This is a comprehensive pathophysiological study assessing various gastric functions in patients with diabetes mellitus. The investigators aim to examine the stomach with various measurement devices to gain information about its different functions and malfunctions. After the initial measurements, the examinations will be repeated after a year in each patient. Changes in the measurement values will be examined and their relations to each other and to the overall health of the patients will be investigated. For example it is hypothesised that diabetic patients also suffering from functional dyspepsia or gastroparesis will also show some changes in the function of the pyloric muscle.