What Is a Schilling Test?

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According to the Schilling test definition written in Merriam-Webster medical dictionary the examination is an in-vivo diagnostic procedure intended to state whether the patient is able to soak vitamin B12 (cyanocobalamin). The analysis is named after R. Schilling, MD. Once it has been the golden standard for malignant anemia diagnostics but nowadays it is administrated rarely.

The GP orders this analyses if intrinsic factor shortage or pernicious anemia is suspected. Commonly the Schilling test includes 4 steps. You need to bring urine samples to determine the cause of the lack of vitamin. Cyanocobalamin is indispensable for the growth and differentiation of erythrocytes. If the RBC pool is low, tissues do not receive an adequate dose of oxygen. That is when anemia occurs. The test is conducted to assess the effectiveness of the bowel for the intake of vitamin B12.

Indications for Investigation

Your GP orders to perform the Schilling test to confirm B-12 deficiency. The medical examination shows whether your gastro produces enough intrinsic factors. To understand what is a Schilling test, you should know how B12 is absorbed. Gastromucoprotein is required to bind and transfer B12 to your bloodstream. If cyanocobalamin is absorbed incorrectly, then it will stay in your bowel and be excreted from the body in the feces. Without an intrinsic factor, it is impossible to suck in B12 and its shortage will result in pernicious anemia. Due to it the examination is also identified as pernicious anemia test.

Preparation for the Test

As the Schilling test for malignant anemia determines the natural potency of your bowel to assimilate B12, you should not receive any injections of it within 3 days before your screen. You should drink water, but not alcohol, energy shots, sweet coffee or tea. Avoid eating for at least 8-12 hours, but feel free to eat normally after the end of the analysis.

Schilling Test Procedure

So the Schilling test is rather ingenious as radiogenic B12 is required to estimate the potency of your bowel to bind and expose vitamin. When the rate of B12 has been restored to a health conscious level in your body your GP recommends you to undergo the screen. The procedure includes 4 steps and can take several weeks.

Step 1

You are given two doses of B-12 additives. The radioactive dye in liquid form helps to track where the vitamin goes how and fast your body assimilates it. Dye is a harmless element. In an hour the doctor will give a parenteral infusion of the second sample. These additives are used to to assess the ability to take a vitamin, but not to restore its deficiency.

During the next day you should gather a urine sample and bring it to your GP office to measure the rate of vitamin intake. If the results in steps 1 vary from standard, your GP will advise you to undergo stage 2 within the next 3-7 days.

Step 2

Again you will be given another oral dose of radiolabeled B12 along with intrinsic factor. This step is administrated to determine whether an intrinsic factor shortage is the underlying reason for your hypovitaminosis. Over the next 24 hours gather and bring another urine sample. The normal results confirm the lack of the intrinsic factor and pernicious anemia. The abnormal outcomes require step 3.

Step 3

This step is done to confirm the abnormal bacteria proliferation that result in vitamin B12 deficiency. For the next 14 days you should take antibiotics. Then another portion of vitamin labeled with a radioactive isotope will be given to you. Step 4 will be administrated in case of abnormal results.

Step 4

If the pancreas dysfunction is responsible for the lack of B12 this step will confirm it. Your GP will prescribe you pancreatic enzymes for 3 days. The course will be followed by the intake of B-12 radiolabeled sample. And then again gather urine over the following 24 hours.

How to Collect a 24-hour Urine Sample

For adults

On the first day urinate after you have woken up. Note down the time and collect all of your urina into a sterile container within the next 24 hours. On the second day eliminate urine into the receptacle after your sleep. Seal the tank and sing the name and the date. Keep the container in the fridge until it can be delivered to your GP.

For infants

  • Wash the area around baby’s genitalia.
  • Place the urine drainage bag on the infant and fasten the bonding adhesive.
  • Cover the bag with a diaper.
  • Change the urology bag regularly.
  • Collect the urine into a sterile tank.
  • When the required portion of urine is collected, mark the tanks with name and date and send it to the GP.


If 8-40% of the radiolabeled vitamin b-12 is found in patients 24-hour urine sample this result is considered to be within normal limits.

If step 1 of Shilling’s test shows abnormal results your – gaster cannot secrete intrinsic factor.

Abnormal results of steps 1 and 2 may indicate:

  • pernicious anemia;
  • gluten sensitive entheropathy;
  • hepatic disorder;
  • biliary dysfunction;
  • thyroid insufficiency.

Abnormal step 3 outcomes confirm the abnormal bacterial proliferation as the reason of your lack of vitamin.

Abnormal step 4 reveals that your pancreas functional impairment is causing low rates of B12.


If a vitamin B-12 deficiency is confirmed the GP should order subsequent examinations to diagnose whether or not pernicious anemia is related to the following factors:

  • gastratrophia;
  • gluten sensitive entheropathy;
  • chronic cicatrizing enteritis;
  • Graves-Basedow disease;
  • bacterial overgrowth;
  • pancreatic disfunction;
  • alcoholism;
  • prescribed drugs.

A false-positive result means that the examination indicates the condition that you don’t have at all. The Schilling’s test sometimes gives a false outcome. The most frequent reason for the mistake is a poor or improper urine collection. Along with that false results may occur due to renal diseases or impairment of the intestine lining. False-positive result require follow-up screen.


  • Brugge, William R., et al. “Development of a dual label Schilling test for pancreatic exocrine function based on the differential absorption of cobalamin bound to intrinsic factor and R protein.” Gastroenterology 78.5 (1980): 937-949.
  • Doscherholmen, Alfred, Stephen Silvis, and Jean McMahon. “Dual isotope Schilling test for measuring absorption of food-bound and free vitamin B12 simultaneously.” American journal of clinical pathology 80.4 (1983): 490-495.
  • Rath, Charles E., et al. “Effect of renal disease on the Schilling test.” New England Journal of Medicine 256.3 (1957): 111-114.

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