Vitamin B2 (Riboflavin)
Riboflavin (vitamin B2) is a water-soluble vitamin and the precursor of two coenzymes — flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) — that the body uses across energy metabolism, fatty-acid breakdown, and the handling of other B vitamins. The NHS sets the adult requirement at 1.3 mg a day for men and 1.1 mg for women, and says most people should get all they need from a normal diet (milk, eggs, fortified breakfast cereals, mushrooms). The labelling reference value used for the "%NRV" on a supplement is 1.4 mg. Riboflavin carries nine authorised UK health claims.
Camden Medicals editorial · Last reviewed 12 June 2026 · Next review June 2027
- Cross-checked against
- NHS
- NICE
- BNF
- EFSA
- FSA
Camden's editorial team independently graded each health claim below on the strength of the published evidence — see the grade beside every condition.
- Class
- Vitamin
- Typical daily dose
- Everyday supplement doses are commonly 1.4-10 mg/day (around 100-700% NRV). The migraine-prevention trial dose is 400 mg/day, used under clinical supervision.
- Top use evidence
- Moderate
On this page
What it is
Riboflavin is a water-soluble vitamin (its ribityl side chain gives it both its name and its characteristic yellow colour). The body converts it into two active coenzymes — flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) — which act as the working part of many enzymes in mitochondrial energy metabolism, fatty-acid breakdown, the recycling of other B vitamins (folate, B6 and B12), and antioxidant enzymes such as glutathione reductase.
In a UK diet, riboflavin comes mainly from milk and dairy, eggs, fortified breakfast cereals, mushrooms, and lean meat. The NHS notes that ultraviolet light destroys riboflavin, which is one reason milk is no longer sold in clear glass bottles. It also notes that riboflavin cannot be stored in the body, so a regular dietary supply is needed — most people on a varied diet meet this comfortably.
Supplements use either riboflavin (the parent vitamin) or riboflavin-5-phosphate (the activated FMN form). Both are well absorbed; riboflavin-5-phosphate costs more and appears mainly in specialist preparations. There is no good evidence that one ordinary oral form works meaningfully better than the other at the same dose.
At a glance
- Water-soluble vitamin; the body converts it to the FMN and FAD coenzymes used in everyday energy metabolism.
- NHS adult requirement: 1.3 mg/day (men), 1.1 mg/day (women). Most people get enough from milk, eggs, fortified cereals and mushrooms. Labelling NRV is 1.4 mg.
- Nine authorised UK claims cover energy metabolism, nervous system, mucous membranes, red blood cells, skin, vision, iron metabolism, oxidative-stress protection, and tiredness/fatigue.
- NICE recommends 400 mg/day as a migraine-prevention option for some people — far above the everyday intake and a specialist-supervised, not a general-wellness, dose.
What people use it for
People with a low dietary riboflavin intake (vegan diets without fortified foods, very low dairy intake)
The NHS says most people get all the riboflavin they need from food, with dairy as the principal UK source. People who avoid dairy and fortified foods are the group most likely to fall short; fortified foods or a supplement returns intake to the reference level, at which the authorised claims apply. [1]
Some evidenceModerateAdults considering riboflavin for migraine prevention (specialist-supervised)
NICE Clinical Knowledge Summaries recommend riboflavin 400 mg once a day as a migraine-prevention option that may help some people, alongside the standard preventive medicines. The dose is around 285 times the everyday reference intake; it is taken under clinical supervision, not as a general supplement. [5,6]
Some evidenceLimitedAdults already eating a varied diet who supplement for general "energy" or wellness
For people who are not short of riboflavin, taking more does not add a benefit. The authorised "tiredness and fatigue" claim describes riboflavin supporting normal metabolism at adequacy, not extra energy from extra intake. [1]
Popular, not provenInsufficient
How it works
FAD is the redox cofactor for hundreds of dehydrogenase and oxidase enzymes, including succinate dehydrogenase (Complex II of the mitochondrial electron transport chain) and the acyl-CoA dehydrogenases of fatty-acid breakdown. FMN is the cofactor for NADH dehydrogenase (Complex I) and for the enzyme that activates vitamin B6. Riboflavin is also needed by methylenetetrahydrofolate reductase (MTHFR), the enzyme that produces the active form of folate — so a low riboflavin status can affect folate and B6 pathways, and prolonged riboflavin shortfall can look like an apparent folate or B6 problem on testing.
Common myths
Myth"Yellow urine after a B-vitamin supplement means it is "not absorbing"."
RealityIt means the opposite. Riboflavin is bright yellow; the body absorbs what it needs and the kidneys clear the excess, which colours the urine. Yellow urine after a B-complex is a normal physiological sign, not evidence that the supplement is being wasted.
Myth"Riboflavin cures migraines."
