Vitamin B12 Test

This test measures the level of vitamin B12 in the blood.

This test measures the level of vitamin B12 in the blood.

This test measures the level of vitamin B12 in your blood. Vitamin B12 is often ordered with the blood folate test. Vitamin B12 and folate are two vitamins that cannot be produced in the body and must be supplied by the diet. The body needs these two vitamins to:

  • Make normal red blood cells (RBC)
  • Repair tissues and cells in the body
  • Make DNA, the genetic material in cells
  • Maintain proper nerve function

In certain anemias, such as the condition called pernicious anemia, the body does not absorb enough vitamin B12. The resulting deficiency interferes with the body's ability to produce an adequate amount of red blood cells. Vitamin B12 is not present in any plants, fruits or vegetables. Therefore, the odds of developing a vitamin B12 deficiency increase with a restricted diet that lacks animal protein foods, such as a strict vegan diet. However, it may take years to decrease the vitamin B12 stores in the body to an abnormally low level.

Vitamin B12 testing may be recommended if you have symptoms of a vitamin 12 deficiency, such as:

  • Tingling, numbness and/or burning in the feet, hands, arms and legs
  • Confusion, forgetfulness or paranoia
  • Diarrhea and loss of appetite
  • Dizziness, fatigue and muscle weakness
  • Pale skin
  • Rapid or irregular heart rate
  • Shortness of breath
  • Sore tongue and mouth

Most people who have symptoms due to B12 and/or folate deficiency will also have anemia. However, sometimes a deficiency with symptoms is present without anemia. B12 testing may be recommended if you have a history of vitamin B12 deficiency, malnutrition or problem absorbing nutrients from your food.

The blood sample is usually taken by placing a needle in a vein in the arm or by pricking a finger.

  • You may need to fast (not eat) for a few hours before the test. Ask your healthcare provider if there are any specific instructions you need to follow before the test.
  • Ask your healthcare provider if you need to stop taking any medicines before the test.
  • Do not stop taking any medicine unless your healthcare provider tells you to do so.

This care path's costs do not include the charge to draw blood from a vein (venipuncture). There will only be one charge to draw blood, even if multiple tests are being performed on the samples that are taken.

What should I ask my healthcare provider before having this test?

  • Is there any special preparation for the test? (If so, get clear instructions on what you need to do.)
  • What is the reason for the test? Will the test results change my treatment plan? If not, do I need the test?


Also known as:

Vitamin B12 Test
Laboratory Work
Pernicious Anemia
Vitamin B12 Blood Test
Blood Test for Vitamin B12
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