Schilling test

Alternative names

Vitamin B12 absorption test

Definition

The Schilling test is used to determine whether Vitamin B12 is absorbed normally by the body.

How the test is performed

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:

• On day 1, urinate into the toilet after getting up in the morning.
  
• Collect all subsequent urine (in a special container) for the next 24 hours.
  
• On the morning of day 2, urinate into the container after getting up.
  
• The test is now complete.
  
• Cap the container. Keep it in the refrigerator or a cool place while urine is being collected.
  
• Label the container with your name, the date, the time you last urinated, and return it as instructed.
  

For infants:

• Thoroughly wash the area around the urethra.
  
• Open a urine collection bag (a plastic bag with an adhesive paper on one end), and place it on your infant.
  
• For males, the entire penis can be placed in the bag and the adhesive attached to the skin. For females, the bag is placed over the labia.
  
• Place a diaper over the infant (bag and all). The infant should be checked frequently and the bag changed after the infant has urinated into the bag. For active infants, this procedure may take a couple of attempts - lively infants can displace the bag, causing an inability to obtain the specimen.