Bound vitamin B 12 absorption in patients with low serum B 12 levels

In many patients with low serum levels of vitamin B 12 , the absorption of the free vitamin has been normal. The present study, using a total body counter 57 CoB 12 absorption method that clearly separated those with intrinsic factor deficiency from controls, found that of 94 patients with low B 12 levels and intact stomachs in whom the absorption of free and bound B 12 was determined, 44 (47%) had normal absorption of both. However, 20 of the 94 (21%) with normal absorption of free B 12 had low absorption of bound B 12 . The remainder (32%) had low absorption of both free and bound B 12 . All patients with high serum gastrin levels had low bound B 12 absorption, but so did 21% of those patients with normal serum gastrin levels. © 1992 Wiley‐Liss, Inc.