Biotin is the most purchased hair supplement in the US. Brands claim it'll make your hair thicker, longer, and stronger. But what does the research actually say? We review the evidence — and it's more complicated than the marketing suggests.
Why We Reviewed Guide
Biotin (vitamin B7) is essential for keratin production. Deficiency genuinely causes hair loss and brittle nails. The problem: most people aren't deficient, and biotin supplementation only helps if you are.
✅ Pros
- Genuinely helps with biotin deficiency (hair loss)
- Supports nail strength
- Very safe — water soluble, no toxicity risk
- Inexpensive
❌ Cons
- Limited evidence in non-deficient people
- Can interfere with thyroid lab tests (tell your doctor)
- High-dose supplements often unnecessary
Key Ingredients
- Biotin (most products: 5,000–10,000mcg)
- Daily requirement: 30mcg (most get enough from food)
Who Is This For?
Primarily people with confirmed biotin deficiency, those with alopecia, and individuals on restrictive diets. Not necessarily helpful for healthy people with adequate dietary intake.
Check Current Price on Guide
Find well-formulated hair support supplements through our links.
View Best Price →Price & Value
Biotin is very cheap — $10–$15 for 3–6 month supply regardless of brand.
Our Verdict
If you have biotin deficiency, supplementation dramatically helps hair and nails. If you don't, you're likely wasting money. Get tested before supplementing with high doses. We give it a N/A/5 and recommend it for primarily people with confirmed biotin deficiency, those with alopecia, and individuals on restrictive diets. not necessarily helpful for healthy people with adequate dietary intake.