Riboflavin deficiency usually occurs in combination with other vitamin deficiencies. Dietary inadequacy, interactions with medications, alcohol use disorder, and other causes of protein–calorie undernutrition are the most common causes.
Manifestations of riboflavin deficiency include cheilosis, angular stomatitis, glossitis, seborrheic dermatitis, weakness, corneal vascularization, and anemia.
Riboflavin deficiency can be confirmed by measuring the riboflavin-dependent enzyme erythrocyte glutathione reductase. Activity coefficients greater than 1.2–1.4 are suggestive of riboflavin deficiency. Urinary riboflavin excretion and serum levels of plasma and red cell flavins can also be measured.
When suspected, riboflavin deficiency is usually treated empirically with foods such as meat, fish, and dairy products or with oral preparations of the vitamin. Administration of 5–15 mg/day until clinical findings resolve is usually adequate. Riboflavin can also be given parenterally, but it is poorly soluble in aqueous solutions.