1) The Schilling test evaluates a patient's ability to absorb vitamin B12 by measuring the amount of radioactive B12 excreted in urine after oral administration. 2) If a patient can absorb B12 normally, the radioactive B12 will enter the bloodstream and be excreted in urine. If absorption is impaired, it will pass through the digestive tract and be excreted in feces. 3) Giving intrinsic factor along with radioactive B12 can determine if a patient's B12 absorption issue is due to intrinsic factor deficiency, as is the case with pernicious anemia.