Riboflavin (Vitamin B2) has a dimethylisoalloxazine ring bound to ribitol. Riboflavin is the precursor of FMN and FAD. Riboflavin is degraded to inactive products on exposure to visible light.

Riboflavin deficiency shows glossitis, sore throat, and dermatitis. Infants who are under phototherapy for hyperbilirubinemia may experience riboflavin deficiency.