Vitamin B12 Deficiency Test

 
The vitamin B12 deficiency test measures how much vitamin B12 is in your blood.

How to Prepare for the Test

You should not eat or drink for 6 to 8 hours before the test.

Certain medicines may affect the results of this test. Your physician will tell you if you need to stop taking any medicines. Do not stop any medicine before talking to your physician.

Medicines that can affect the test result include:

  • Colchicine
  • Neomycin
  • Para-aminosalicylic acid
  • Phenytoin

Why the Test is Performed

This test is most often done when other blood tests suggest a condition called megaloblastic anemia. (Cardio-Med's comprehensive metabolic panel can detect this condition as well as others.) Pernicious anemia is a form of megaloblastic anemia caused by poor vitamin B12 absorption. This can occur when the stomach makes less of the substance the body needs to properly absorb vitamin B12.

This vitamin deficiency test may be ordered by your Cardio-Med physician on the basis of the results of a complete physical exam.

Your physician may also order a vitamin B12 deficiency test if you have certain nervous system symptoms. A low level of B12 can cause numbness or tingling in the arms and legs, weakness, and loss of balance.

Other conditions for which the test may be done:

  • Sudden severe confusion (delirium)
  • Loss of brain function (dementia)
  • Dementia due to metabolic causes

Normal Results

Normal values are 200 - 900 picograms per milliliter (pg/mL).

Talk to your physician about what your specific test results mean.

What Abnormal Results Mean

Values of less than 200 pg/mL are a sign of a vitamin B12 deficiency. People with this deficiency are likely to have or develop symptoms. Older adults with vitamin B12 levels between 200 and 500 pg/mL may also have symptoms.

Causes of vitamin B12 deficiency include:

  • Not enough vitamin B12 in diet (rare, except with a strict vegetarian diet)
  • Diseases that cause malabsorption (for example, celiac disease and Crohn disease)
  • Lack of intrinsic factor, a protein that helps the intestine absorb vitamin B12
  • Above normal heat production (for example, with hyperthyroidism)
  • Pregnancy

A Schilling test can find the cause of a vitamin B12 deficiency.

An increased vitamin B12 level is uncommon. Usually, excess vitamin B12 is removed in the urine.

Conditions that can increase B12 level include:

  • Liver disease (such as cirrhosis or hepatitis)
  • Chronic myelocytic leukemia


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Adapted from the U.S. National Library of Medicine, National Institutes of Health