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Riboflavin +rI-bu-!flA-vun

(Vitamin B2)

by Larry E. Johnson, MD, PhD

Riboflavin (vitamin B2) is essential for the processing (metabolism) of carbohydrates (to produce energy) and amino acids. It also helps keep mucous membranes (such as those lining the mouth) healthy. Riboflavin is not toxic.

Riboflavin Deficiency

  • People have painful cracks in the corners of the mouth and on the lips, scaly patches on the head, and a magenta mouth and tongue.

  • The diagnosis is based on symptoms, urine tests, and response to riboflavin supplements.

  • High doses of riboflavin supplements, usually taken by mouth, can correct the deficiency.

Riboflavin deficiency usually occurs with deficiencies of other B vitamins. It usually results from not consuming enough protein and calories. Chronic disorders (such as recurrent diarrhea, liver disorders, and chronic alcoholism) and malabsorption disorders increase the risk of riboflavin deficiency, as can hemodialysis and peritoneal dialysis—procedures that filter the blood (see Dialysis : Types of Dialysis).


Symptoms may vary. Painful cracks form in the corners of the mouth and on the lips. The mouth and tongue are sore, and the tongue may turn magenta. Red, greasy, scaly (seborrheic) patches may appear around the nose, between the nose and the lips, on the ears and eyelids, and in the genital area.


  • Physical examination

  • Urine tests

  • Relief of symptoms when riboflavin supplements are taken

The diagnosis is based on symptoms and evidence of general undernutrition (see Undernutrition : Symptoms). The diagnosis is confirmed by measuring riboflavin excreted in urine or by giving riboflavin supplements, which relieve symptoms if deficiency is the cause.

Prevention and Treatment

  • Riboflavin supplements

  • Sometimes riboflavin given by injection

As a preventive measure, people who are undergoing hemodialysis or peritoneal dialysis or who have a malabsorption disorder should take riboflavin supplements.

High doses of riboflavin are taken by mouth until symptoms resolve. If this treatment is ineffective, riboflavin can be given by injection into a muscle. Supplements of other B vitamins are also taken.