Schilling Test

A Schilling 24-hour urine test is done to evaluate whether vitamin B12 is being absorbed by the body. It is usually done when the results of a vitamin B12 blood test are low. The body needs this B vitamin to make blood cells and to maintain a healthy nervous system.

A lack of vitamin B12 can be caused by a lack of the vitamin in the diet or, more commonly, by a problem with absorbing the vitamin from the intestines. A substance made in the stomach called intrinsic factor helps the intestines absorb vitamin B12. If the intrinsic factor is not present, vitamin B12 may not be absorbed properly.

A Schilling test may be given in two parts. Part one measures the amount of vitamin B12 passed in urine after a known amount of the vitamin tagged with a radioactive substance is swallowed. If the intestines absorb vitamin B12 normally, a certain amount of the vitamin (up to 25% of the amount swallowed) will be passed in the urine. If the intestines cannot absorb the vitamin normally, very little or no vitamin B12 will be present in the urine.

A Schilling test with abnormal results (no vitamin B12 in the urine) may be repeated after giving an oral dose of intrinsic factor and radioactive B12. This is called part two of the test, and it tells whether the vitamin deficiency is caused by a lack of intrinsic factor or from a problem with the intestines.

The Schilling test is done to:

• Determine the cause of a low level of vitamin B12.
• Check for vitamin B12 deficiency anemia in people at high risk for developing this anemia, such as those who have had stomach or intestinal surgery, small intestine problems, or people with a family history of this anemia.
• Help diagnose pernicious anemia, a serious blood disease caused by a lack of intrinsic factor.

Do not eat or drink (except water) for 10 to 12 hours before this test. Do not take any supplements containing vitamin B12 for at least three days before having the Schilling test. Also, do not use laxatives for 24 hours before the test.

Talk to your health professional about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

• You will be given a capsule to swallow. This capsule has a very small amount of radioactive-tagged vitamin B12.
• Two hours later, you will receive a shot of nonradioactive vitamin B12 in a muscle. This nonradioactive vitamin B12 prevents the radioactive B12 from binding to tissues in the body after it is absorbed.
• You will then be asked to collect a 24-hour urine sample.
• If the level of radioactive vitamin B12 is low, a second test may be done within 3 to 7 days. During the second test, you will be given a pill of intrinsic factor with the radioactive vitamin B12. You will then need to collect another 24-hour urine sample.
• On rare occasions radioactive vitamin B12 will not be present in the urine, even after intrinsic factor is given along with the radioactive vitamin B12. This may be caused by bacteria in the intestine or a problem in the pancreas. If your health professional suspects bacteria are causing abnormal test results, a third test may be done after you take some antibiotics to destroy the bacteria. If your health professional suspects a problem with your pancreas, the Schilling test may be repeated after you take some pancreatic medicines (pancreatic enzymes).

Urine collection over 24 hours

• You start collecting your urine in the morning. When you first get up, empty your bladder but do not save this urine. Write down the time that you urinated to mark the beginning of your 24-hour collection period.
• For the next 24 hours, collect all your urine. Your doctor or lab will usually provide you with a large container that holds about 1 gal (4 L). The container has a small amount of preservative in it. Urinate into a small, clean container and then pour the urine into the large container. Do not touch the inside of the container with your fingers.
• Keep the large container in the refrigerator for the 24 hours.
• Empty your bladder for the final time at or just before the end of the 24-hour period. Add this urine to the large container and record the time.
• Do not get toilet paper, pubic hair, stool (feces), menstrual blood, or other foreign matter in the urine sample.

Swallowing the radioactive vitamin B12, the intrinsic factor pill, or collecting a 24-hour urine sample does not cause discomfort and is not dangerous.

The amount of radiation exposure from a Schilling test is too low to be harmful, except for the baby (fetus) of a pregnant woman. The Schilling test is not done on women who are pregnant or who are breast-feeding.

There are no risks with collecting a 24-hour urine sample. The amount of radioactivity in the urine isn't harmful to you or others.

In rare cases, an allergic reaction may occur to the radioactive B12 used in this test.

A Schilling 24-hour urine test is done to evaluate whether vitamin B12 is being absorbed by the body. Normal values may vary from lab to lab.

Result values

• First test is abnormal. This means that less than 8% to 10% of the radioactive vitamin B12 was found in the urine. A second test with the addition of intrinsic factor is needed to find the cause of the problem.
• Second test is normal. Adding intrinsic factor resulted in normal levels of radioactive vitamin B12. This result indicates you have pernicious anemia and are not producing the intrinsic factor you need to absorb vitamin B from your intestines.
• If the second test is also abnormal, this means that adding intrinsic factor did not result in normal levels of radioactive vitamin B12 in the urine. This result indicates another condition is the problem, such as an intestinal disease (such as sprue or celiac disease), liver disease, or an underactive thyroid gland (hypothyroidism).
• A third test may be done to determine whether the abnormal results are caused by bacteria in the intestine or a problem in the pancreas. You may receive antibiotics to kill the bacteria or pancreatic enzymes if your health professional suspects your pancreas is the problem.

Reasons you may not be able to have the test or why the results may not be helpful include:

• Not collecting exactly 24 hours of urine.
• Having kidney problems. You may be asked to collect urine for a longer period of time, such as 48 to 72 hours.
• Having a radioactive scan or radiation therapy in the past 10 days of the Schilling test.
• Taking medicines, such as colchicine, neomycin (Mycitracin), and phenytoin (Dilantin).
• Collecting stool (feces) with the urine sample.
• Using laxatives before the test.
• Having a problem with the absorption of vitamin B12. This may occur because the vitamin B12 used in the test is different than vitamin B12 found in foods. Older adults, people with gastritis, or people who do not have normal levels of hydrochloric acid in their stomach fluids may not absorb vitamin B12 normally.

• A person whose body does not have enough vitamin B12 but who has normal results from a Schilling test may have a diet lacking this B vitamin. A vitamin B12 blood test is done to evaluate the level of vitamin B12 level in the body. For more information, see the medical test Vitamin B12.
• Pernicious anemia is an autoimmune disease that is caused by a lack of intrinsic factor because the body has made antibodies to it. Intrinsic factor is a substance needed to absorb vitamin B12 from the intestines. Therapy for pernicious anemia involves regular shots of vitamin B12. People with pernicious anemia have an increased risk for developing stomach cancer and should be closely monitored by their health professionals.
• The Schilling test may not be used very much. A test for methylmalonic acid (MMA) and homocysteine may be used by most health professionals.

Other Works Consulted

• Chernecky CC, Berger BJ, eds. (2004). Laboratory Tests and Diagnostic Procedures, 4th ed. Philadelphia: Saunders.

• Fischbach FT, Dunning MB III, eds. (2004). Manual of Laboratory and Diagnostic Tests, 7th ed. Philadelphia: Lippincott Williams and Wilkins.

• Pagana KD, Pagana TJ (2006). Mosby’s Manual of Diagnostic and Laboratory Tests, 3rd ed. St. Louis: Mosby.