The Schilling test is used to determine whether the body absorbs vitamin B12 normally.

Vitamin B12 absorption test

This test may be performed in four different stages to find the cause of low vitamin B12 levels.

Stage I: You will get two doses of vitamin B12 (cobalamin). You will take a small, first dose (a radioactive form of B12) by mouth. You will a second, larger dose by a shot 1 hour later. You will need to collect your urine over the next 24 hours, and deliver it to a lab or your doctor's office. The urine will be checked to see if you are absorbing vitamin B12 normally. For information on collecting the urine sample, see: 24-hour urine collection

If Stage I is abnormal, Stage II may be done 3 - 7 days later.

Stage II: You are given radioactive B12 along with intrinsic factor. Intrinsic factor is a protein produced by cells in the stomach lining. The body needs it so the intestines can absorb vitamin B12 efficiently.

Stage II of the test can tell whether low vitamin B12 levels are caused by problems in the stomach that prevent it from producing intrinsic factor.

If a Stage II test is abnormal, a Stage III test is performed.

Stage III: This test is done after you have taken antibiotics for 2 weeks. It can tell whether abnormal bacterial growth has caused the low vitamin B12 levels.

Stage IV: This test determines whether low vitamin B12 levels are caused by problems with the pancreas. With this test, you will take pancreatic enzymes for three days, followed by a radioactive dose of vitamin B12.

• Do not eat for 8 hours before starting the test, then eat normally for the next 24 hours. You can drink water.
• The health care provider may ask you to stop taking drugs that can affect the test.
• You cannot have intramuscular injection B12 within 3 days before the test.

The injection of vitamin B12 may sting.

The Schilling test is performed to check vitamin B12 absorption and to evaluate patients for pernicious anemia.

Additional conditions under which the test may be performed:

• Anemia of B12 deficiency
• Blind loop syndrome
• Megaloblastic anemia

Urinating 8 - 40% of the radioactive vitamin B12 within 24 hours is normal.

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.

Low vitamin B12 levels can cause megoblastic anemia.

If there is a problem with the stomach's ability to make intrinsic factor, Stage I of the test will be abnormal and Stage II will be normal.

Both the Stage I and II Schilling tests will be abnormal in people who have problems absorbing vitamin B12 and intrinsic factor in the small intestine.

Abnormal results may be due:

• Biliary disease
• Celiac disease (sprue)
• Crohn's disease
• Liver disease
• Pancreatic disease

• Local reaction to vitamin injection
• Nausea
• Feeling lightheaded

Antony AC. Megaloblastic anemias. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 167.

Antony AC. Megaloblastic Anemias. In: Hoffman R, Benz EJ, Shattil SS, et al, eds. Hematology: Basic Principles and Practice. 5th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2008:chap 39.