Riboflavin
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Riboflavin
1.4mg, which is exactly 100% of the reference intake — and the reason B-vitamin supplements can turn urine bright yellow, which is harmless.
Femme Flora contains 1.4mg of riboflavin, which is 100% of the Nutrient Reference Value. Riboflavin is vitamin B2, a water-soluble vitamin found in milk, eggs, almonds and fortified cereals. It carries nine authorised health claims in Great Britain, including that riboflavin contributes to the maintenance of normal mucous membranes. It is also the reason B-vitamin supplements turn urine bright yellow — harmless, expected, and covered in section 3.
How we grade this one
Vitamins and minerals are not graded A to E. They sit on the other track: a health claim for them has either been through formal scientific assessment or it has not. That is a different question from how many trials exist.
Riboflavin carries nine health claims that have passed scientific assessment. It is in Femme Flora because it does ordinary and useful things, and not because it has anything to do with what the product is bought for. This page is careful about that distinction, because the temptation to blur it is the main compliance risk in this category.
1 · What is in the capsule
| Amount | % NRV | Also called | |
|---|---|---|---|
| Riboflavin | 1.4 mg | 100% | Vitamin B2 |
100% of the reference intake, and no more. Riboflavin is not an ingredient where a larger number buys anything, and section 4 explains why the body simply discards the excess.
2 · What riboflavin is
Riboflavin is vitamin B2, one of the water-soluble B vitamins. The body cannot make it and does not store it in any quantity, so intake comes from food, day to day.
It is widespread in ordinary food — milk and dairy, eggs, almonds, mushrooms, lean meat and fortified breakfast cereals are among the common sources. Deficiency is uncommon in the UK in people eating a varied diet.
It is also unusually sensitive to light. Riboflavin degrades on exposure, which is the reason milk was historically sold in opaque or tinted containers and why B-vitamin products are not packaged in clear glass. Ours sits in capsules inside a white bottle.
3 · The yellow urine
The most-searched question about any B vitamin, and the easiest to answer honestly.
Riboflavin is bright yellow. The name comes from flavus, the Latin for yellow. What the body does not use is cleared by the kidneys, and it takes its colour with it.
So a few hours after taking a B-vitamin supplement, urine can turn a vivid, almost fluorescent yellow. It is harmless, it is expected, and it is not a sign that the supplement is not working or that anything is wrong. It happens at ordinary intakes and it happens more obviously at large ones.
It is worth knowing in advance rather than discovering at 11pm. If the colour persists for days after you stop taking a supplement, or comes with pain or other symptoms, that is a different matter and worth a word with your GP or pharmacist.
4 · Why 100% and not more
Riboflavin absorption is limited by a transport system that saturates at modest intakes. Past roughly the amount a normal meal provides, the proportion absorbed falls away, and what is absorbed beyond the body’s working requirement is cleared promptly.
A supplement carrying many times the reference intake therefore produces a brighter colour rather than a proportionally larger effect. We carry 100%, which meets the reference intake in full and clears the threshold for all nine claims with room to spare.
5 · The nine claims
Reproduced exactly as written. We do not reword them and we do not add to them.
- 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 skin
- Riboflavin contributes to the maintenance of normal red blood cells
- 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
They apply from a threshold of 15% of the reference intake. We carry 100%.
What we do not claim
- We do not claim riboflavin does anything for vaginal or intimate health. No such claim exists for it, and we are not going to imply one by placing an unrelated claim next to intimate-health copy.
- We do not claim those nine sentences describe what this product does. They describe what the nutrient contributes to, assessed on the nutrient and not on our formulation.
- We do not claim the yellow colour indicates absorption, potency or effect. It indicates that riboflavin is yellow.
- We do not claim this product treats, prevents or reduces the risk of anything.
What we claim is the composition: 1.4mg of riboflavin, 100% of the Nutrient Reference Value.
Worth knowing
Riboflavin is well tolerated and has no established upper intake level, because excess is cleared rather than accumulated. If you take a multivitamin or a B-complex alongside this product, you will be taking more than 100% of the reference intake — which is not a concern, but it does explain a brighter colour. If you are managing a condition or taking medication, speak to your GP or pharmacist before adding a supplement.
Common questions
- How much riboflavin is in Femme Flora?
- 1.4mg per daily serving, which is exactly 100% of the Nutrient Reference Value. The threshold at which the health claims apply is 15% of the reference intake, so the dose clears it with a good deal of room to spare.
- Why does a B vitamin turn your urine bright yellow?
- Riboflavin is itself bright yellow — the name comes from the Latin for yellow. What the body does not use is cleared by the kidneys and takes its colour with it. It is harmless and expected, and it is not a sign that anything is wrong.
- Is riboflavin the same as vitamin B2?
- Yes. Riboflavin is the nutrient name used on the GB register and on our label; vitamin B2 is the everyday name for the same thing. Both refer to the same water-soluble vitamin, which the body cannot make and does not store in quantity.
- Why only 1.4mg when other supplements have much more?
- Riboflavin absorption saturates at modest intakes. Past roughly what a normal meal supplies, less of it is absorbed and what is absorbed beyond requirement is cleared quickly. A much larger dose produces a brighter colour rather than a proportionally larger effect.
- Where else do you get riboflavin?
- Milk and dairy, eggs, almonds, mushrooms, lean meat and fortified breakfast cereals are all common sources. Deficiency is uncommon in the UK in people eating a varied diet. Riboflavin also degrades in light, which is why B vitamins are not sold in clear packaging.
Sources
- GB Nutrition and Health Claims Register. Checked against the register export of 19 May 2026. Nine authorised claims for riboflavin, listed on the register under Riboflavin (Vitamin B2) and reproduced above verbatim. Condition of use: the food must be at least a source of riboflavin, meaning 15% of the Nutrient Reference Value per daily portion.
- Retained Commission Regulation (EU) No 432/2012, establishing the list of permitted health claims. The wordings above and the 15% NRV condition originate here.