After obtaining informed consent, patients with diabetes mellitus willing to participate will be invited to an initial comprehensive assessment (baseline) performed at the three cantonal study centers (Inselspital Bern, Kantonsspital St. Gallen, Universitätsspital Zürich). This will be followed by face-to-face clinical/laboratory visits between one to four times yearly according to patient's individual management plans. Once a year a comprehensive review including clinical and laboratory screening for diabetes-specific complications is planned.