Folate refers to all derivatives of folic acid. Folate is an essential vitamin present in a wide variety of foods such as dark leafy vegetables, citrus fruits, yeast, beans, eggs, and milk. Folate is vital to normal cell growth and DNA synthesis. A folate deficiency can lead to megaloblastic anemia and ultimately to severe neurologic problems. Folate levels in both serum and RBCs are used to assess folate status. The serum folate level is an indicator of recent folate intake. RBC folate is the best indicator of long-term folate stores. A low RBC folate value may indicate a prolonged folate deficiency. Other names: vitamin B9.
Normal range:
Serum folate: >6.5 ng/mL
RBC folate: 280 " “903 ng/mL
Use
Evaluation of folate deficiency
Interpretation
Increased In
Blind loop syndrome
Vegetarian diet
Distal and small bowel disease
PA
Decreased In
Untreated folate deficiency, associated with megaloblastic anemia
Infantile hyperthyroidism
Alcoholism
Malnutrition
Scurvy
Liver disease
Vitamin B12 deficiency
Dietary amino acid excess
Chronic hemodialysis
Celiac disease
Disorders of glutathione metabolism
Sideroblastic anemia
Pregnancy
Whipple disease
Amyloidosis
Limitations
Serum folate is a relatively nonspecific test. Low serum folate levels may be seen in the absence of deficiency, and normal levels may be seen in patients with macrocytic anemia, dementia, neuropsychiatric disorders, and pregnancy disorders.
Patients with low RBC folate or megaloblastic anemia should be evaluated for vitamin B12 deficiency. To distinguish between vitamin B12 and folate deficiency, determination of homocysteine (HCS) and methylmalonic acid (MMA) will help. In vitamin B12 deficiency, both HCS and MMA are elevated, whereas in folate deficiency, only HCS levels are elevated.