<unk>  is diagnosed with a blood test called RBC assays (red blood cell), measured as methyltetrahydrofolate (in practice, "folate" refers to all derivatives of folic acid, but methylhydrofolate is the quasi unique form of "folate" in the blood). Homocysteine is elevated (5-MTHF is used to convert homocysteine to methionine) as in vitamin B12 deficiency, whereas methylmalonic acid is normal (elevated in vitamin B12 deficiency and vitamin B6 deficiency). More specifically, according to a 2014 UK guideline, * A serum folate level of less than 7 nmol/l (3 μg/l) is indicative of<unk> ; * Red blood cell folate testing is not routinely performed, since serum folate is sufficient in most cases, however, if there is a strong suspicion of<unk>  despite a normal serum folate level, a red cell folate test may be performed. * Plasma total homocysteine is only measured in special circumstances. A level above 15 μmol/l could be indicative of a<unk> , but local reference ranges should be taken into account.
Folate deficiency
Vitamin E deficiency
Properdin deficiency
Zinc deficiency
Hereditary folate malabsorption
Iron deficiency
Familial isolated vitamin E deficiency
Cerebral folate deficiency