Schilling Test

Written by Corinna Underwood | Published on May 25, 2012
Medically Reviewed by George Krucik, MD

What is a Schilling Test?

The Schilling test is a medical procedure used to determine whether or not you are absorbing vitamin B12 properly. A doctor may choose to order this test if you are suffering from vitamin B12 deficiency, also known as pernicious anemia. This particular test, which can require up to four stages of administration, involves analysis of urine samples to help determine the source of the deficiency.

Your body uses vitamin B12 to make red blood cells. Anemia is a condition in which the body does not have sufficient healthy red blood cells to transport oxygen to organs and tissues. The test is designed to measure how well your body absorbs vitamin B12 from your digestive tract.

Purpose of Schilling Test

Your doctor may recommend the Schilling test if you have a vitamin B12 deficiency in order to determine if your stomach is producing “intrinsic factor.” Intrinsic factorequired for vitamin B12 absorption. Without it, your body will be unable to absorb vitamin B12, resulting in pernicious anemia.

Where and How the Test Is Administered

The Schilling test has four stages. After you have taken enough supplements to restore a healthy level of vitamin B12 in your system, your doctor may request that the testing be carried out over a period of several weeks.

Stage One

You will be given two doses of a vitamin B12 supplement. The first dose will be in liquid form, which will contain a “radiolabelled” dye that can be detected in the urine. Radiolabelling is when doctors or lab technicians use a radioactive (but not dangerous) element to track a compound (in this case B12) through the body. It can track where it goes, how fast it gets absorbed, and more.

The second will be given as an injection one hour later. These supplements alone are not enough to return your body’s vitamin B12 to a healthy level, but are used to test your body’s ability to absorb the vitamin.

Over the next 24 hours, you will need to collect a urine sample and deliver it to your doctor’s office so the rate of vitamin B12 absorption can be tested. If stage one is abnormal, your doctor will perform stage two within three to seven days.

Stage Two

In this stage, you will be given another oral sample of radiolabelled vitamin B12 along with intrinsic factor. This test will show whether your low levels of vitamin B12 are caused by a problem that is preventing your stomach from making intrinsic factor. You will collect a urine sample over the next 24 hours and deliver it to your doctor to be analyzed. If the results of this test are normal, it means that intrinsic factor is lacking and you have pernicious anemia. If the results are abnormal, your doctor will perform stage three.

Collecting the 24-Hour Urine Sample

Below are two sets of instructions for collecting a 24-hour urine sample—one for adults and one for infants.

For adults:

  • Day 1: Urinate into the toilet after waking up, and continue to collect all of your urine in a clean container throughout the next 24 hours.
  • Day 2: Urinate into the same container after getting up. Seal the container and label it with your name and the date. Keep it refrigerated until you can return to the doctor.

For infants:

  • Wash the area around the penis or vagina.
  • Place the urine collection bag on your child and secure the adhesive tape.
  • Place a diaper on the infant, covering the collection bag.
  • Check the infant regularly and change the bag each time it has urine in it.
  • Drain the urine into a clean container and deliver it to the doctor as soon as you have collected the required amount of urine.

Stage Three

This test is undertaken to see if your low vitamin B12 levels are caused by an abnormal growth of bacteria. Before administering this test, your doctor will prescribe you a two-week course of antibiotics. If this test is abnormal, stage four will be administered.

Stage Four

This test will show your doctor if your low levels of vitamin B12 are caused by any problems with your pancreas. In this stage, you will be given a three-day course of pancreatic enzymes followed by a radiolabelled dose of vitamin B12. You will collect a urine sample over the following 24 hours.

Understanding the Results

Normal Results

A normal result would require urinating eight to 40 percent of the radiolabelled vitamin B12 within 24 hours.

Abnormal Results

Abnormal stage one and normal stage two indicates the stomach is unable to make intrinsic factor.

Abnormal stage one and two may indicate:

  • pernicious anemia
  • celiac disease
  • liver disease
  • biliary disease
  • hypothyroidism

Abnormal stage three indicates that low levels of vitamin B12 are caused by abnormal bacterial growth.

Abnormal stage four indicates that low levels of vitamin B12 are caused by problems with the pancreas.

What Are the Risks of the Test?

Sometimes the test may produce the following minor side effects:

  • soreness or a mild reaction at the site of the vitamin injection
  • mild nausea
  • feeling lightheaded

The Schilling test may sometimes give a false positive result. Usually this is caused by poor urine collection, but it can also be due to problems with the lining of the small intestine or kidney disease. If your doctor suspects a false positive result, he or she will likely order a retest.

Preparation for the Schilling Test

Though you may drink water, you will need to avoid food for eight hours before the test. You can then eat normally after the test. You cannot have an intramuscular injection of vitamin B12 within three days before the test.

What to Expect After the Test

If you are suffering from vitamin B12 deficiency, your doctor may perform further tests to determine if it is related to any of the following factors:

  • reduced stomach acid production
  • celiac disease
  • bacterial overgrowth
  • pancreatic insufficiency
  • alcoholism
  • prescribed medications
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