Biotin (Vitamin B7)
Biotin
TL;DR
Biotin is a B vitamin essential for fat and carbohydrate metabolism. Deficiency is rare, hair and nail benefits are largely unproven, and it distorts lab tests.
Ideal For
- People with diagnosed biotin deficiency
- Those on long-term anticonvulsant therapy
- People with brittle nail syndrome
- Adults with malabsorption or after bariatric surgery
Avoid If
- You have blood tests scheduled within 72 hours
- You are being monitored for thyroid or cardiac markers
- You expect hair regrowth without an underlying deficiency
Frequently Asked Questions
Overview
Biotin, vitamin B7, is the cofactor for five carboxylase enzymes involved in fatty acid synthesis, gluconeogenesis and amino acid catabolism. Requirements are small — adequate intake is 30 micrograms a day — and gut bacteria contribute some of it. Deficiency is genuinely rare, appearing mainly in biotinidase deficiency, long-term anticonvulsant use, chronic alcohol use, and in people who eat large amounts of raw egg white, which contains avidin that binds biotin.
The gap between reputation and evidence is wide. Biotin is marketed heavily for hair, skin and nails, but the supporting studies are small, old, and almost all conducted in people with an underlying deficiency or a nail disorder. In people with normal biotin status, there is no good evidence that supplementation thickens hair or strengthens nails. A 2017 review of the literature found no randomised controlled trials supporting biotin for hair growth in healthy people.
There is one genuinely important practical issue. Doses commonly sold — 5,000 to 10,000 micrograms — interfere with immunoassays that use biotin-streptavidin binding, distorting troponin, thyroid and hormone results. The FDA has issued warnings after a death linked to a falsely low troponin. Stop biotin at least 72 hours before blood work.
How It Works
- Cofactor for acetyl-CoA carboxylase in fatty acid synthesis
- Required for pyruvate carboxylase in gluconeogenesis
- Cofactor for propionyl-CoA and methylcrotonyl-CoA carboxylases in amino acid catabolism
- Involved in histone biotinylation and gene regulation
- Supports keratin infrastructure, the basis of the hair and nail claims
Quick Facts
- Essential for metabolism of macronutrients
- Supports healthy hair growth and strength
- Promotes nail health and reduces brittleness
- Important for skin health
- Generally adequate in diet but deficiency possible
Benefits & Outcomes
Wrinkle Reduction
Biotin does nothing for wrinkles and interferes with laboratory tests.
Hair Growth
Biotin supports hair growth only when a true deficiency exists; for the vast majority of people, supplementation does not accelerate growth.
Scalp Health
Biotin only helps the rare person who is actually deficient, and it wrecks common lab tests.
Skin Elasticity
Biotin has no evidence for skin elasticity in people who are not deficient.
Nail Strength
A classic trial showed 2.5 mg/day increased nail thickness 25% in brittle-nail patients; no good evidence for people with healthy nails.
Skin Health Enhancement
Biotin for skin and nails is popular but supported almost entirely by deficiency case series, not controlled trials.
Hair Follicle Stimulation
Only works in genuine deficiency, which is rare.
Metabolic Optimization
High-dose biotin has been trialled for glucose metabolism and multiple sclerosis with disappointing results.
Increased Energy Production
Biotin is a metabolic cofactor, but supplementing it does not increase energy in people who are not deficient.
Health Concerns Addressed
Premature Gray Hair
Biotin is heavily marketed against gray hair, but no trial has ever shown it prevents or reverses graying — the honest move is testing B12 and thyroid if graying is rapid, not buying biotin.
Slow Hair Growth
Biotin only helps slow hair growth when a true deficiency exists — which is rare — and supplements can distort important blood tests.
Multiple Sclerosis
Do not use. The definitive trial was negative, and the assay interference creates real clinical risk.
Hair Thinning & Loss
Biotin only helps hair loss when there is a genuine biotin deficiency, which is rare - and high doses dangerously distort lab tests.
Supporting Research15 studies
A Review of the Use of Biotin for Hair Loss
Patel DP, Swink SM, Castelo-Soccio L
All reported cases of clinical improvement with biotin occurred in patients with an underlying biotin deficiency or inherited metabolic disorder; there is no evidence of benefit in healthy individuals.
Safety and efficacy of MD1003 (high-dose biotin) in patients with progressive multiple sclerosis (SPI2): a randomised, double-blind, placebo-controlled, phase 3 trial
Cree BAC, et al
This study showed that MD1003 did not significantly improve disability or walking speed in patients with progressive multiple sclerosis.
