Physical activity is recognised to be an efficient measure in improving glycemic control in the treatment of type 2 diabetes. This evidence is lacking in type I diabetes but type 1I diabetics benefit from the same advantages like the general population. For many type I diabetics, especially younger patients, sport represents an important modality in the treatment of their disease but also of their quality of life. However, this is often a challenge for the patient as well as for the physician regarding the metabolic consequences (hypo- but also hyperglycemia) which can appear in relation with physical activity. There are existing general recommendations concerning the intake of carbohydrates and the reduction of insulin doses but those have to be adapted individually for each patient and depend significantly on different sports and on the intensity of sport.