Diabetes mellitus is characterised by insufficient insulin secretion and/or insufficient utilisation of glucose. It results in hyperglycemia which is the main reason for the development of late complications of diabetes mellitus. Postprandial hyperglycemia is important in the development of complications because it is accompanied with oxidative stress, inflammation and finally with endothelial dysfunction. Under investigation are superoxide dismutase, catalase, L-propionyl-carnitine, lipoic acid, LY 333351, PJ34, FP15 which is expected to be useful in oxidative stress and early prevention of complications. As opposed to these substances which are still under investigation, drugs like thiazolidinediones, statins and renin-angiotensin system inhibitors have proven, antioxidant effect, aside of their already known clinical indications. Today we have a lot of opportunities to reduce hyperglycemia but also oxidative stress, inflammation and disturbances of coagulation system, and so prevent in very early stages endothelial dysfunction and consequently the late complications of diabetes.