The effect of a single i.p dose of glucose (1.67g / kg body wt.) on the blood sugar level was examined to study the glucose tolerance test (GTT) in the Nile fish Clarias gariepinus. This study also dealt with the effect of orally administered aqueous extract of lupine or fenugreek seeds on the improvement of GTT. On the other hand, the ameliorating effects of these legumes on the histological changes as well as on the glycogen content in the kidney of the fish treated with either a single dose of alloxan (300 mg / kg body wt) or repeated injected doses of glucose (RDGI) (1.67g / kg body wt for 4 days) were tested. The GTT curve peaked at approximately 2hr and the induced hyperglycemia continued to more than 24hr suggesting that Clarias gariepinus is glucose intolerant. On the other hand, the data show that lupine seeds extract ameliorating effect on the GTT was more than that of fenugreek. In the kidney, alloxan and glucose administrations induced pathological lesions in the form of hydropic degeneration of some renal tubules cells, conspicuous areas of necrosis as well as great widening of Bowman’s space due to shrinkage of glomerular tufts. In addition, these treatments led to glycogen accumulation in the kidney. The main cause of such effects may be attributed to the prolonged hyperglycemia. All these lesions were restored after the administration of lupine or fenugreek extracts for 4 days. The ameliorating effect of such extracts may be due to their stimulatory effect on the blood glucose clearance.