Schilling Test

Vitamin B12 Absorption Test

Test Overview

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.

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.

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Author:	Jan Nissl, RN, BS	Last Updated: April 13, 2007
Medical Review:	Anne C. Poinier, MD - Internal Medicine Kathleen Romito, MD - Family Medicine Brian Leber, MDCM, FRCPC - Hematology
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