Vitamin B2 (Riboflavin)
The vitamin that turns your wee bright yellow. Harmless, and proof it's working.
Riboflavin is a building block for two coenzymes, FAD and FMN, that nearly every cell uses to release energy from food. It also supports red blood cell production and helps the body process other B vitamins, including B6 and folate. Absorption saturates above roughly 27mg in a single dose, so spreading intake across the day matters more than taking one large tablet. The harmless yellow urine some people notice after starting a B vitamin is riboflavin being excreted once the body has taken what it needs.
Reference values
Daily reference values from official nutrition authorities. These are population reference figures, not personal recommendations.
| RDA | Upper limit | Source |
|---|---|---|
| 1.3 mg | No UL set | UK SACN DRVs (1991) — riboflavin RNI men 1.3mg/day, women 1.1mg/day; 1.3mg/day used as general adult reference. No SACN or EFSA numerical UL established. |
| 1.3 mg | No UL set | UK SACN DRVs (1991) — riboflavin RNI men 1.3mg/day, women 1.1mg/day; 1.3mg/day used as general adult reference. No SACN or EFSA numerical UL established. |
Forms and bioavailability
Not all forms are absorbed equally. The form on your supplement label affects how much your body can actually use.
| Form | Absorption | With food | Timing | Evidence |
|---|---|---|---|---|
| Riboflavin | Typical | With food | Morning | Strong |
| Riboflavin-5-Phosphate (R5P) | Higher | With food | Morning | Informational |
Stack Almanac adds your riboflavin intake from every source you log, standalone or bundled in a multivitamin, and checks the running total against the UK reference intake.
Track your Vitamin B2 (Riboflavin) in Stack Almanac
Last reviewed: 2026-07-08. Reference values are adult-general RDAs from UK. Individual needs may vary. This page is for informational purposes only and is not a substitute for professional medical advice.