A yellow-orange water-soluble vitamin that forms the cofactors FAD and FMN, used by dozens of enzymes in energy metabolism and antioxidant recycling. Dietary deficiency is uncommon where dairy and fortified cereals are eaten.
Riboflavin is the B vitamin with one specific, moderately supported non-deficiency use: migraine. A small randomised trial found 400 mg/day roughly halved attack frequency in a substantial proportion of participants, and the finding earned it a place in several headache-society guidelines, though subsequent trials — particularly in children — have been less impressive. Beyond migraine, riboflavin supplementation on an adequate intake has no demonstrated effect. It also turns urine bright yellow within hours, which is harmless, universal, and frequently mistaken for evidence that a supplement is working.
Sold as
Tablet, Capsule, Riboflavin-5-phosphate (activated form), Component of B-complex
Also known as
Vitamin B2, Riboflavin-5-phosphate, Lactoflavin
Regulation: No Tolerable Upper Intake Level has been established, because absorption is limited and surplus is excreted. Sold as a dietary supplement with no pre-market efficacy review; the migraine dose of 400 mg/day is more than 300 times the RDA.
What the research used
The amounts, forms and durations published trials of Riboflavin (vitamin B2) actually administered.
These are the amounts published trials administered — not a recommendation, and not a dose to copy. Trial participants were screened, supervised and given a characterised preparation. What is in a retail bottle is frequently not what was studied, and the amount that suits one person is not general advice.
Studied for Recommended Dietary Allowance, adults
1.1–1.3 mg
Strong
1.1 mg/day for women and 1.3 mg/day for men. Deficiency is largely confined to low dairy intake combined with low fortified-cereal intake, and often occurs alongside other B vitamin shortfalls.
Studied for Migraine prophylaxis trials
400 mg
Moderate
Tablet, daily · 3–4 months
From a small randomised trial in adults reporting a substantial reduction in attack frequency. Paediatric trials have generally been negative, and the adult result has limited independent replication.
This is general information about food, not medical advice. It cannot diagnose, treat or replace guidance from a clinician who knows your history.
When it was taken
Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.
None of the timings below were directly compared in a trial. They reflect how the research happened to dose, or what the pharmacology implies — which is not the same as a timing being better.
🍽️With food
Limited
Absorption is modestly better with food, and riboflavin uptake saturates at around 25–30 mg per dose regardless — so most of a 400 mg tablet is never absorbed. Splitting doses is sometimes advised on that basis, though migraine trials used a single daily dose.
Timing was not directly compared. This reflects convention or how the compound behaves in the body, not a trial showing this window works better.
The evidence in depth
Best supported: Moderate
What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how promising the supplement sounds. How we rate evidence.
Riboflavin at 400 mg/day reduced migraine frequency compared with placebo in a small randomised trial and is included in some headache guidelines as a low-risk option. Later trials, especially in children, have not consistently reproduced it, and the evidence base remains small.
What may be going on: Riboflavin is a precursor of flavin cofactors required for mitochondrial electron transport; impaired mitochondrial energy metabolism is one of the long-standing hypotheses in migraine.
Moderate evidence. Several human studies point the same way, with real caveats.
In people homozygous for the MTHFR 677TT variant, riboflavin supplementation has lowered blood pressure in several small trials from one research group. The effect appears specific to that genotype and has not been widely replicated elsewhere.
What may be going on: Riboflavin is the cofactor for MTHFR, and the TT variant produces an enzyme with reduced affinity for it — a genuinely genotype-dependent nutrient effect.
Limited evidence. Early human work, or mostly lab and animal research.
There is not enough evidence that riboflavin improves energy in people whose intake is adequate. Its role in energy-producing enzymes is real, which is not the same as a supplement producing a noticeable effect on top of sufficiency.
Not enough evidence. Not enough human research to say anything useful yet.
Randomised controlled trial · Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research · 2022 · PMID 36128889
Deep research mode adds each paper’s own conclusion and stated limitations.
Things to know
Interactions, contraindications and dose limits, most serious first. Concentrated extracts interact with medication in ways the whole plant does not, so this section carries more weight here than it does on a food page.
Interaction
Interferes with some laboratory assays and photosensitising drugs
High-dose riboflavin can interfere with urinary catecholamine and some fluorometric assays. Riboflavin is also photosensitising in high concentrations, which theoretically adds to drugs that cause photosensitivity.
Worth knowing
A migraine dose is a therapeutic decision
The 400 mg/day migraine regimen is more than 300 times the dietary requirement and is intended to run for months before any assessment. Self-managing headache without a diagnosis risks missing conditions that need investigation.
Worth knowing
Bright yellow urine is expected and meaningless
Riboflavin is a fluorescent yellow pigment and unabsorbed surplus colours urine within hours. It indicates that you took a B vitamin, nothing more — and it is the most common reason people believe a multivitamin is "working".
Worth knowing
Degraded by light
Riboflavin breaks down rapidly in light, in food and in the bottle. Products stored in clear containers on a bright shelf may contain less than the label states by the time they are used.
In the food catalogue
The whole-food form, where one exists. The evidence for a concentrated extract rarely transfers to the food, or the other way round — these are cross-links, not equivalents.