Riboflavin was originally recognized as a growth factor in 1879 and named vitamin B2 according to the British nomenclature system. It was first isolated from egg whites in 1934 and synthesized in 1935.1,2 Riboflavin fluoresces yellow-orange and gives the yellow-white hue to egg whites and milk. Riboflavin has two active coenzyme forms, riboflavin 5’-phosphate (R5P; flavin mononucleotide [FMN]) and flavin adenine dinucleotide (FAD). Dietary sources include milk, eggs, meats, yogurt, broccoli, almonds, cheese, soy, fortified grains, and dark green vegetables, in descending order of concentration.3 Normal colonic bacteria synthesize riboflavin, contributing to a soluble pool of the vitamin that can be utilized in addition to dietary intake.2 As one of the family of B vitamins, riboflavin contributes to cellular growth, enzyme function, and energy production. FAD is a cofactor in many reactions of intermediary metabolism, such as carbohydrate, fat, and amino acid synthesis; FAD and R5P are also necessary for the activation of other vitamins and enzyme systems. Folate and pyridoxine are vitamins that rely on riboflavin for activation. Clinically, riboflavin has several applications due to its ubiquitous nature in metabolism. Research supports the use of riboflavin in anemia, cataracts, hyperhomocysteinemia, migraine prophylaxis, and alcoholism. A riboflavin deficiency can result in angular stomatitis, seborrhea, glossitis, neuropathy, and anemia.