Biotin for Hair, Skin, and Nails: Separating Fact from Fiction

Biotin (vitamin B7) has become synonymous with beauty supplements, with countless products promising thicker hair, clearer skin, and stronger nails. But does the science support these claims?

Biotin is a water-soluble B vitamin that acts as a cofactor for enzymes involved in fatty acid synthesis, amino acid metabolism, and glucose production. Biotin contributes to the maintenance of normal hair and skin.

For people with adequate biotin levels, the evidence is less clear. A 2017 review in the journal Skin Appendage Disorders found that in all published cases of biotin supplementation improving hair or nails, the subjects either had a pathological condition or an underlying deficiency.

Biotin has slightly stronger evidence for nail health.

However, there is limited evidence that supplementation improves skin quality in people who are not deficient.

If you take medication, ask your pharmacist before taking biotin.

Zinc contributes to the maintenance of normal hair, skin and nails; vitamin C contributes to normal collagen formation for the normal function of skin.

Biotin supplements are widely available, but quality and dosing vary significantly:

• D-Biotin: This is the naturally occurring, biologically active form. It should be listed as "D-Biotin" or simply "Biotin" on the label. Avoid products that do not specify the form.
• Dosage considerations: The UK NRV for biotin is just 50 mcg, but supplements often contain 1,000–10,000 mcg. Higher is not necessarily better — choose a dose appropriate for your goals.
• Some formulas add zinc and selenium, which contribute to the maintenance of normal hair and nails.
• Lab testing warning: High-dose biotin can interfere with certain blood tests, including thyroid function tests and troponin (a cardiac marker). If you take biotin and need blood work, inform your doctor and stop supplementation 48–72 hours before the test.

Biotin supplementation may be particularly beneficial for:

• If you notice unexplained hair loss, see your GP.
• People with diagnosed biotin deficiency (though true deficiency is rare)
• People who consume raw egg whites regularly (avidin in raw egg whites binds biotin and prevents absorption)
• Biotin contributes to the maintenance of normal hair.

Take biotin with a meal for best absorption. Support biotin from within by eating biotin-rich foods: eggs (cooked, not raw), almonds, sweet potatoes, spinach, and broccoli. Avoid excessive alcohol consumption, which impairs biotin absorption. Manage expectations: biotin is most effective for people who are actually deficient.