Biotin is a water-soluble vitamin, generally classified as a member of the B complex family but sometimes called "vitamin H" for the words Haar and Haut, which mean "hair and skin" in German.

Biotin serves as an essential coenzyme for five biotin-dependent carboxylase reactions that participate in numerous cellular processes and metabolic activities, notably fatty acid synthesis, amino acid catabolism and gluconeogenesis (making glucose from protein).

Biotin helps to support healthy insulin sensitivity and pancreatic health, and is crucial for the utilization of glucose for energy. Biotin also is involved in gene transcription regulation and immune system health. A deficiency of biotin is characterized by hair loss and dermatitis (skin rashes). Biotin has been researched for its ability to help promote healthy hair, skin and nails.