Vitamin B12 is found in animal products such as meat, shellfish, milk, cheese, and eggs. Most people who eat animal products are not likely to develop vitamin B12 deficiency anemia unless their bodies can't absorb it from food. Strict vegetarians (vegans) who do not eat animal products and babies of mothers who are strict vegetarians are at increased risk for developing anemia and should take a supplement containing vitamin B12. Vitamin B12 is stored in the liver for a year or more, which reduces a person's risk of anemia.
Vitamin B12 is usually measured at the same time as a folic acid test, because a lack of either one can lead to a form of anemia called megaloblastic anemia. Lack of vitamin B12 also affects the nervous system.
A vitamin B12 test is used to:
Do not eat or drink (other than water) for 10 to 12 hours before the test.
Your health professional drawing blood will:
The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.
There is very little chance of a problem from having a blood sample taken from a vein.
A vitamin B12 test measures the amount of vitamin B12 in the blood.
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what’s normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
More than 200–835 picograms per milliliter (pg/mL)
148–616 picomoles per liter (pmol/L) (SI units)
Reasons you may not be able to have the test or why the results may not be helpful include:
Other Works Consulted
- Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
- Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby.
|Primary Medical Reviewer||E. Gregory Thompson, MD - Internal Medicine|
|Specialist Medical Reviewer||Brian Leber, MDCM, FRCPC - Hematology|
|Last Revised||December 14, 2010|
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