Vitamin B2 for MTHFR Mutation

The short answer: if you carry two copies of the C677T MTHFR mutation, riboflavin is the nutrient with the most specific evidence for you. In a placebo-controlled trial, 1.6 mg of vitamin B2 a day for 12 weeks lowered homocysteine by 22% in TT adults, and by 40% in those who started with lower riboflavin status, with no effect in CC or CT adults (McNulty 2006). In three blood pressure trials, the same dose lowered systolic pressure in TT carriers who were already on medication (Horigan 2010; Wilson 2012; Wilson 2013).

That is a striking, genotype-specific result, and it is cheap and safe to act on. But it rests on one research group in Northern Ireland. A 2025 Cochrane review pooled the riboflavin trials and called the blood pressure evidence very uncertain, with most trials at high risk of bias (Bradbury 2025). We rate it likely to help TT carriers, with preliminary evidence, until someone else repeats it.

MTHFR needs flavin adenine dinucleotide (FAD), made from riboflavin, as its cofactor. People with the TT genotype have reduced enzyme activity because the variant enzyme loses its riboflavin cofactor too easily (McNulty 2006). Better riboflavin status is thought to keep more of that cofactor in place.

The population data fit this idea. In 771 Spanish adults, 677T carriers with low or middle folate had 8.2% higher homocysteine than CC adults, but the difference disappeared when riboflavin status was optimal (García-Minguillán 2014). Among 6,076 Irish adults, TT carriers with deficient riboflavin status had three times the odds of hypertension of CC adults with normal status (Ward 2020).

Nobody knows exactly how a better-working MTHFR enzyme lowers blood pressure. The effect appeared independently of homocysteine in the Irish cohort data (Ward 2020). In TT adults, riboflavin raised S-adenosylmethionine (SAM), the body's main methyl donor, and cystathionine, but no other one-carbon metabolites changed (Rooney 2020). These are clues, not an explanation, and none of them shows a change in heart attacks or strokes.

The cofactor story also doesn't make riboflavin a general homocysteine treatment. In 52 older adults with sub-optimal riboflavin status who were not selected by genotype, 1.6 mg a day for 12 weeks did not change homocysteine, while folic acid lowered it by 19.6% (McKinley 2002).

Every MTHFR trial used the same dose: 1.6 mg of riboflavin a day, for 12 weeks in the homocysteine trial and 16 weeks in the blood pressure trials. That is a nutritional dose, only a little above the adult RDA of 1.3 mg for men and 1.1 mg for women set by the US Food and Nutrition Board (NIH ODS). Multivitamins commonly provide 1.3 mg.

No trial in MTHFR carriers has tested higher doses. The 400 mg a day used for migraine prevention is a different use; there is no evidence it does more for MTHFR. The body absorbs little riboflavin beyond about 27 mg from a single dose, and the rest leaves in urine (NIH ODS).

From a register of 680 healthy adults of known genotype, McNulty 2006 randomised 35 TT, 26 CT and 28 CC adults to riboflavin 1.6 mg a day or placebo for 12 weeks. Riboflavin status improved by the same amount in all three groups, but homocysteine responded only in the TT group, falling from 16.1 to 12.5 umol/L (22%, P = 0.003). CC and CT adults showed no change despite being preselected for suboptimal riboflavin status.

Other studies show why the picture isn't simple. In a 4-month folate study of 126 healthy adults, lower riboflavin status went with higher homocysteine, but the effect was not restricted to T-allele carriers (Moat 2003). And when older adults not selected by genotype took riboflavin, homocysteine didn't move (McKinley 2002).

Horigan 2010 randomised patients with premature cardiovascular disease within each genotype group to riboflavin 1.6 mg a day or placebo for 16 weeks; 181 completed. In TT patients, mean blood pressure fell from 144/87 to 131/80 mmHg (P < 0.05), with no response in CT or CC patients. Four years later, 31 TT patients repeated the intervention crossover-style; across both rounds, riboflavin lowered systolic pressure by 9.2 mmHg and diastolic by 6.0 mmHg (Wilson 2012).

Wilson 2013 then tested 91 TT carriers with treated high blood pressure but no overt cardiovascular disease. Over 16 weeks the treatment effect on systolic pressure was 5.6 mmHg (P = 0.033); diastolic pressure did not change significantly. More than 60% of these patients hadn't reached goal blood pressure despite taking several drug classes. The research group's own review summarises the systolic effect across trials as 6 to 13 mmHg (McNulty 2017).

A 2025 Cochrane review included four RCTs with 374 participants and found the effect of riboflavin on blood pressure very uncertain: systolic -1.94 mmHg (95% CI -5.74 to 1.86) and diastolic -3.03 mmHg (95% CI -5.97 to -0.09), both very low-certainty evidence, with three of the four trials at high risk of bias (Bradbury 2025). The review asked about riboflavin for adults generally and ran a genotype subgroup analysis; its verdict reflects how few trials exist, not proof that riboflavin fails in TT carriers.

Observational studies point the same way as the trials. In 400 older adults in northern China, CC carriers with above-median riboflavin had much lower odds of hypertension than TT carriers with below-median riboflavin (OR 0.189) (Zhang 2025), matching the Irish finding (Ward 2020).

No group outside Ulster has run a riboflavin trial in TT carriers. No trial has measured heart attacks, strokes or deaths. No trial has tested riboflavin in pregnancy, although TT carriers have a higher risk of hypertensive disorders of pregnancy and researchers have proposed it (Reilly 2014; Duffy 2025). And no trial has tested people with the A1298C variant alone.

At 1.6 mg a day riboflavin is a nutritional dose. NIH notes that no adverse effects have been reported from high intakes from food or supplements, including 400 mg a day for at least 3 months, so no upper limit has been set; it still urges caution with excessive amounts (NIH ODS). The Cochrane review found riboflavin may make little to no difference to adverse events (Bradbury 2025).

Expect bright yellow urine; it is harmless. People with glucose-6-phosphate dehydrogenase deficiency should know that the usual riboflavin blood test (EGRAC) can't be used for them, so status has to be judged another way (NIH ODS).

NIH states riboflavin is not known to have any clinically relevant interactions with medications. The interplay that matters for MTHFR carriers is with other B vitamins, above all folate, the other half of the MTHFR story. Folic acid at 400 mcg a day was followed by a rise in the share of people with poor riboflavin status, from 52% to 65% (Moat 2003), and low riboflavin goes with low active vitamin B6, most of all in TT carriers (Jarrett 2022).