Also known as: Vitamin B12 or Cobalamin, Folic Acid, RBC folate.
B12 and folate belong to the B complex of vitamins.
The body needs folic acid to make red blood cells (RBC), white blood cells (WBC), platelets, new genetic material (DNA) in cells, and for normal growth. Folic acid also is important for the normal development of a baby (fetus).
Folate is found in green vegetables, citrus fruits, dry beans and peas, liver, and yeast
B12 is found red meat, fish, poultry, milk, and eggs.
Both B12 and folate are needed for RBC formation, cellular reparation, and DNA synthesis.
A deficiency in either B12 or folate can lead to megaloblastic anemia. This disease is characterized by the production of fewer, but larger, RBCs called macrocytes. Macrocytes have a shorter life than normal RBCs and lead to fatigue, weakness, and other symptoms of anemia.
A lack of B12 can also lead to neuropathy and nerve damage afecting hands and feet. Folate deficiency during early pregnancy can increase the risk of neural tube defects such as spina bifida in the fetus.
Its concentration is measured by means of analysis of a blood sample drawn from the vein in the arm.
Purpose of the test
To measure the Folate level in blood to help diagnose the cause of anemia or neuropathy. Also to evaluate nutritional status in some patients or to check effectiveness of treatment for B12 or folate deficiency.
These tests measure the concentration of folate and vitamin B12 in the liquid portion of the blood (serum) or inside the red blood cell (RBC). It will normally be at a higher concentration inside the cells than in the serum Either a serum or RBC folate test may be used to help detect a deficiency.
B12 and folate tests are done when a CBC, done routinely or as part of an evaluation of anemia symptoms, indicates the presence of large RBCs.
When a person shows mental or behavioral changes such as irritability, confusion, depression, and/or paranoia, B12 and folate may be done to help diagnose the underlying cause. These tests are also be ordered when a patient has physical symptoms that suggest a B12 or folate deficiency, including dizziness, weakness, fatigue, or a sore mouth or tongue.
When a patient has symptoms suggesting nerve damage such as, tingling, burning, or numbness in their hands, arms, legs, and or/feet, a B12 test may be requested.
In patients with known B12 and folate deficiencies, these tests may be ordered occasionally to help monitor the effectiveness of treatment with supplements (or with B12 injections). Normal or elevated results indicate a response to treatment.
Reference range values
1123 – 3345 nmol/L
High levels of B12 and folate are not usual. They can be seen in conditions such as leukemia or liver dysfunction. High folate levels may be seen with pernicious anemia and with vegetarian diets.
Some drugs can decrease B12 and folic acid levels including oral contraceptives, estrogens, alcohol, and some antibiotics.
B12 and/or folate deficiencies can be caused by:
• Insufficient intake. Very rare. Cases appear among vegetarians.
• Malabsorption, due to:
o Celiac disease
o Bacterial overgrowth in the stomach and intestines
o Reduced stomach acid production
o Pernicious anemia. This is the most common cause of B12 deficiency.
o Surgery that removes part of the stomach or the intestines may greatly decrease absorption.
• Increased loss, due to:
o Liver and kidney disease
o Anti-seizure medications such as phenytoin, metformin and methotrexate
• Increased need due to pregnancy.