Vitamin B2, also called riboflavin, is one of the eight B vitamins your body needs for energy production. It’s a yellow crystalline compound that belongs to the water-soluble B vitamin family, and it works primarily as a component of two coenzymes (FAD and FMN) involved in hundreds of metabolic reactions.

Without adequate riboflavin, your body struggles to break down carbohydrates, fats, and proteins for energy. It’s also essential for maintaining healthy mucous membranes, corneas, nerve sheaths, and red blood cell production. The vitamin contributes to overall nervous system function, plus the health of your skin, nails, eyes, and hair.

Why deficiency matters

When you don’t get enough riboflavin, the symptoms can be frustratingly vague: tiredness, dry or cracked skin, angular cheilitis (cracks at the corners of the mouth), and eye fatigue. What makes it worse is that riboflavin deficiency can prevent other B vitamins from working properly, including vitamin B6, niacin, and folic acid.

According to the NHS, most people in the UK get enough riboflavin from their diet 1. Good dietary sources include:

Milk and dairy products (one of the richest sources)
Eggs
Meat, particularly organ meats like liver
Dark green leafy vegetables such as spinach and broccoli
Fortified breakfast cereals
Mushrooms

The recommended daily intake for adults is approximately 1.1-1.3 mg. Because riboflavin is water-soluble, your body doesn’t store it in large quantities, so you need a regular supply from food. Genuine deficiency is relatively uncommon in developed countries, though certain groups (older adults, people with chronic alcoholism, those with malabsorption conditions) are at higher risk.

What does the research say about riboflavin’s benefits?

I’ve looked through the clinical evidence on four commonly discussed uses for riboflavin supplementation. The quality of evidence varies considerably.

1. Migraine prevention

This is where riboflavin has the strongest evidence, and it’s the use that generates the most interest.

Migraine is a neurological condition affecting roughly 12% of the population, with women experiencing it about three times more often than men. The throbbing pain, light sensitivity, and nausea can completely disrupt daily life. Current thinking suggests that impaired mitochondrial energy metabolism may play a role in migraine pathophysiology, and since riboflavin is essential for mitochondrial function, supplementation might help.

A controlled study involving 55 migraine patients compared high-dose riboflavin (400 mg daily) against placebo over three months. The riboflavin group experienced significantly fewer migraine attacks, with reduced frequency and severity 2.

Research in younger populations has shown similar results. A retrospective study of 41 children and adolescents found that riboflavin at doses of 200-400 mg daily reduced attack frequency by about 50% and seizure intensity by 21% in approximately 68% of participants compared with their baseline 3.

More recently, a 2021 meta-analysis pooled data from 8 randomised controlled trials and 1 controlled trial involving 673 migraine patients. The analysis found that vitamin B2 supplementation at 400 mg daily for three months significantly reduced migraine days, duration, frequency, and pain scores 4.

My take: The evidence for migraine prevention is genuinely encouraging. The American Academy of Neurology and the American Headache Society have both recognised riboflavin as “probably effective” for migraine prevention. The 400 mg dose used in studies is much higher than the recommended daily allowance (about 300 times higher), but riboflavin has an excellent safety profile. The main catch is that you need to take it consistently for two to three months before seeing benefits. This isn’t a quick fix for an active migraine.

2. Cataract risk

Cataracts develop when the lens proteins in your eye become clouded, preventing light from forming a clear image on the retina. Vision gradually becomes blurry or ghosted. It’s essentially an aging phenomenon; by age 80, roughly half of people have some degree of cataract, though the rate of progression varies enormously between individuals.

The theory behind riboflavin and cataracts relates to its antioxidant properties. Oxidative damage to lens proteins is thought to contribute to cataract formation, and riboflavin helps maintain glutathione, one of your body’s key antioxidants.

An Australian cross-sectional study examined dietary intake and cataract prevalence in 2,900 men and women. Those in the top quintile for riboflavin intake had 50% lower rates of cataract compared with those in the lowest quintile 5.

A five-year observational study following 408 participants found that dietary riboflavin intake was inversely correlated with lens opacification; people who consumed more riboflavin showed less lens clouding over time 6.

