Component of flavins FAD and FMN, used as cofactors in redox reactions eg, the succinate dehydrogenase reaction in the TCA cycle.

Deficiency: - Individuals who do not consume dairy products (e.g., patients with lactose intolerance), and in individuals who do not eat meats or eggs. - Cheilosis (inflammation of the lips, scaling, fissures at the corners of the mouth)- Corneal vascularizationThe 2 Cs of B₂- Glossitis- Stomatitis (hyperemic/edematous oropharyngeal mucous membranes, sore throat)- Normocytic-normochromic anemia- Seborrheic dermatitis

Diagnosis: activity coefficient of erythrocyte glutathione reductase in the absence and presence of FAD