RealityIt does not. The trial evidence is for prevention (fewer attacks over time at 400 mg/day), not a cure, and the effect size is modest. NICE includes riboflavin as one preventive option among several, not a first-line treatment, and clinically significant migraine warrants a proper clinical assessment. [6]
Myth"A higher-dose B2 supplement gives you more energy."
RealityOnly if you were short of it to begin with. The authorised UK claim is that riboflavin contributes to normal energy-yielding metabolism and to the reduction of tiredness and fatigue — a description of it being needed for the system to work, not a promise that extra riboflavin raises energy above normal in someone already replete. [3]
Common online questions
Synthesised from the questions UK shoppers most often ask online about Vitamin B2 (Riboflavin). Each answer is editorial and links to its evidence in the Sources list below.
Why is my urine bright yellow after a B-complex?
Riboflavin (B2) is yellow, and the body excretes whatever it does not need in the urine. Bright yellow urine after a riboflavin or B-complex supplement is normal, lasts a few hours, and is harmless.
Should I take riboflavin for migraines?
This is a question to put to your GP or pharmacist. NICE Clinical Knowledge Summaries do recommend riboflavin 400 mg once a day as a migraine-prevention option that may help some people — but that dose is far higher than an everyday supplement (around 285 times the 1.4 mg reference intake) and is intended to be used under clinical supervision and reviewed for effect. It is one option among several preventive approaches, not a first step for everyone. [6]
Is riboflavin-5-phosphate worth paying more for than plain riboflavin?
For most people, no clear advantage is established. Riboflavin-5-phosphate is the already-activated form, but the gut readily converts ordinary riboflavin too, and there is no good head-to-head evidence that one ordinary oral form works meaningfully better than the other at the same dose. Form naming on the label is useful for transparency; a price premium is not, on its own, a sign of better value.
⚖️ The official position
What may lawfully be claimed about Vitamin B2 (Riboflavin) in Great Britain. This is a regulatory position, not an evidence grade.
A health claim is authorised in Great Britain.
“Riboflavin contributes to normal energy-yielding metabolism”
“Riboflavin contributes to normal functioning of the nervous system”
“Riboflavin contributes to the maintenance of normal mucous membranes”
“Riboflavin contributes to the maintenance of normal red blood cells”
“Riboflavin contributes to the maintenance of normal skin”
“Riboflavin contributes to the maintenance of normal vision”
“Riboflavin contributes to the normal metabolism of iron”
“Riboflavin contributes to the protection of cells from oxidative stress”
“Riboflavin contributes to the reduction of tiredness and fatigue”
This claim is authorised for use in Great Britain under the GB Nutrition and Health Claims regulation. A product may carry it when it provides at least 15% of the UK NRV per recommended daily portion.
Authorised UK health claims
Verbatim from the GB Nutrition and Health Claims Register (Reg 432/2012 as assimilated in GB). A product can carry these claims when it provides at least 15% of the UK NRV per recommended daily portion.
9 authorised claims — show / hide
- "Riboflavin contributes to normal energy-yielding metabolism"
- "Riboflavin contributes to normal functioning of the nervous system"
- "Riboflavin contributes to the maintenance of normal mucous membranes"
- "Riboflavin contributes to the maintenance of normal red blood cells"
- "Riboflavin contributes to the maintenance of normal skin"
- "Riboflavin contributes to the maintenance of normal vision"
- "Riboflavin contributes to the normal metabolism of iron"
- "Riboflavin contributes to the protection of cells from oxidative stress"
- "Riboflavin contributes to the reduction of tiredness and fatigue"
🔬 Camden’s evidence review
The research Camden reviewed, graded on its strength. This is our own appraisal — it sits beneath the official guidance above, never above it.
Riboflavin status and the deficiency syndrome (ariboflavinosis)
ModerateEvidencemoderateRiboflavin is an established essential nutrient. A genuine shortfall produces a recognised syndrome — cracking at the corners of the mouth (angular cheilitis), a sore tongue, and skin changes — that resolves when intake returns to the reference level. UK reference intakes (NHS/COMA) and the EFSA-substantiated GB-NHC function claims anchor riboflavin's role in normal energy metabolism, skin, vision, red blood cells and iron handling. [1,3]
Migraine prevention (prophylaxis), 400 mg/day
LimitedEvidencelimitedA single placebo-controlled randomised trial (Schoenen 1998, 55 patients, 400 mg/day for 3 months) reported fewer migraine attacks on riboflavin than placebo, with about 59 in 100 patients improving by at least half versus about 15 in 100 on placebo. An open-label study without a placebo group (Boehnke 2004) reported a similar reduction in attack frequency. The evidence base is small, but NICE CKS recommends riboflavin 400 mg/day as an option that may help some people; the Canadian guideline NICE cites notes effectiveness may be limited. [5,7,6]
Safety
Riboflavin is very well tolerated at oral supplement doses; the excess is cleared rapidly by the kidneys (harmless yellow urine). High-dose use (400 mg/day for migraine prevention) should be supervised by a clinician.
