Test Details: Vitamin B2, also called riboflavin, is important for energy production, enzyme function, and normal fatty acid and amino acid synthesis. It is also necessary for the reproduction of the antioxidant glutathione. Vitamin B2 is water-soluble like the reset of the B vitamins. It is not stored in ample amounts and excess is typically lost through urination, causing bright yellow urine, meaning a constant supply of vitamin B2 is needed. Deficiency in this vitamin is usually part of a multiple-nutrient deficiency and does not occur in isolation.