Vitamin B12 levelCobalamin 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 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.
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:
- Para-aminosalicylic acid
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.
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)
- Loss of brain function (dementia)
- Dementia due to metabolic causes
- Nerve abnormalities, such as peripheral neuropathy
Normal values are 160 to 950 picograms per milliliter (pg/mL), or 118 to 701 picomole per liter (pmol/L).
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 160 pg/mL (118 pmol/L) are a possible sign of a vitamin B12 deficiency. People with this deficiency are likely to have or develop symptoms.
Older adults with a vitamin B12 level less than 100 pg/mL (74 pmol/L) 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 involves problems with the body's ability to take in nutrients from food.
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 ...
- Lack of intrinsic factor, a protein that helps the intestine absorb vitamin B12
- Above normal heat production (for example, with hyperthyroidism)
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 is scarring of the liver and poor liver function. It is the last stage of chronic liver disease.
- Myeloproliferative disorders (for example, polycythemia vera and chronic myelogenous leukemia)
Polycythemia vera (PV) is a bone marrow disease that leads to an abnormal increase in the number of blood cells. The red blood cells are mostly affe...
There is 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
- Multiple punctures to locate veins
- Hematoma (blood buildup under the skin)
- Infection (a slight risk any time the skin is broken)
Chernecky CC, Berger BJ. Vitamin B 12 (cyanocobalamin, CBL, extrinsic factor) - serum. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. St Louis, MO: Elsevier Saunders; 2013:1180-1181.
Mason JB. Vitamins, trace minerals, and other micronutrients. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 218.
Review Date: 1/19/2018
Reviewed By: Richard LoCicero, MD, private practice specializing in hematology and medical oncology, Longsteet Cancer Center, Gainesville, GA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.