The role of biotin in hair and nail disorders: a systematic review
Patel DP, Swink SM, Castelo-Soccio L
Every case of clinical benefit occurred in patients with an underlying biotin deficiency; no evidence supported use in healthy people
Treatment of brittle nail with a hydroxypropyl chitosan-based lacquer, alone or in combination with oral biotin: A randomized, assessor-blinded trial
Chiavetta A, Mazzurco S, Secolo MP +2 more
Twenty-six were randomly assigned to HPC-NL and 24 to the HPC-NL and biotin, 10 mg/daily (+B).
Premature graying of hair: Risk factors, co-morbid conditions, pharmacotherapy and reversal - A systematic review and meta-analysis
Mahendiratta S
Vitamin deficiency (B12, folic acid, and B7) is found to be associated with PGH.
Infantile flexural seborrhoeic dermatitis. Neither biotin nor essential fatty acid deficiency
Erlichman M
No beneficial effect could be confirmed, and it is therefore unlikely that this disease is caused by biotin deficiency.
The Role of Vitamins and Minerals in Hair Loss: A Review
Almohanna HM, Ahmed AA, Tsatalis JP +1 more
The role of nutrition and diet in treating hair loss represents a dynamic and growing area of inquiry.
Biotin for the treatment of nail disease: what is the evidence?
Lipner SR, Scher RK
Evidence for biotin in brittle nail syndrome rests on three small uncontrolled studies; no randomized controlled trials support its use.
Vitamins and minerals: their role in nail health and disease
Scheinfeld N, Dahdah MJ, Scher R
Brittle nail syndrome appears to abate with supplementation with a 2.5-mg dose of biotin daily or a 10-mg dose of silicon daily.
Biotin Interference in Immunoassays and Patient Safety
Dasgupta A, Yeo KJ
High-dose biotin supplementation can cause falsely high or falsely low results in biotin-streptavidin immunoassays, including thyroid and troponin tests, with documented patient harm.
Risks of Skin, Hair, and Nail Supplements
Burns EK, Perez-Sanchez A, Katta R
Interactions with drugs and laboratory testing have been documented in research studies.
Best practices in mitigating the risk of biotin interference with laboratory testing
Bowen R, Benavides R, Colon-Franco JM +1 more
Dietary biotin intake rarely reaches interference thresholds, but supplements of 5 mg or more can produce clinically significant assay interference.
Treatment of brittle fingernails and onychoschizia with biotin: scanning electron microscopy
Colombo VE, Gerber F, Bronhofer M +1 more
The thickness of the nails in group B increased significantly by 25%.
Pathogenesis, Clinical Signs and Treatment Recommendations in Brittle Nails: A Review
Chessa MA, Iorizzo M, Richert B +1 more
In idiopathic NF oral supplementation, vitamins (especially biotin, also known as vitamin B7), trace elements and amino acids (especially cysteine) have been reported to be useful.
Interventions for alopecia areata
Delamere FM, Sladden MJ, Dobbins HM +1 more
No intervention studied showed significant benefit on long-term hair growth in alopecia areata compared with placebo.
Safety Information
Potential Side Effects
No established toxicity even at high doses; excess is excreted in urine. The real harm from biotin comes from misleading laboratory results rather than direct effects. Occasional acne reports at high doses.
Contraindications
No toxicity concerns, but high doses must be stopped before laboratory testing because of immunoassay interference affecting troponin, TSH, free T4 and hormone panels.
Drug Interactions
- Anticonvulsants including carbamazepine, phenytoin and phenobarbital — these deplete biotin
- Laboratory immunoassays — high-dose biotin causes falsely high or low results depending on assay design
- Chronic alcohol use — impairs biotin absorption
Pregnancy & Breastfeeding
Pregnancy: safe
Breastfeeding: safe
Dosage Guidelines
Dosage Used in Studies
30-10000 mcg
Best Time to Take
Morning with breakfast
Best Form
D-biotin at a modest dose, ideally within a B-complex rather than as a mega-dose standalone
Bioavailability
Well absorbed in small intestine. Water-soluble vitamin. Higher doses (5-10mg) used for hair/nail health lack strong evidence but appear safe. May interfere with lab tests.
Forms Compared
D-biotin
Biotin in B-complex
High-dose standalone biotin
Food & Timing
With or without food
Medical Disclaimer
The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.
Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.