Short answer: biotin helps hair growth mainly in people who have an actual biotin deficiency. For most people with normal biotin levels, taking more biotin alone shows limited additional benefit.
What biotin actually does
Biotin (vitamin B7) supports keratin production, the structural protein hair is made from. If you are deficient, which is uncommon but does happen with restrictive diets, certain medications or pregnancy, supplementing can measurably improve hair and nail strength.
Who is actually biotin deficient
People on long-term anticonvulsant medication, heavy alcohol users, pregnant and breastfeeding women, and people eating large amounts of raw egg whites.
Should you still take it
Yes, as part of a broader formula. Biotin is inexpensive and generally safe at supplement doses, but it should not be the only active ingredient in a hair supplement you are relying on.
One caution: high-dose biotin can interfere with certain lab tests, notably thyroid panels. Tell your doctor you are taking biotin before any blood test.