The catch: These are observational studies showing correlations, not causation. People who eat more riboflavin-rich foods might also have healthier overall diets and lifestyles. To date, there have been no double-blind controlled trials specifically testing riboflavin supplementation for cataract prevention. I’d be cautious about drawing strong conclusions here. Getting adequate riboflavin through diet seems sensible for general eye health, but I wouldn’t stake much on supplements specifically preventing cataracts without better evidence.

3. Colorectal cancer

Colorectal cancer is among the most commonly diagnosed cancers globally, accounting for roughly 9% of all cases. Incidence increases significantly after age 40, with about 90% of cases occurring after 50. However, recent years have seen increasing diagnoses in younger adults, possibly related to dietary changes 7.

Researchers have investigated whether B vitamin intake might influence colorectal cancer risk. Riboflavin participates in one-carbon metabolism, a biochemical pathway involved in DNA synthesis and repair. Disruptions to this pathway could theoretically affect cancer development.

A large observational study followed 88,045 postmenopausal women and examined the relationship between B vitamin intake and colorectal cancer. Higher dietary intake of riboflavin and vitamin B6 was associated with significantly lower rates of colorectal cancer compared with lower intake 8.

Reality check: This is preliminary associational data from a single cohort study. The relationship between B vitamins and cancer is complicated, and other large studies have found no protective effect or even potential harm with certain B vitamins at high doses. A 2018 meta-analysis of randomised controlled trials with over 74,000 participants found that B vitamin supplementation had no effect on overall cancer incidence or mortality 9. The current evidence doesn’t support taking riboflavin specifically to prevent colorectal cancer.

4. Multiple sclerosis

Multiple sclerosis is an autoimmune condition where the immune system attacks the myelin sheath surrounding nerve fibres in the central nervous system. This causes a wide range of disabling symptoms including sensory impairment, vision loss, and motor dysfunction. The condition typically appears between ages 20 and 40, affects women twice as often as men, and is most common in Northern European populations 10.

The rationale for investigating riboflavin in multiple sclerosis relates to its role in myelin production and mitochondrial function. Some researchers hypothesised that supplementation might help protect or repair damaged nerve tissue.

A double-blind controlled study tested this hypothesis by giving 29 multiple sclerosis patients either riboflavin (10 mg daily) or placebo for six months. The outcome was disappointing: riboflavin did not improve scores on the Expanded Disability Status Scale and showed no benefit over placebo for disability symptoms 11.

My assessment: The evidence here is straightforwardly negative. A single small trial isn’t definitive, but the results don’t support riboflavin for multiple sclerosis. The dose used (10 mg) was also much lower than the high doses used in migraine studies (400 mg), so there’s a theoretical argument that higher doses might be worth testing. That said, I wouldn’t recommend riboflavin for multiple sclerosis based on current evidence.

Side effects and safety

Riboflavin is generally very safe, even at high doses. Because it’s water-soluble, excess amounts are excreted in urine rather than stored in the body. The NHS notes that taking high doses is unlikely to cause harm 1.

The most noticeable effect of high-dose supplementation is bright yellow or orange urine. This is completely harmless and simply reflects the vitamin being excreted. It can be startling if you’re not expecting it, but it’s not a sign of any problem.

At very high doses, some people report:

Mild itching
Increased sensitivity to light
Tingling or numbness

These side effects are uncommon and resolve when supplementation stops.

Contraindications and precautions

While riboflavin is generally safe, certain situations warrant extra caution:

Tetracycline antibiotics: Riboflavin may interfere with the absorption of tetracycline antibiotics (used for acne and some infections). If you’re taking tetracycline, separate your riboflavin supplement by at least two hours.

Other medications: Several drug classes may reduce riboflavin absorption or increase requirements, including:

Tricyclic antidepressants (amitriptyline, nortriptyline)
Anticholinergic medications
Certain antipsychotic medications
Some epilepsy medications (phenytoin, phenobarbital)
Thiazide diuretics

Liver or kidney impairment: If you have significant liver or kidney problems, discuss any supplementation with your GP before starting. While riboflavin is generally safe, impaired organ function can affect how your body processes any supplement.

