Stroke is one of the most important causes of permanent disability and death in adults worldwide. In addition to hypertension, smoking, lack of physical activity and cardiac diseases, diabetes mellitus is an independent and modifiable risk factor for ischemic stroke. To date no unambiguous evidence exists for a reduction of the incidence of stroke by normalizing and lowering of long-term glucose levels with or without drugs. Nevertheless, normalization of blood glucose is an important goal in daily clinical practice. This also applies to the acute phase after stroke. Excessive lowering of short-term and long-term glucose levels is not recommended due to the increased risk of adverse events (hypoglycemia) which outweighs possible benefits. The focus in the prevention of stroke in patients with diabetes consists of guideline-conform treatment of modifiable vascular risk factors, such as hypertension, hyperlipoproteinemia, obesity and smoking.