Vitamin B12 Test
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.
- High levels of vitamin B12 can occur in liver
disease (such as
hepatitis) and some types of
leukemia. But the vitamin B12 test is not usually used
to diagnose these problems.
- In rare cases, high levels may be found
in people with
diabetes or who are
- Low levels of vitamin B12 may mean you have vitamin B12 deficiency anemia, which might be caused by problems
with the absorption of the vitamin (such as pernicious anemia).
- Low levels
may also occur following removal of part or all of the stomach (gastrectomy),
gastric bypass surgery, or gastric stapling surgery, or following surgery to
remove part of the small intestine where this vitamin is absorbed (terminal
- Low levels may mean an infection with a
parasite called fish tapeworm is
- In rare cases, low levels may mean a person is not getting
enough vitamin B12 in his or her food.
- Low levels are linked with
folic acid deficiency anemia.
- High levels of protein in
the blood, such as from
multiple myeloma, can falsely decrease blood vitamin
What Affects the Test
Reasons you may not be able to
have the test or why the results may not be helpful include:
- Taking certain medicines that might affect your test results. Tell your doctor all of the medicines that you take.
pregnant or breast-feeding.
- Taking large doses of vitamin
- Drinking large amounts of alcohol.
- Having a test,
such as a
computed tomography (CT) scan, that used dyes in the
past 7 days.
- Having pernicious anemia, which means you lack the
substance (intrinsic factor) needed to absorb vitamin B12.
What To Think About
- Folic acid levels can be high in people
who lack vitamin B12. A folic acid test is often done at the same time as a
vitamin B12 test. To learn more, see the topic
Folic Acid Test.
acid is a substance in the blood that increases when vitamin B12 levels
decrease. A methylmalonic acid (MMA) blood test may be done to help evaluate
vitamin B12 test results.
- A change in homocysteine levels may also
affect a change in vitamin B12 levels because of
metabolism changes. To learn more, see the