference.