Specimen Requirements

1 serum gel tube (1 ml of serum) OR 1 plain, red-top tube (1 mL of serum) from a fasting patient (overnight preferred). Avoid hemolysis. Centrifuge blood as soon as possible and send specimen refrigerated, or send unspun blood to laboratory within 4 hours of draw. Protect specimen from light.
Precautions:  This test should not be requested on patients who have recently received methotrexate or other folic acid antagonist.