Folate (whole blood/red cells)

Folates (vitamin B9) serve as cofactors in the enzymatic transfer of single carbon units in a variety of metabolic pathways. Folates are necessary for nucleic acid and mitochondrial protein synthesis, amino acid metabolism, and other cellular processes that involve single carbon transfers. Folate deficiency can be caused by low dietary intake, malabsorption due to gastrointestinal diseases, inadequate utilization due to enzyme deficiencies of folate antagonist therapy, drugs, and excessive folate demand, such as during pregnancy. Low serum folate levels reflect the first stage of folate negative balance, and can precede tissue depletion. Low red-blood cell folate (whole blood) values reflect the second stage of negative folate balance, and more closely correlate with tissue levels and megaloblastic anaemia.