Riboflavin – Vitamin B2

foods high in vitamin B2, including milk yogurt eggs salmon organ meats cheese spinach beans mushrooms

Vitamin B2, or riboflavin, is naturally present in foods, added to foods, and available as a supplement. Bacteria in the gut can produce small amounts of riboflavin, but not enough to meet dietary needs. Riboflavin is a key component of coenzymes involved with the growth of cells, energy production, and the breakdown of fats, steroids, and medications. [1] Most riboflavin is used immediately and not stored in the body, so excess amounts are excreted in the urine. [2] An excess of dietary riboflavin, usually from supplements, can cause urine to become bright yellow.

Recommended Amounts

RDA: The Recommended Dietary Allowance (RDA) for men and women ages 19+ years is 1.3 mg and 1.1 mg daily, respectively. For pregnancy and lactation, the amount increases to 1.4 mg and 1.6 mg daily, respectively.

UL: A Tolerable Upper Intake Level (UL) is the maximum daily dose unlikely to cause adverse side effects in the general population. A UL has not been established for riboflavin, because a toxic level has not been observed from food sources or from longer-term intakes of high-dose supplements.

Vitamin B2 and Health

Because riboflavin assists many enzymes with various daily functions throughout the body, a deficiency can lead to health problems. Animal studies show that the brain and heart disorders and some cancers can develop from long-term riboflavin deficiency.

Food Sources

Riboflavin is found mostly in meat and fortified foods but also in some nuts and green vegetables.

Signs of Deficiency and Toxicity


A riboflavin deficiency is very rare in the United States. Disorders of the thyroid can increase the risk of a deficiency. A riboflavin deficiency most often occurs with other nutrient deficiencies, such as in those who are malnourished. Symptoms may include:

  • Cracked lips
  • Sore throat
  • Swelling of the mouth and throat
  • Swollen tongue (glossitis)
  • Hair loss
  • Skin rash
  • Anemia
  • Itchy red eyes
  • Cataracts in severe cases

Groups at higher risk of deficiency:

  • Vegans/vegetarians due to a lower intake or complete exclusion of dairy and meat products.
  • Pregnant women, especially in those who consume little dairy (lactose intolerance) or meat, due to increased nutrient needs with a growing fetus.


A toxic level of riboflavin has not been observed from food sources and supplements. The gut can only absorb a limited amount of riboflavin at one time, and an excess is quickly excreted in the urine. [2] Therefore, a Tolerable Upper Intake Level for riboflavin has not been established.

Did You Know?

Ever wonder why you don’t usually see milk stored in glass bottles anymore? The reason is due to riboflavin. If the vitamin is exposed to too much light, it can be deactivated from its usable form. Therefore milk is now typically sold in cartons or opaque plastic containers to block light.


B Vitamins
Vitamins and Minerals

Last reviewed March 2023

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