Vitamin B12 and Folate Test

This is a test used to help diagnose the cause of anemia or neuropathy (nerve damage), to evaluate nutritional status in some patients, or 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 ; it will normally be at a higher concentration inside the cell than in the serum.

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.

PREPARATION FOR TEST

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

NORMAL FINDINGS

160-950 pg/mL or 118-701 pmol/L (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.

Reference values are dependent on many factors, including patient age, gender, sample population, and testing method. Numeric test results have different meanings in different labs. Your lab report should include the specific reference range for your test.

If there is a decreased concentration of B12 and/or folate, then it is likely there is some degree of deficiency. The test results will indicate the presence of the deficiency, but they do not necessarily reflect the severity of the anemia or neuropathy associated with the deficiency or its underlying cause. There are a variety of causes of B12 and/or folate deficiencies. Most of these are from poor intake, not absorbing the vitamins or losing more vitamins than are taken in.

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.