Vitamin B2

vitamin

What is it

Vitamin B2, also known as riboflavin, is an essential water-soluble B vitamin required for energy metabolism, growth, red blood cell production, and the conversion of other nutrients (vitamins B6 and folate) into their active forms. Severe deficiency causes ariboflavinosis, with symptoms including cracked lips, sore throat, and skin issues.

How it works

Riboflavin is converted in the body to two active coenzyme forms: flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). These coenzymes participate in numerous redox (oxidation-reduction) reactions in cellular energy production, particularly in the electron transport chain that generates ATP, and in the metabolism of fats, carbohydrates, and proteins. Riboflavin is required for the metabolism of other nutrients including vitamin B6 (conversion to pyridoxal-5-phosphate), folate (conversion to active forms), and niacin (production from tryptophan). It is also essential for maintaining glutathione in its reduced form via the enzyme glutathione reductase, supporting cellular antioxidant defense. Riboflavin is absorbed in the small intestine, with the absorption capacity limited at a single dose (around 27 mg). Excess is excreted in urine, giving it the characteristic bright yellow color often seen after taking B-complex supplements. Body stores are limited, so regular intake is needed.

Evidence for 6 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Ariboflavinosis prevention

Grade A

Strong evidence

Riboflavin reliably prevents and treats riboflavin deficiency (ariboflavinosis), with symptoms including cracked lips, sore throat, and skin issues.

Maintenance of normal energy metabolism

Grade A

Strong evidence

Riboflavin is essential for normal energy production from food. Deficiency impairs cellular ATP generation.

Migraine prevention

Grade B

Good evidence

Multiple clinical trials suggest 400 mg of riboflavin daily for 3 months may reduce migraine frequency and severity. Effects develop slowly; allow 8 to 12 weeks of consistent use.

Anemia (in deficiency)

Grade B

Good evidence

Riboflavin is required for normal red blood cell production. Deficiency can cause anemia, which responds to riboflavin supplementation.

Cataract risk

Grade C

Moderate evidence

Some observational research links higher riboflavin intake to lower cataract risk. Intervention evidence is more limited.

MTHFR genetic variants

Grade C

Moderate evidence

People with certain MTHFR variants may benefit from higher riboflavin intake to support folate metabolism and homocysteine reduction. Personalized assessment is helpful.

3 commercial forms

Riboflavin (basic form)

Standard form in most multivitamins and supplements.

Well-absorbed; converted to active FMN and FAD in the body.

Riboflavin-5-phosphate (R5P)

Already activated form (FMN); bypasses one conversion step.

May be useful in individuals with conversion issues. More expensive.

Riboflavin in B-complex formulas

Combined with other B vitamins for synergistic support.

Most common way to supplement. Provides balanced B vitamin intake.

Dosage

The RDA for riboflavin is 1.3 mg/day for men and 1.1 mg/day for women, with higher needs in pregnancy (1.4 mg/day) and breastfeeding (1.6 mg/day). There is no established Tolerable Upper Intake Level. Therapeutic doses for migraine prevention have used 400 mg per day.

When and how to take it

WHEN: Take riboflavin at any time of day. With or without food are both acceptable. HOW: Take with water. Most B-complex supplements provide riboflavin alongside other B vitamins. For migraine prevention, the 400 mg dose is typically taken once daily for several months to evaluate effects.

Food sources

Food	Amount	%DV
Beef liver	3 oz	224%
Fortified breakfast cereals	1 serving	100%
Milk	1 cup	26%
Yogurt (plain)	1 cup	35%
Eggs	1 large	17%
Almonds	1 oz	23%
Spinach	1 cup cooked	33%
Salmon	3 oz	38%

Safety

Riboflavin has an excellent safety record with no known toxicity. The most notable effect of high-dose supplementation is bright yellow urine, which is harmless. There is no established Tolerable Upper Intake Level. Even very high doses are well tolerated.

Who should be cautious

Pregnant and breastfeeding women have increased needs and should ensure adequate intake. People on long-term phenobarbital or certain other medications may need higher intake. Vegetarians and vegans should ensure adequate intake from fortified foods, dairy, or eggs (or supplementation if these are limited). Athletes may have modestly increased needs.

Interactions

Anticholinergic drugs may decrease riboflavin absorption. Tricyclic antidepressants and probenecid may also affect riboflavin levels. Phenobarbital may increase the breakdown of riboflavin in the liver. Doxorubicin (a chemotherapy drug) may be affected by riboflavin's role in cellular oxidation; consult an oncologist.

Frequently asked questions

Why does my urine turn bright yellow after taking B vitamins?⌄

Excess riboflavin is excreted in urine, producing a bright yellow color. This is harmless and indicates that you have absorbed more riboflavin than your body needs immediately.

Does riboflavin really prevent migraines?⌄

Yes, in some people. Multiple trials suggest 400 mg per day for 3 months may reduce migraine frequency and severity. Effects develop slowly; allow 8 to 12 weeks before evaluating effects.

Can I get enough from food?⌄

Yes, easily, if you consume dairy, eggs, meat, fortified cereals, and vegetables regularly. Vegans should pay particular attention to fortified plant milks, nutritional yeast, and fortified cereals.

Is high-dose riboflavin safe?⌄

Yes. Riboflavin has an excellent safety profile with no established Upper Intake Level. Even 400 mg daily (used for migraines) is well tolerated. Bright yellow urine is the main visible effect.

Who is at risk for deficiency?⌄

People with very restricted diets, chronic alcohol use disorder, malabsorption conditions (Crohn's, celiac), or hypothyroidism may have reduced riboflavin status. Pregnant and breastfeeding women have increased needs.

References

NIH Office of Dietary Supplements - Riboflavin — ODS link
Wikidata: Riboflavin — Wikidata link
PubChem: Riboflavin (CID 493570) — PubChem link

Track Vitamin B2 with Pilora

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Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you're pregnant, breastfeeding, on medications, or managing a chronic condition.