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Water-soluble vitamin

Vitamin B2

riboflavin

Energy metabolism (FAD/FMN), antioxidant recycling, activation of B6 and folate

Essential nutrient

Reference intakes (RDA or AI) are set by the National Academies of Sciences, Engineering, and Medicine. Deficiency thresholds come from clinical and WHO guidance.

At a glance

Women, 19-50

1.1 mg

Men, 19-50

1.3 mg

Upper limit (adults)

Not established

How common is deficiency?

Uncommon in high-income countries; more common in low-income regions with little dairy/meat

Food sources

Animal sources

Milk, yogurt, cheese, eggs, beef liver, lean meat, salmon

Plant sources

Fortified cereals, almonds, mushrooms, spinach, enriched bread

Deficiency and testing

Signs of deficiency

Cracked lips and corners of mouth (angular stomatitis), sore red tongue (magenta), sore throat, seborrheic dermatitis, eye sensitivity, anemia

Who is at higher risk

Vegans with limited fortified foods, alcohol use disorder, pregnant/lactating women, adolescents with poor diets, malabsorption

How it is tested

Erythrocyte glutathione reductase activity coefficient (EGRAC); urinary riboflavin excretion

Cut-offs

EGRAC >1.4 = deficiency; urinary riboflavin <27 mcg/g creatinine

Symptoms are not specific. Only a clinician with the right tests can tell whether you are deficient.

Supplement forms

Common forms

riboflavin, riboflavin-5'-phosphate (FMN, 'active'), in B-complex.

More effective

plain riboflavin (efficient absorption up to about 27 mg per dose; high-dose 400 mg/day is used for migraine prevention) with food.

Less effective

the 'active' riboflavin-5'-phosphate gives no proven advantage (it is converted back to riboflavin in the gut before absorption); doses above about 30 mg per sitting (excess is excreted, urine turns bright yellow).

Safety, interactions and halal notes

Safety and interactions

Upper limit for adults: Not established. Going above the upper limit over time can cause harm, so check labels and talk to a clinician before high-dose supplements.

Halal note

The nutrient itself is not a halal question. For supplements, check the delivery form: gelatin (pork or non-halal bovine), capsule shells, glycerin, and alcohol-based carriers need halal certification. Ask for the halal certificate, not just a label claim. This is general guidance, not a certification.

Frequently asked questions

How much Vitamin B2 do adults need per day?

Women 19-50: 1.1 mg. Men 19-50: 1.3 mg. Upper limit: Not established. Needs change with age, pregnancy and health conditions.

What are the signs of Vitamin B2 deficiency?

Cracked lips and corners of mouth (angular stomatitis), sore red tongue (magenta), sore throat, seborrheic dermatitis, eye sensitivity, anemia. These signs are not specific, so only a clinician with the right tests can confirm a deficiency.

What are the best food sources of Vitamin B2?

Animal sources: Milk, yogurt, cheese, eggs, beef liver, lean meat, salmon. Plant sources: Fortified cereals, almonds, mushrooms, spinach, enriched bread.

Which form of Vitamin B2 supplement is best?

plain riboflavin (efficient absorption up to about 27 mg per dose; high-dose 400 mg/day is used for migraine prevention) with food.

Sources

NIH Office of Dietary Supplements fact sheet

← Back to the full nutrient guide

This page is for education only and is not medical advice. These statements have not been evaluated by the Food and Drug Administration. Supplements are not intended to diagnose, treat, cure or prevent any disease. Talk to a qualified clinician before starting a supplement, especially if you are pregnant, breastfeeding, take medicine or have a medical condition. Daily needs are US reference intakes for adults 19-50.

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