Folate (serum)

Folates are a class of vitamin compounds which serve as cofactors in the enzymatic transfer of single carbon units in many important metabolic pathways. They are necessary for nucleic acid and mitochondrial protein synthesis as well as amino acid metabolism. Folate must be consumed regularly. Serum folate levels indicate recent nutritional status, are frequently sufficient to diagnose folate deficiency and may reflect impaired absorption or increased losses. Impaired absorption: Coeliac disease, bacterial overgrowth in the stomach and intestines, or surgery to remove part of the stomach or the intestines, all greatly reduce absorption. Increased losses: liver and kidney disease, alcoholism, or anti-seizure medications (phenytoin can decrease folate as can drugs such as metformin and methotrexate).

Demonstrable macrocytic anaemia (as seen in red cell indices)
Investigations of suspected subacute combined degeneration of the spinal cord (a deficiency not necessarily apparent in a patient's red cell indices)

>2.7 μg/L