BiotinBiotin provides a high amount of biotin (also sometimes called vitamin B7) per capsule. Biotin's benefit for fingernail strength was demonstrated in a clinical trial, where 45 patients with brittle nails received oral supplementation of 2. 5 mg biotin for 1. 5 7 months. Ninety one percent showed "definite improvement," exhibiting firmer, harder fingernails after an average of two months of supplementation.* Biotin also supports healthy skin, hair, and