Riboflavin (Vitamin B2): Safety Assessment

The United Kingdom Expert Group on Vitamins and Minerals (EVM) last evaluated vitamins and minerals for safety in 2003 and set a so-called Safe Upper Level (SUL) or Guidance Level for each micronutrient, provided sufficient data were available. This SUL or Guidance Level reflects the safe maximum amount of a micronutrient that will not cause any side effects when taken daily from all sources for a lifetime.

The maximum safe daily intake for vitamin B2 is 43 mg. The maximum safe daily amount for vitamin B2 is approximately 30 times the EU recommended daily intake (Nutrient Reference Value, NRV).

This value is composed of an assumed highest intake via conventional foods of 3 mg per day and an intake via food supplements of 40 mg vitamin B2 per day, which is considered safe.

The data of the NVS II (National Nutrition Survey II, 2008) on the daily intake of vitamin B2 from all sources (conventional food and dietary supplements) indicate that an amount of 43 mg is far from being reached.

Adverse effects of excessive vitamin B2 intake from foods or supplements have not been observed.

In one study, no adverse effects occurred in 49 patients after an intake of 400 mg per day taken over three months. In two cases, mild undesirable side effects such as diarrhea and polyuria (abnormally increased urine output) occurred. Also, excessive intake of riboflavin may cause the urine to turn yellow-orange.