What is the vitamin B12 test?

This test measures the amount of vitamin B12 in your blood. Your body needs vitamin B12 to make blood cells. Nerve cells and your brain need vitamin B12 to work normally as well. You can get vitamin B12 from food and supplements.

Why is it done?

This test is done to see if your body is absorbing enough vitamin B12. If you have anemia, it may be done to see if the anemia is caused by a lack of vitamin B12.

How do I prepare for this test?

• The vitamin B12 test is often done with a test for the level of folic acid in your blood. If your folic acid level is being tested, your healthcare provider will tell you when to stop eating and drinking before the test. Food and drink before the test may affect the results.
• You may need to avoid taking certain medicines before the test because they might affect the test result. Make sure your healthcare provider knows about any medicines, herbs, or supplements that you are taking. Ask your provider before stopping any of your regular medicines.
• Talk to your healthcare provider if you have any questions about the test.

How is the test done?

Having this test will take just a few minutes. A small amount of blood is taken from a vein in your arm with a needle. The blood is collected in tubes and sent to a lab.

Ask your healthcare provider when and how you will get the result of your test.

What does the test result mean?

Some of the reasons your vitamin B12 level may be lower than normal are:

• You do not get enough vitamin B12 from the food you eat. This is unusual unless you are a vegan and eat no animal products.
• You don’t have enough acid in your stomach. For example, you may be taking medicines that lower the amount of acid made by your stomach, such as some medicines taken for ulcers or heartburn. Stomach acid is needed to get vitamin B12 out of the food you eat.
• You have pernicious anemia, which is an immune system disorder that makes it hard for your intestines to absorb B12.
• You have had an intestinal illness or intestinal surgery, which makes it hard for your intestines to absorb vitamin B12.

A low blood level of vitamin B12 is called vitamin B12 deficiency.

Some of the reasons your vitamin B12 level may be higher than normal are:

• You have too much vitamin B12 in your diet.
• You have liver disease, such as cirrhosis or hepatitis.
• You have certain other conditions, such as some types of leukemia.

What if my test result is not normal?

Test results are only one part of a larger picture that takes into account your medical history, physical exam, and current health. Sometimes a test needs to be repeated to check the first result. Talk to your healthcare provider about the results and ask questions, such as:

• If you need more tests
• What kind of treatment you might need
• What lifestyle, diet, or other changes you might need to make