Folate (Vitamin B9)

The normal reference range for Folate (Vitamin B9) is Serum folate above about 7 nmol/L is generally adequate; below that suggests deficiency. Serum folate reflects recent intake, so a red-cell folate test gives a better picture of longer-term stores. Since mandatory folic acid fortification of bread flour in Australia (2009), frank deficiency has become less common.. Reference ranges may vary between laboratories, so always consult your healthcare provider for interpretation.

Critical for pregnancy, red blood cell formation, and methylation processes throughout the body.

High folate is almost always due to supplementation or fortified foods and is not harmful in itself. The important caveat is that high folate can mask the blood changes of vitamin B12 deficiency while allowing the neurological damage of B12 deficiency to progress unchecked, which is why B12 is checked alongside it.

Low folate causes a macrocytic (large red cell) anaemia and, crucially in pregnancy, increases the risk of neural tube defects in the baby. Causes include poor dietary intake (few leafy greens), excess alcohol, malabsorption (coeliac disease), increased demand in pregnancy, and certain medications such as methotrexate, sulfasalazine and some anticonvulsants.

Folate is checked when investigating macrocytic anaemia or unexplained fatigue, and is part of preconception and pregnancy care (all women planning pregnancy are advised to take folic acid). It is almost always tested with vitamin B12. Routine repeat testing is unnecessary once a cause is treated.