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Riboflavin (Vitamin B2)

SI UNITS (recommended)


* The SI units is the recommended method of reporting clinical laboratory results

Vactochrome, lactoflavin, vitamin G
Units of measurement
nmol/L, µg/L, µg/dL, µg/100mL, µg%, ng/mL

Riboflavin (vitamin B2), or riboflavin, is one of the water-soluble vitamins. It is synthesized in plants and microorganisms and occurs naturally in three forms: the physiologically inactive riboflavin and the physiologically active coenzymes flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). The latter accounts for about 90% of the total riboflavin in whole blood. Because of their capacity to transfer electrons, FAD and FMN are essential for proton transfer in the respiratory chain, for the dehydration of fatty acids, the oxidative deamination of amino acids, and for other redox processes.

Dietary riboflavin is absorbed in the small intestine. The body stores of a well-nourished person are adequate to prevent riboflavin deficiency for 5 months. Excess riboflavin is excreted in the urine and has no known toxicity. Foods high in riboflavin include milk, liver, eggs, meat, and leafy vegetables. Riboflavin deficiency occurs with other nutritional deficiencies, alcoholism, and chronic diarrhea and malabsorption. Certain drugs antagonize the action or metabolism of riboflavin, including phenothiazine, oral contraceptives, and tricyclic antidepressants. The RDA of riboflavin is 1.3 mg/day for adult males and 1.1 mg/day for adult females. Reduced glutathione reductase activity greater than 40% is an indication of deficiency.


  • Patients with anorexia nervosa
  • Individuals who avoid dairy products (such as people with lactose intolerance) because dairy products are a good source of riboflavin
  • Patients with malabsorptive syndromes such as celiac sprue, malignancies, and short bowel syndrome
  • Rare inborn errors of metabolism in which there is a defect in riboflavin synthesis
  • Long-term use of phenobarbital and other barbiturates, which may lead to oxidation of riboflavin and impair its function
Units description
Nanomole per liter

nmol/L = nM/L = nanomol/L

Microgram per liter µg/L = mcg/L = ug/L= microg/L = microgram/L = µg/liter = mcg/liter = ug/liter
Microgram per deciliter µg/dL = mcg/dL = ug/dL= microg/dL = microgram/dL
Microgram per 100 milliliters µg/100mL = mcg/100mL = ug/100mL= microg/100mL = microgram/100mL
Microgram percent µg% = mcg% = ug%= microg% = microgram%
Nanogram per milliliter ng/mL = nanog/mL = nanogram/mL

Lab units Conversion Calculator. Convert Riboflavin (Vitamin B2) level to nmol/L, µg/L, µg/dL, µg/100mL, µg%, ng/mL
Clinical laboratory units online conversion from conventional or traditional units to Si units. Table of conversion factors for Riboflavin (Vitamin B2).