The Urinary Excretion Test for Absorption of Vitamin B12

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Abstract
A systematic study involving the use of 91 young, healthy volunteers demonstrated that certain crude intrinsic factor preparations decreased the urinary excretion of orally administered radioactive vitamin B12. On the other hand, a highly purified preparation derived from the crude concentrate or a special preparation with no inhibitory substance increased the urinary output of radioactivity. Thus, the observed decrease in urinary excretion is not due to intrinsic factor per se, but to some interfering substances present in our crude concentrates. The purified preparation is still capable of binding vitamin B12 according to the microbial absorption procedure or by the dialysis method.