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. If the intrinsic factor is not present, vitamin B₁₂ may not be absorbed properly.

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 February 8, 2007
Medical Review:	Kathleen Romito, MD - Family Medicine Brian Leber, MDCM, FRCPC - Hematology
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