The ability of the body to utilize glucose may be ascertained by measuring its glucose tolerance. The present work was devoted to study the role of different therapeutic doses of cimetidine and ranitidine on glucose utilization in normal and gastrointestinal-induced ulcer in rats. Two groups of male albino rats were used in this study , one received three oral cimetidine doses, (54 mg kg^-1, 108 mg kg^-1 and 216 mg kg^-1, respectively). The second group was given three oral ranitidine doses(13.5 mg kg^-1, 27 mg kg^-1, 54 mg kg^-1, respectively) which they comparable to a half, and double daily human therapeutic doses. Rats in each group served as their own control and doses were given in three successive trials, carried out at weekly intervals, prior to oral determinations revealed that the marked increase in glucose tolerance were glucose load of 1.0 g kg ^-1 b.wt. Serial post loading parallel to the rising therapeutic doses of cimetidine and ranitidine. Induction of gastrointestinal ulcer in a group of rats subjected to treatment with oral dose of 10 mg kg ^-l indomethacin for five successive days and then treated with both drugs for three months, revealed a common significant decrease in monthly recorded serum glucose. The magnitude of the decrease parallel to the increasing therapeutic doses of both drugs.