The normal amount present in blood is 3.6 to 20 µg/L (7 to 40 nmol/L), while in red blood cells the normal range is 225 to 800 µg/L. The test is normally done as part of the investigation of anaemia.
The recommended daily total folate dietary intake is 50 µg. in infants, 100 µg. in children and 200 µg. in adults.
Low levels may be present in:
- the elderly and infancy,
- poor diet,
- pregnancy and breastfeeding,
- scurvy (lack of vitamin C),
- kwashiorkor (protein starvation),
- tropical sprue,
- coeliac disease,
- malabsorption syndromes,
- Crohn disease,
- partial removal of stomach,
- heart failure,
- blood infection (septicaemia),
- Whipple’s disease,
- chronic haemolytic anaemias,
- multiple myeloma,
- Tuberculosis (TB),
- haemodialysis for kidney failure,
- active liver disease,
- premature babies and with some drugs (e.g. barbiturates, oral contraceptive, trimethoprim, tetracyclines, nitrofurantoin, primidone, methotrexate)
A false low blood level may occur with severe vitamin B12 deficiency, while a false normal level may follow a blood transfusion.
Blood folate levels reflect folate absorption from the diet in the past week only. Red blood cell folate is a more accurate measure of total body folate levels and is less affected by diet than blood folate levels. Folate is stored mainly in the liver.