Pregnancy and breastfeeding: Riboflavin requirements increase during pregnancy and breastfeeding. The NHS recommends that pregnant women can usually get sufficient riboflavin through diet, but if you’re considering supplementation beyond a standard prenatal vitamin, consult your midwife or doctor.

Practical recommendations

If you’re considering riboflavin supplementation, here are some practical points:

For migraine prevention: The evidence supports 400 mg daily for at least two to three months before assessing effectiveness. This is substantially higher than standard multivitamin amounts. Discuss with your GP first, particularly if you take other medications.

For general health: Most people get adequate riboflavin from diet. Good sources include dairy products, eggs, meat, and fortified cereals. Supplementation isn’t necessary for most healthy adults eating a varied diet.

What to expect: Don’t be alarmed by bright yellow urine; it’s normal with B2 supplementation. If you experience light sensitivity or other unusual symptoms, reduce your dose or stop supplementation.

Who might benefit: People most likely to benefit from riboflavin supplementation include those with frequent migraines, vegans (who may have lower intake if not eating fortified foods), people with malabsorption conditions, and those taking medications that deplete riboflavin.

Summary

Riboflavin is an essential B vitamin that most people obtain adequately through diet. The strongest evidence for supplementation relates to migraine prevention, where doses of 400 mg daily have shown meaningful benefits in clinical trials. The evidence for other proposed benefits (cataracts, cancer prevention, multiple sclerosis) is either preliminary or negative.

The safety profile is excellent, with the main side effect being harmless yellow discolouration of urine. Drug interactions exist but are generally manageable with proper timing.

If you experience frequent migraines, riboflavin is worth discussing with your doctor as a low-risk addition to your treatment plan. For most other purposes, focus on getting adequate riboflavin from food rather than supplements.

References

NHS. B vitamins and folic acid. https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-b/
Schoenen J, Jacquy J, Lenaerts M. Effectiveness of high-dose riboflavin in migraine prophylaxis. Neurology. 1998;50(2):466-70. https://pubmed.ncbi.nlm.nih.gov/9484373/
Condò M, et al. Riboflavin prophylaxis in pediatric and adolescent migraine. J Headache Pain. 2009;10(5):361-5. https://pubmed.ncbi.nlm.nih.gov/19649688/
Chen YS, et al. Effect of Vitamin B2 supplementation on migraine prophylaxis: a systematic review and meta-analysis. Nutr Neurosci. 2022;25(9):1801-1812. https://pubmed.ncbi.nlm.nih.gov/33779525/
Cumming RG, Mitchell P, Smith W. Diet and cataract: the Blue Mountains Eye Study. Ophthalmology. 2000;107(3):450-6. https://pubmed.ncbi.nlm.nih.gov/10711880/
McNulty H, et al. Riboflavin, MTHFR genotype and blood pressure: A personalized approach to prevention and treatment of hypertension. Mol Aspects Med. 2017;53:2-9. https://pubmed.ncbi.nlm.nih.gov/15824226/
Siegel RL, Miller KD, Jemal A. Colorectal cancer statistics. CA Cancer J Clin. 2017;67(3):177-193. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2796096/
Zschabitz S, et al. B vitamins and risk of colorectal cancer: results from the Women’s Health Initiative Observational Study. Cancer Epidemiol Biomarkers Prev. 2013;22(1):105-14. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3545682/
Mocellin S, et al. Vitamin B supplementation and cancer risk: overview and meta-analysis of randomized controlled trials. Carcinogenesis. 2018;39(3):406-413. https://pubmed.ncbi.nlm.nih.gov/29216732/
Compston A, Coles A. Multiple sclerosis. Lancet. 2008;372(9648):1502-17. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3351877/
Naghashpour M, et al. Riboflavin supplementation to patients with multiple sclerosis does not improve disability status nor is riboflavin supplementation correlated to homocysteine. Int J Vitam Nutr Res. 2013;83(5):281-90. https://pubmed.ncbi.nlm.nih.gov/25305223/