The Schilling test determines the ability of a patient to absorb vitamin B12 (cobalamin) under different circumstances. This can help evaluate a patient with vitamin B12 deficiency by identifying malabsorption.


Patient preparation:

(1) overnight fast

(2) no recent vitamin B12 therapy

(3) no recent exposure to radiopharmaceutical agents

(4) The patient should not be pregnant.


Methodology - Stage 1

(1) A dose of radiolabeled vitamin B12 (using Cobalt-57) is administered orally.

(2) A large IM parenteral dose of vitamin B12 is given, sufficient to saturate hepatic uptake. This will result in any orally absorbed vitamin B12 being excreted in the urine.

(3) Urine is collected for 24 hours with the specimen kept refrigerated or on ice.

(4) The urine is then analyzed for total radioactivity.


percent absorbed and excreted =

= (total radioactivity in the urine) / (administered radioactivity) * 100%


Methodology - Stage 2:

(1) Wait at least 5 days after Stage 1.

(2) As for stage 1, except that the oral dose of radiolabeled vitamin B12 is administered with intrinsic factor.


Cautions when doing the test:

(1) Do not collect samples for other RIA analysis after administration of the radioactive vitamin B12 for several days.

(2) Incomplete urine collections can result in falsely low values of urinary vitamin B12 excretion.

(3) Fecal contamination in urine sample may cause a falsely high value of urinary vitamin B12 excretion.



• Normally > 10% of the administered dose of radioactive vitamin B12 should be excreted in the urine.

Stage 1

Stage 2




normal absorption; dietary deficiency or failure of vitamin B12 to dissociate from food



lack of intrinsic factor (pernicious anemia, gastric resection, synthesis of a defective protein)



bacterial overgrowth, pancreatic insufficiency, malabsorption due to ileal defect, fish tapeworm (Diphyllobothrium latum)



Testing Variations


vitamin B12 after therapy with a course of oral tetracycline (Stage 3)

bacterial overgrowth syndrome

vitamin B12 with administration of pancreatic extract

pancreatic insufficiency

increased time period for the urine collection

renal insufficiency (normal absorption but delayed excretion)


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