Schilling test

The Schilling test is a medical investigation used for patients with vitamin B12 (cobalamin) deficiency. The purpose of the test is to determine how well the patient is able to absorb B12 from their intestinal tract. It is named for Robert F. Schilling. The Schilling test is a medical investigation used for patients with vitamin B12 (cobalamin) deficiency. The purpose of the test is to determine how well the patient is able to absorb B12 from their intestinal tract. It is named for Robert F. Schilling. The Schilling test has multiple stages. As noted below, it can be done at any time after vitamin B12 supplementation and body store replacement, and some clinicians recommend that in severe deficiency cases, at least several weeks of vitamin repletion be done before the test (more than one B12 shot, and also oral folic acid), in order to ensure that impaired absorption of B12 (with or without intrinsic factor) is not occurring due to damage to the intestinal mucosa from the B12 and folate deficiency themselves. In the first part of the test, the patient is given radiolabeled vitamin B12 to drink or eat. The most commonly used radiolabels are 57Co and 58Co. An intramuscular injection of unlabeled vitamin B12 is given an hour later. This is not enough to replete or saturate body stores of B12. The purpose of the single injection is to temporarily saturate B12 receptors in the liver with enough normal vitamin B12 to prevent radioactive vitamin B12 binding in body tissues (especially in the liver), so that if absorbed from the G.I. tract, it will pass into the urine. The patient's urine is then collected over the next 24 hours to assess the absorption. Normally, the ingested radiolabeled vitamin B12 will be absorbed into the body. Since the body already has liver receptors for transcobalamin/vitamin B12 saturated by the injection, much of the ingested vitamin B12 will be excreted in the urine.