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B12 and Folate


January 13th, 2020


Folate, also known as vitamin B9, is an important coenzyme in DNA and amino acid metabolism pathways.
    • Normal Range

    • Serum folate: >9 nmol/L
    • Red cell folate: 360 - 1400 nmol/L
  • Interpretation

  • Serum folate is the total concentration of folate, and can fluctuate rapidly with changes in folate intake. In the case of poor intake the serum folate will fall acutely before true folate deficiency is present.
  • Red cell folate is a measure of the folate in tissues, and is an indicator of true folate deficiency.


Folate is a group of compounds that derive from tetrahydrofolate.
  • Absorption

  • Dietary folate is most commonly in polyglutamate forms, which in themselves are not absorbable and require cleaving by brush border enzymes prior to absorption within the jejunum.
  • Physiology
  • Transport and Storage

  • Folate is transported in plasma mainly through binding to albumin, and is mainly stored by the liver. Folate is taken up by proliferating cells.
  • Roles

  • Folate coenzymes are important for DNA metabolism and amino acid metabolism pathways. They are required for the synthesis of DNA from thymidine and purines, as well as for the synthesis of the amino acids methionine, cysteine, serine, glycine and histidine.

Folate Deficiency

  • Look For

  • Reduced serum red cell folate levels
  • Macrocytic, hyperchromic anaemia
  • Hypersegmented neutrophils
  • Manifestations

  • Megaloblastic anaemia
  • Neural tube defects (deficiency during pregnancy)
  • Increased cardiovascular risk
  • Dementia
  • Causes of Folate Deficiency

  • Nutritional deficiency - poor intake, alcohol abuse
  • Malabsorption - coeliac disease, inflammatory bowel disease, jejunal resection
  • Increased requirement - pregnancy, malignancy
  • Impaired metabolism - methotrexate, trimethoprim
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