Further studies on the use of serum gastrin levels in assessing the significance of low serum B 12 levels

The reported incidence of low serum vitamin B 12 levels in patients ranges from 4% to 8%. In only a small percentage can this be ascribed to readily diagnosed pernicious anemia, malabsorption syndrome, or to gastrointestinal surgery. This leaves a number of patients in whom the meaning of the low serum B 12 is not immediately apparent. In 71 patients with intact gastrointestinal tracts, hematological indices did not adequately separate patients with decreased absorption of unbound B 12 from those with normal absorption. A low absorption of B 12 , either unbound or food‐bound, was found, however, when the level of serum gastrin was elevated. In contrast, a normal absorption of unbound B 12 was likely (95% of 44 patients) when the serum gastrin was normal.