To investigate the improvement of the course of alloxan-induced diabetes in rats by buckwheat (BW) we prepared a diet enriched with BW and fed rats with diabetic for 5 weeks. To evaluate the effects of BW the following parameters have been appreciated: body weight gain, concentration of glycated hemoglobin (gHb), the level of malondialdehyde (MDA) in the plasma and glucose tolerance test (GTT). Both values of body weight gain and GTT were successively ameliorated together with progressive supplementation of diet with BW in diabetic rats. In contrast, concentration of gHb and MDA levels were found to be significantly increased in diabetic rats fed the diet supplemented with BW. Taking into consideration all these experimental findings, we have established that the beneficial effects of BW is not uniform and apart from some gain in body weight and improvement in GTT the BW exerts unfavorable effects on gHB and the level of MDA. Such equivocal response of our diabetic rats to diet supplemented with BW may be the result of low level of antioxidants (rutin, quercetin) and trace elements such manganese in our BW seeds, which, if present, exert beneficial effects on the course of diabetes.