EBM Consult

Lab Test: Folate (Serum) Level

    Lab Test
    • Folate (serum)
    • This test quantifies the folate level in the blood.  It is used in patients who have megaloblastic anemia. 
    • Used to assess nutritional status, especially in alcoholics.
    Reference Range
    • 5-25 mg/mL or 11-57 nmol/L (SI units)
    Indications & Uses
    • Folate availability in pregnancy
    • Evaluation of hemolytic disorders
    • Anemia caused by folic acid deficiency - RBCs are abnormally large, causing a megaloblastic anemia. 
    • Workup in alcoholic patients - to assess nutritional status.
    Clinical Application
    • Folic acid is needed for the adequate synthesis of certain purines and pyrimidines, which are precursors of deoxyribonucleic acid (DNA) needed for normal RBC and WBC production and function. 
    • It is also used in the synthesis of several amino acids. 
    • It is necessary for conversion of inactive 5-methyltetrahydrofolate to the active tetrahydrofolate, the active form of folate.  The folate level depends on adequate dietary ingestion and normal intestinal absorption of this vitamin. 
    • The finding of a low serum folate means that the patient's recent diet has been subnormal in folate content and/or that recent absorption of folate has been subnormal.  In time, folate levels will also drop in the tissues.  It is advisable to determine RBC folate in addition to serum folate. 
    • Increased levels may indicate:
      • Pernicious anemia, vegetarianism, or recent massive blood transfusion
    • Decreased levels may indicate:
      • Malnutrition, malabsorption syndrome (e.g., sprue, celiac disease), pregnancy, folic acid deficiency (megaloblastic) anemia, hemolytic anemia, malignancy, liver disease, chronic renal disease.
    Related Tests
    • Vitamin B12 - this is a measurement of the level of vitamin B12 in the serum and should be performed with a folic acid test.
    • Complete blood cell count (CBC) - this is performed routinely and can identify megaloblastic anemia.
    Drug-Lab Interactions
    • A folate-deficient patient who has received a blood transfusion may have a falsely normal result. 
    • Because RIA is the method of choice for folic acid determination, radionuclide administration should b e avoided for at least 24 hours.
    • Drugs that may cause decreased folic acid levels include:  alcohol, aminopterin, aminosalicylic acid, ampicillin, antimalarials, chloramphenicol, erythromycin, estrogens, methotrexate, oral contraceptives, penicillin derivatives, phenobarbital, phenytoin, and tetracyclines.
    Test Tube Needed
    • Red top tube
    • Draw the specimen before starting folate therapy.
    • Collect a venous blood sample.
    • Avoid hemolysis.  Folate in the RBCs can falsely raise serum folate levels when hemolysis of the RBC occurs. 
    • Indicate on the laboratory slip any medications that may affect test results. 
    • Apply pressure or a pressure dressing to the venipuncture site and assess the site for bleeding.
    Storage and Handling
    • Transport the blood to the laboratory immediately after collection.
    What To Tell Patient Before & After
    • Explain the procedure to the patient. 
    • Tell the patient that no fasting is usually required.  (However, some laboratories prefer an 8-hour fast.)
    • Instruct the patient not to consume alcoholic beverages before the test.
    • Pagana K, Pagana TJ eds. Mosby's Manual of Diagnostic and Laboratory Tests. 5th Ed.  St. Louis, Missouri. 2014

MESH Terms & Keywords

  • Folate