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Not medical advice. This article is general information, not a substitute for advice from your doctor or pharmacist. Check with them before starting supplements, especially if you are pregnant, nursing, or take prescription medication (for example blood thinners, thyroid medication, or antibiotics).
Biotin is one of the best-selling “beauty vitamins” on the market. Gummies, capsules, and shampoos promise thicker hair, stronger nails, and clearer skin. The research behind those promises is a lot thinner than the marketing, and there’s one real risk most labels barely mention.
Quick facts
| What it is | Vitamin B7, a water-soluble B vitamin that helps your body use fats, carbohydrates, and protein |
| How much you need | 30 mcg a day for adults (35 mcg while breastfeeding) |
| How much supplements contain | Often thousands of mcg per serving, many times the daily need |
| Upper limit | None set; no evidence of toxicity at high intakes |
| Evidence for hair, skin, nails | Weak in people who are not deficient |
| The real risk | High doses can cause false results on important lab tests |
What biotin actually does
Biotin helps enzymes break down the food you eat into energy. It is also involved in making keratin, the protein in hair and nails, which is where the beauty claims come from. True biotin deficiency can cause thinning hair, brittle nails, and a scaly red rash around the eyes, nose, and mouth, but deficiency is rare in people who eat a normal diet. Eggs, meat, fish, seeds, nuts, and some vegetables all contain it.
Does it work for hair, skin and nails?
For people who aren’t deficient, the evidence is limited. The NIH Office of Dietary Supplements puts it plainly: the claims are “supported, at best, by only a few case reports and small studies.”
- Nails: The most promising evidence. Three small trials without control groups found that 2.5 mg a day improved brittle nails in many participants. Without a placebo group, it’s hard to know how much of that was the biotin.
- Hair: Evidence consists mostly of case reports, often in people with an underlying deficiency or medical condition. There’s no good evidence it thickens hair in healthy adults.
- Skin: Mainly case reports. The rash from deficiency improves with biotin; there’s no evidence it improves normal skin.
If you’re losing hair, the cause is more often something else, such as genetics, stress, thyroid issues, low iron, or hormonal changes. That’s worth a conversation with a doctor rather than a bottle of gummies.
The lab test problem
This is the part that matters most. Many common blood tests use a biotin-based process, and high amounts of biotin in your blood can throw off the results. The FDA has warned about this, and the NIH reports the case of a patient taking high-dose biotin who died after a heart attack test (troponin) came back falsely low. Even a single 10 mg dose can interfere with thyroid tests within 24 hours, potentially making it look like you have an overactive thyroid.
If you take biotin, tell your doctor before any blood work, and ask whether you should pause it beforehand. This applies to hair, skin, and nail blends and some multivitamins too, so check the label.
Who should consider it
- People with a diagnosed biotin deficiency.
- People with brittle nails who want to try it, knowing the evidence is modest, and who will tell their doctor they take it.
Who can probably skip it
- Healthy adults eating a varied diet who want thicker hair or clearer skin.
- Anyone with upcoming lab work or heart or thyroid monitoring, unless their doctor agrees.
Our take
Biotin is safe in the sense that it isn’t toxic, but for most people it’s a low-value purchase for hair and skin, and the lab test risk is real. If you want better skin, topical products with stronger evidence, like a retinoid, vitamin C serum, and daily sunscreen, are a better use of money. See Best Vitamins for Skin for what the evidence supports, and our vitamin interaction chart before combining supplements.