Vitamin B12 and Folate, Vitamin B12, Cobalamin

This is a blood test used to determine the cause of anemia or neuropathy (nerve damage). It is also used to check nutritional status in some patients. It is also used to monitor effectiveness of treatment for B12 or folate deficiency. These tests measure the concentration of folate and vitamin B12 in the serum (liquid portion of the blood). The amount of folate inside the red blood cell (RBC) may also be measured. B12 and folate are both part of the B complex of vitamins and come from food. Folate is found in leafy green vegetables, citrus fruits, dry beans and peas, liver, and yeast; while B12 is found in animal products such as red meat, fish, poultry, milk, and eggs. Fortified cereals, breads, and other grain products are now also important dietary sources of both B12 and folate (identified as "folic acid" on nutritional labels), especially for those vegetarians who do not consume any animal products.

Both B12 and folate are necessary for normal RBC formation, tissue and cellular repair, and DNA synthesis. B12 is also important for nerve health, while folate is necessary for cell division such as is seen in a fetus during pregnancy. A deficiency in either B12 or folate can lead to a form of anemia characterized by the production of fewer, but larger, RBC's (called macrocytes). A deficiency in B12 can also result in varying degrees of neuropathy, nerve damage that can cause tingling and numbness in the patient's hands and feet. A deficiency in folate can cause neural tube defects such as spina bifida in a growing fetus.

If a patient is deficient in both B12 and folate, but only takes folic acid supplements, the B12 deficiency may be masked. The anemia associated with both may be resolved, but the underlying neuropathy (nerve damage) will persist.

The Schilling test was once ordered fairly routinely to confirm a diagnosis of pernicious anemia as the cause of a B12 deficiency. It is still ordered occasionally but has fallen from favor because it involves the administration of radioactive B12. The Schilling test has been replaced, in part, by the measurement of intrinsic factor binding antibodies and parietal cell antibodies.

PREPARATION FOR TEST

A blood sample is obtained by inserting a needle into a vein in the arm. No special preparation is necessary.

NORMAL FINDINGS

160-050 pg/mL (SI units)

Ranges for normal findings may vary among different laboratories and hospitals. You should always check with your doctor after having lab work or other tests done to discuss the meaning of your test results and whether your values are considered within normal limits.

MEANING OF TEST

Your caregiver will go over the test results with you and discuss the importance and meaning of your results, as well as treatment options and the need for additional tests if necessary.

OBTAINING THE TEST RESULTS

It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results.