Riboflavin (vitamin B2): what it does and how much you need
Riboflavin (vitamin B2) helps turn food into energy and helps cells grow and work. Adults need 1.3 milligrams for men and 1.1 milligrams for women, and no upper limit has been set.
General information, not medical advice. Check with a doctor or pharmacist before taking a supplement, especially if you are pregnant or breastfeeding, take any medicine, or are under 18.
In the UK
In the UK, adults need 1.3 milligrams a day for men and 1.1 milligrams for women, and the NHS says up to 40 milligrams a day from supplements is unlikely to cause harm.
How much you need and the upper limit
| US (NIH) | UK (NHS) | |
|---|---|---|
| Adults need | 1.3 milligrams for men and 1.1 milligrams for women | 1.3 milligrams a day for men and 1.1 milligrams for women |
| Upper limit | No upper limit has been set for riboflavin. | Up to 40 milligrams a day from supplements |
The UK figure is the amount the NHS says is unlikely to cause harm. Figures are for adults.
Cautions
- High doses can turn urine bright yellow, which is harmless.
Food sources
- Eggs
- Lean meat
- Milk and yogurt
- Mushrooms
- Almonds
- Fortified cereals
Quick answers
- What does riboflavin (vitamin B2) do?
- Riboflavin (vitamin B2) helps turn food into energy and helps cells grow and work.
- How much riboflavin (vitamin B2) do adults need?
- Adults need 1.3 milligrams for men and 1.1 milligrams for women (US, NIH). In the UK: 1.3 milligrams a day for men and 1.1 milligrams for women (NHS).
- What is the upper limit for riboflavin (vitamin B2)?
- US: No upper limit has been set for riboflavin. UK (NHS): up to 40 milligrams a day from supplements is unlikely to cause harm.
- Which foods have riboflavin (vitamin B2)?
- Eggs, lean meat, milk and yogurt, mushrooms, almonds, fortified cereals.
- What should I watch out for with riboflavin (vitamin B2)?
- High doses can turn urine bright yellow, which is harmless.
Sources
- NIH Office of Dietary Supplements fact sheet
https://ods.od.nih.gov/factsheets/Riboflavin-HealthProfessional/ - NHS vitamins and minerals guidance
https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-b/
Ask Supplement Check yourself
Type a vitamin, mineral or supplement, a dose, or a product name, and get the daily need, the upper limit and any cautions. Open Supplement Check, free, no sign-up.
In Claude or any app that takes MCP connectors, add https://goodturn-mcp.pages.dev/supplementcheck/mcp and ask: “How much riboflavin (vitamin B2) do I need?”