Biotin
A B vitamin popular for hair and nails, though it mainly helps when you're deficient.
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What it is
Biotin is a B vitamin involved in metabolizing fats, carbs, and protein. It's widely marketed for hair, skin, and nails, but true deficiency is uncommon since it's found in many foods and made by gut bacteria.
How it works
Biotin (vitamin B7) is a coenzyme for enzymes that metabolize fats, carbohydrates, and protein. It's genuinely essential, but it's widespread in food and even made by gut bacteria, so true deficiency is rare. Its popularity for hair, skin, and nails rests largely on the fact that deficiency causes hair and nail problems — which is different from proving benefit in people who aren't deficient.
What it's been studied for
Taken to support hair and nail strength, mostly relevant when intake is genuinely low.
What the evidence shows
Evidence for hair and nail benefits in people who aren't deficient is weak. Biotin reliably helps only when there's an actual deficiency, which is rare.
Who should consider it
It mainly benefits people with an actual biotin deficiency, which is uncommon (seen with certain genetic conditions, long-term raw-egg-white consumption, or some medications). Despite heavy marketing for hair and nails, most people with adequate biotin won't notice a difference. It's often chosen by people troubled by hair thinning or brittle nails.
Amounts commonly studied
Supplements often contain far more than needed (5,000-10,000 mcg); the daily requirement is only about 30 mcg.
How to take it
Supplements often contain far more than needed — 5,000-10,000 mcg — versus a daily requirement of only about 30 mcg. It can be taken any time, with or without food. Importantly, stop it before scheduled bloodwork if your provider advises, because high biotin can distort lab results.
Forms & absorption
Sold alone or in hair/skin/nail formulas and B-complexes.
Food sources
Found in eggs (especially the yolk), nuts and seeds, salmon, pork, sweet potatoes, and whole grains. Because it's so widespread and made by gut bacteria, most people get plenty.
Safety & interactions
Very safe, but important: high-dose biotin can significantly interfere with lab tests, including thyroid and cardiac (troponin) tests, causing false results. Tell your provider if you take it, and stop before bloodwork if advised.
Myths & what it won't do
Myth: biotin reliably grows hair and strengthens nails. Reality: it mainly helps if you're deficient — which is uncommon — and evidence in non-deficient people is weak. Myth: high-dose biotin is harmless. Reality: it's safe in the body, but it can significantly interfere with lab tests, including thyroid and cardiac (troponin) tests, causing false results.
Common questions
- Will biotin actually help my hair?
- Only if you're deficient, which is uncommon. In people with normal biotin levels, the hair and nail benefits are largely unproven.
- Why does it affect blood tests?
- High-dose biotin can interfere with the lab methods used for thyroid, hormone, and heart (troponin) tests, causing falsely high or low results. Tell your provider you take it.
- How much is too much?
- There's no established toxicity, but there's little reason to take mega-doses, and higher amounts increase the lab-interference risk. Stopping before bloodwork is wise.
The amounts listed here are what published research has used — not a prescription or a recommended dose for you. Confirm anything you plan to take with your own healthcare provider, especially if you take medications, are pregnant or nursing, or have a health condition.
Related goals
Research on Biotin
Recommendations on this page are informed by published research. This is educational information, not medical advice.
- Patel DP, Swink SM, Castelo-Soccio L. A Review of the Use of Biotin for Hair Loss. Skin Appendage Disord. 2017;3(3):166-169. View study →Note: Every reported benefit came from people with an underlying cause of poor hair or nail growth; the authors found insufficient evidence for supplementing healthy people.