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 what it needs of these vitamins, leftover amo...
Read Article Now Book Mark ArticleHow 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.
Read Article Now Book Mark ArticleHow 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 causes a form of megaloblastic anemia caused by vitamin B12 deficiency due to poor vitamin B12 absorption. This can occur when the stomach makes less of the substance (called intrinsic factor) the body needs to efficiently 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...
Read Article Now Book Mark ArticleYour 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 can occur with physical or mental illness.
Read Article Now Book Mark Article - Loss of brain function (dementia)
Dementia
Dementia is a loss of brain function that occurs with certain diseases. It affects one or more brain functions such as memory, thinking, language, j...
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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 may also be referred to as major neurocognitive disorder. Dementia du...
Read Article Now Book Mark Article - Nerve abnormalities, such as peripheral neuropathy
Peripheral neuropathy
Peripheral nerves carry information to and from the brain. They also carry signals in both directions between the spinal cord and the rest of the bo...
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Normal Results
Normal values are 160 to 950 picograms per milliliter (pg/mL), or 118 to 701 picomoles 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 degree of deficiency are likely to have or develop 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 (absorb) nutrients from food.
Read Article Now Book Mark ArticleCeliac disease
Celiac disease is an autoimmune condition that damages the lining of the small intestine. This damage comes from a reaction to eating gluten. This ...
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...
Read Article Now Book Mark Article - Lack of intrinsic factor, a protein that helps the intestine absorb vitamin B12 efficiently
Intrinsic factor
Intrinsic factor is a protein that helps your intestines absorb vitamin B12. It is made by cells in the stomach lining.
Read Article Now Book Mark Article - Above normal body 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.
Read Article Now Book Mark Article - Pregnancy
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)
Polycythemia vera
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 the most af...
Read Article Now Book Mark ArticleChronic myelogenous leukemia
Chronic myelogenous leukemia (CML) is cancer that starts inside the bone marrow. This is the soft tissue in the center of bones that helps form all ...
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Risks
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
Fainting
Fainting is a brief loss of consciousness due to a drop in blood flow to the brain. The episode most often lasts less than a couple of minutes and y...
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-
Hematoma (blood buildup under the skin)
Hematoma
A bruise is an area of skin discoloration. A bruise occurs when small blood vessels break and leak their contents into the soft tissue beneath the s...
Read Article Now Book Mark Article - Infection (a slight risk any time the skin is broken)
Reviewed By
Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. Editorial update 08/19/2024.
Marcogliese AN, Hensch L. Resources for the hematologist: interpretive comments and selected reference values for neonatal, pediatric, and adult populations. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 159.
Mason JB, Booth SL. Vitamins, trace minerals, and other micronutrients. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 199.
Stabler SP. Megaloblastic anemias. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 150.
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