Does riboflavin (B2) interact with any medications?

The NIH states riboflavin has no known clinically relevant interactions with medications.

What this means for you

Riboflavin is not known to have any clinically relevant interactions with medications, and no upper limit was set for it, because high intakes have not produced harm.

That is an unusually clean answer for a nutrient page, so the useful thing to add is what a large dose actually does. It turns urine bright yellow, which is harmless and is simply the excess leaving. People who start a B complex often notice this and worry about it.

If you are taking riboflavin for migraine, the question is benefit rather than safety, and the answer splits by age. Pooling 22 randomised trials of supplements for migraine, riboflavin cut attacks by about one and a third a month in adults. Two small randomised studies in children found no reduction in either the number of headaches or their severity.

One practical note for anyone on several supplements at once. Riboflavin is water-soluble and the excess leaves quickly, so a missed day means nothing and a double dose achieves nothing. If you are short of it, the fix is usually dairy, eggs or a fortified product rather than a dedicated tablet, because those foods carry the rest of the B vitamins alongside it.

The blood pressure claim, and what a review did to it

If you have read that riboflavin lowers blood pressure sharply in people with a particular gene variant, that claim exists, it is specific, and it has now been examined properly.

The variant is MTHFR 677TT, carried by 5 to 15 per cent of most populations, about 20 per cent in parts of Italy and China and about 30 per cent in Mexico. The biology is neat. That version of the enzyme binds its FAD cofactor less well, and FAD comes from riboflavin. Three trials reported blood pressure falling by 6 to 13 mmHg in people with the TT genotype after 16 weeks.

Unsettled. Cochrane looked for that effect in 2025 and would not stand behind it. Four small trials, most at high risk of bias. Systolic pressure came out at a mean difference of -1.94 mmHg, with a confidence interval running from -5.74 to 1.86, which contains no effect at all. Diastolic came out at -3.03 with an interval from -5.97 to -0.09, technically clear of zero and rated very low certainty. The three trials behind the striking headline figure are part of the same body of work the review judged too weak to rely on. Plausible mechanism, striking early results, and a pooled answer of nobody knows. If you carry that variant, this is worth following and not yet worth taking a tablet for.

Established. The migraine result is on firmer ground, and it is smaller than the way it gets sold. Riboflavin reduced attacks by about 1.34 a month. In the same pooled comparison, magnesium cut 2.51 attacks along with severity and monthly migraine days, and CoQ10 cut 1.73 attacks plus severity and duration. Riboflavin works, modestly, and came third of three.

A real interaction, running the unexpected way

Established. Riboflavin does have a proper drug interaction. The blood thinner ticagrelor raised the ratio of peak to fasting plasma riboflavin by 1.20-fold against placebo, because the two share transporters in the gut wall, BCRP and MRP4, and ticagrelor blocks both. Note which way it points. The drug pushes riboflavin up rather than down, so this is a fact about how the gut handles the vitamin rather than a reason for anyone on ticagrelor to take a supplement.

Written from the evidence cards and the data on this page, then checked back against the sources. Bioma Learn has no human medical reviewer at this time and we say so rather than invent one. Information, not medical advice. How we verify.

Full guide: Riboflavin: a milk and egg vitamin, and what the migraine trials really show