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Alternative names Return to top
Vitamin B12 absorption testDefinition Return to top
The Schilling test is used to determine whether Vitamin B12 is absorbed normally by the body.How the test is performed Return to top
The patient is given two doses of Vitamin B12 (cobalamin). The first dose is radioactive and taken by mouth. The second dose is not radioactive and is given as a shot 2-6 hours later. The injection of Vitamin B12 may sting. Urine is then collected over the next 24 hours to measure whether Vitamin B12 is normally absorbed.
This test may be performed in four different stages to find the cause of low Vitamin B12 levels. Stage I is as described above. If Stage I is abnormal, Stage II may be done 3 to 7 days later. In Stage II, patients receive radioactive B12 along with intrinsic factor.
Intrinsic factor is produced in the stomach and binds to Vitamin B12. Stage II 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. Here, the Stage II test is repeated after the patent has taken antibiotics for two weeks, and can tell whether the abnormal growth of bacterial has led to low Vitamin B12 levels. A Stage IV test determines whether low Vitamin B12 levels are caused by problems with the pancreas. Here, the patient is given pancreatic enzymes for three days, followed by a radioactive dose of Vitamin B12.
A 24-hour urine sample is needed. For adults:
For infants:
How to prepare for the test Return to top
How the test will feel Return to top
The injection of Vitamin B12 may sting.Why the test is performed Return to top
The Schilling test is performed to evaluate Vitamin B12 absorption.
Intrinsic factor is produced in the stomach and is required for Vitamin B12 absorption. If intrinsic factor is not made, the body cannot absorb Vitamin B12. Low Vitamin B12 levels can occur from the lack of intrinsic factor because of pernicious anemia, gastrectomy (partial removal of stomach), inadequate absorption due to bowel disease, bacterial overgrowth in the intestine, pancreatic insufficiency or certain medications. The Schilling test is most commonly used to evaluate patients for pernicious anemia.
The test can be falsely positive. Most of the time this is due to inadequate urine collection. Other reasons include kidney disease or problems with the lining of the small intestine.
Normal Values Return to top
Excretion of 8 to 40% of the radioactive Vitamin B12 within 24-hours is normal.What abnormal results mean Return to top
Low vitamin B12 levels can cause pernicious anemia. This can be caused by problems absorbing Vitamin B12 or not eating enough foods that contain Vitamin B12. Some other causes are removal of part of the stomach or the development of an antibody against intrinsic factor. 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 patients who have problems absorbing Vitamin B12 and intrinsic factor in the small intestine.
Abnormal Stage I and II Schilling tests may indicate:
What the risks are Return to top
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Page last updated: 28 October 2004 |