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Vitamin B12 level
Cobalamin test; Pernicious anemia - vitamin B12 level
The vitamin B12 level is a blood test that measures how much vitamin B12 is in your blood.
Vitamin B12
Vitamin B12 is a water-soluble vitamin. Water-soluble vitamins dissolve in water. After the body uses these vitamins, leftover amounts leave the bo...
How the Test is Performed
A blood sample is needed.
Blood sample
Venipuncture is the collection of blood from a vein. It is most often done for laboratory testing.
How to Prepare for the Test
You should not eat or drink for about 6 to 8 hours before the test.
Certain medicines may affect the results of this test. Your health care provider will tell you if you need to stop taking any medicines. DO NOT stop any medicine before talking to your provider.
Medicines that can affect the test result include:
- Colchicine
- Neomycin
- Para-aminosalicylic acid
- Phenytoin
How the Test will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why the Test is Performed
This test is most often done when other blood tests suggest a condition called megaloblastic anemia. 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.
Pernicious anemia
Anemia is a condition in which the body does not have enough healthy red blood cells. Red blood cells provide oxygen to body tissues. There are man...
Your provider may also recommend a vitamin B12 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 include:
-
Sudden severe confusion (
delirium
)
Delirium
Delirium is sudden severe confusion due to rapid changes in brain function that occur with physical or mental illness.
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Loss of brain function (
dementia
)
Dementia
Dementia is a loss of brain function that occurs with certain diseases. It affects memory, thinking, language, judgment, and behavior.
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Dementia due to metabolic causes
Dementia due to metabolic causes
Dementia is loss of brain function that occurs with certain diseases. Dementia due to metabolic causes is a loss of brain function that can occur wit...
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Normal Results
Normal values are 200 to 900 picograms per milliliter (pg/mL).
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different samples. Talk to your provider about what your specific test results mean.
What Abnormal Results Mean
Values of less than 200 pg/mL are a possible 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. Deficiency should be confirmed by checking the level of a substance in the blood called methylmalonic acid. A high level indicates a true B12 deficiency.
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
)
Malabsorption
Malabsorption involves problems with the body's ability to take in nutrients from food.
Read Article Now Book Mark ArticleCeliac disease
Celiac disease is a condition caused by damage to the lining of the small intestine. This damage comes from a reaction to eating gluten. This is a ...
Read Article Now Book Mark ArticleCrohn disease
Crohn disease is a disease where parts of the digestive tract become inflamed. It most often involves the lower end of the small intestine and the be...
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Lack of
intrinsic factor
, a protein that helps the intestine absorb vitamin B12
Intrinsic factor
Intrinsic factor is a protein that helps your intestines absorb vitamin B12. It is made by cells in the stomach lining.
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Above normal heat production (for example, with
hyperthyroidism
)
Hyperthyroidism
Hyperthyroidism is a condition in which the thyroid gland makes too much thyroid hormone. The condition is often called overactive thyroid.
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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
)
Cirrhosis
Cirrhosis is scarring of the liver and poor liver function. It is the last stage of chronic liver disease.
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Myeloproliferative disorders
(for example, polycythemia vera and chronic
myelogenous leukemia
)
Myeloproliferative disorders
Polycythemia vera is a bone marrow disease that leads to an abnormal increase in the number of blood cells. The red blood cells are mostly affected....
Read Article Now Book Mark ArticleMyelogenous leukemia
Chronic myelogenous leukemia (CML) is cancer that starts inside bone marrow. This is the soft tissue in the center of bones that helps form all bloo...
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Risks
There is very little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight, but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood buildup under the skin)
- Infection (a slight risk any time the skin is broken)
References
Drage MG, Kutok JL. Folate and B12 (cobalamin) deficiency. In: Aster JC, Pozdnyakova O, Kutok JL, eds. Hematopathology . Philadelphia, PA: Elsevier Saunders; 2013:20-21.
Mason JB. Vitamins, trace minerals, and other micronutrients. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine . 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 218.
Review Date: 2/11/2016
Reviewed By: Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