Talk to your pharmacist or GP first if you:
- You are pregnant or breastfeeding — the reference intake is slightly higher, and intake at the reference level is appropriate.
- You are considering high-dose riboflavin (for example the 400 mg/day migraine dose) — this is a clinical decision, not a general-wellness one.
- You take medicines and are unsure how a supplement fits in — your pharmacist can check.
Common side effects: Yellow urine (harmless). No common side-effect profile at oral supplement doses.
Pregnancy and breastfeeding
The UK reference intake for riboflavin rises modestly in pregnancy (to 1.4 mg/day, UK COMA). Intake at the reference level from food or a standard supplement is appropriate. As with any supplement, talk to your pharmacist, GP, or midwife before starting, and do not use the high-dose migraine regimen in pregnancy without specialist advice.
The UK reference intake rises to 1.6 mg/day while breastfeeding (UK COMA); intake at the reference level is appropriate.
Talk to your GP, midwife, or pharmacist before starting any supplement during pregnancy or breastfeeding.
More clinical detail (for clinicians and informed readers)
Contraindications
- Known riboflavin hypersensitivity (rare).
Drug interactions
- Photodynamic / phototherapy treatments — riboflavin is light-sensitive; tell the treating clinician about any supplement.
- Tetracycline antibiotics — taken together, absorption of each may be modestly reduced; clinical relevance is limited, but separating doses is sensible.
This is not an exhaustive list. Always tell your prescriber and pharmacist about every supplement you take.
Common side effects
- Bright-yellow urine — harmless.
- Generally well tolerated.
Rare side effects
- Photosensitivity-type skin reactions — occasional case reports at high chronic doses.
How to take it
- UK Reference Nutrient Intake
- Typical supplemental range
- Everyday supplement doses are commonly 1.4-10 mg/day (around 100-700% NRV). The migraine-prevention trial dose is 400 mg/day, used under clinical supervision.
- Timing
- No specific timing requirement; water-soluble.
How to spot quality
Look for
- Form named — riboflavin or riboflavin-5-phosphate.
- NRV percentage stated (1.4 mg = 100% NRV).
- GMP-certified manufacture.
Red flags
- Generic "vitamin B2" with no form named.
- Marketing that implies migraine treatment without a GP or neurology context.
- A 400 mg "migraine" product presented as a general daily supplement rather than a supervised use.
Where Camden lands · meets the bar
Camden Medicals does not currently sell a standalone riboflavin product. Riboflavin appears as an adjunct in two multi-active B-vitamin products Camden is evaluating — a daily B-complex (1.6 mg/cap, 114% NRV, claim-eligible) and a Ginkgo B+ blend (1.4 mg/cap, 100% NRV). Both clear the look-for bar. The 400 mg migraine-prevention dose is a separate, specialist-supervised use that is not relevant to a general supplement and is not something Camden positions a product around.
Commonly combined with
Other ingredients that share a biological pathway, cofactor relationship, or evidence-backed protocol with this one. Mechanisms below cite primary physiology — not folk pairing. Doses are literature ranges, not recommendations. Talk to your pharmacist or GP before changing your stack, especially if you take prescription medication.
Vitamin B6
Moderate evidenceB-complex cluster — B2 + B6 energy-metabolism and nervous-system support.
B2 (riboflavin) provides the FAD/FMN cofactors; B6 (as PLP) is a cofactor for amino-acid metabolism. Riboflavin (FMN) is also needed to activate B6. Mechanism complementary across redox and amino-acid axes.
Evidence: Both hold UK Article 13.1 authorised claims for the nervous system and energy metabolism. [3]
Doses studied: 1.4 mg B2 + 1.4 mg B6 daily (around the UK reference intakes).
Iron
Moderate evidenceIron-metabolism pairing — B2 holds an authorised claim for normal iron metabolism (UK Article 13.1).
Riboflavin status influences iron handling and mobilisation; iron is the substrate. The UK Article 13.1 riboflavin claim covers normal metabolism of iron.
Evidence: UK Article 13.1 riboflavin "normal metabolism of iron" claim authorised. [3]
Doses studied: 1.4 mg B2 + 14 mg iron daily (around the UK reference intakes).
Found in Camden: Iron & Vitamin C Gummies 7mg 150 Gummies
Magnesium
Moderate evidenceEnergy-metabolism pairing — both hold UK Article 13.1 claims for normal energy-yielding metabolism.
Riboflavin provides redox cofactors; magnesium is a cofactor for ATP-dependent reactions. Mechanism complementary in energy metabolism.
Evidence: Both hold UK Article 13.1 authorised claims for normal energy-yielding metabolism. [3]
Doses studied: 1.4 mg B2 + 200-400 mg magnesium daily.
Found in Camden: Aurifera™ Magnesium Complex 120 Capsules