Riboflavin (vitamin B2) is a water-soluble B vitamin that is part of two coenzymes the body uses to make energy and to process fats, drugs and steroids. As a supplement it is used to cover low intake and has been studied mainly for preventing migraine headaches.
Also known as: vitamin B2, riboflavin 5'-phosphate, FMN.
ODS lists a Recommended Dietary Allowance of 1.3 mg a day for men and 1.1 mg for women (1.4 mg in pregnancy, 1.6 mg while breastfeeding). No upper limit was set. Multivitamins commonly provide 1.3 mg. The migraine trial ODS describes used 400 mg a day. These are study protocols, not a recommendation.
It is sold in the US as a dietary supplement. Under the 1994 dietary supplement law (DSHEA), FDA does not approve dietary supplements before they are marketed, and the maker, not FDA, is responsible for safety and labeling. ODS says riboflavin deficiency is extremely rare in the US; people at higher risk include vegans and people who eat little dairy, and vegetarian athletes.
On migraine, ODS says some, but not all, of a few small studies found a benefit. In a trial of 55 adults, 400 mg a day reduced migraine attacks by two a month compared with placebo; two small trials in children found that 50 to 200 mg a day did not reduce headaches. The American Academy of Neurology and American Headache Society concluded that riboflavin is probably effective for preventing migraine, and the Canadian Headache Society also supports it while noting the evidence is low quality. Data on cancer prevention are limited and mixed.
Safety, per ODS: no adverse effects have been reported from high intakes, including 400 mg a day for at least 3 months, so no upper limit was set, but the Food and Nutrition Board urges caution with excessive amounts. The body absorbs little from single doses above 27 mg. Riboflavin is yellow, and discolored urine is a known minor side effect. ODS says riboflavin has no known clinically relevant interactions with medicines.
We could not find a single published half-life or time to peak for riboflavin that applies to a supplement dose, so we do not list one. ODS says the body absorbs little riboflavin from single doses above 27 mg and stores only small amounts; the rest is not absorbed or leaves in the urine.
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