The main circulating forms of vitamin B₂ are riboflavin and its two cofactors flavin adenine mononucleotide (FAM) and flavin dinucleotide (FAD). These two forms are detectable in both plasma and blood cells, however, the predominant form is FAD found in red blood cells. FDP and FAM act as coenzymes in oxidation-reduction reactions and in the respiratory chain (eg. cytochrome, glutathione reductase, glutathione peroxidase, and xanthine oxidase, methylene tetrahydrofolate reductase).

Specific vitamin B₂ deficiency is very rare; it usually occurs in combination with other water soluble vitamin deficiencies, most commonly in alcoholics as a result of inadequate nutrition. Symptoms of deficiency are sore throat, inflammation of mouth, tongue and throat, cracks in lips and corners of mouth, normocytic normochromic anaemia, and dermatitis.

Vitamin B₂ is essentially non-toxic.

Plasma vitamin B₂ is bound to albumin and so concentrations fall during the acute phase response. Work in our laboratory has shown that the red cell concentration is unaffected by acute phase response and so we recommend it is measured in red cells.

Sample Requirements and Reference Ranges for Vitamin B₂

* This is the absolute minimum volume; these volumes are insufficient to carry out a repeat analysis in the event of an analytical problem.

** Please contact the Laboratory if vitamin B₂ in whole blood is required.