Patients with type 2 diabetes mellitus (T2DM) are not able to suppress their glucagon secretion after a meal or after ingestion of glucose. Previous studies have shown that gastrointestinal hormones might play a role in this phenomenon. However, it has not yet been possible to determine whether this lack of glucagon suppression postprandially results in an increased endogenous glucose secretion, and thus is a factor in the patients postprandial hyperglycemia.