Glucagon-like peptide-1 (GLP1) and their receptor agonists - beside their blood glucose lowering and central effects- affect also the gastrointestinal function in many respects. They slow down the stomach emptying, the motility of the small bowel and colon - this is the explanation for the "ileal brake" terminology -, stimulate the function of exocrine pancreatic acinar cells and increase amylase production. GLP1 receptor agonists belong to the defining tools of the blood glucose lowering therapy in type 2 diabetes. Their long- and short-acting derivatives have different influence on the fasting and the postprandial blood glucose, respectively. By introducing the term non-prandial and prandial type analogues - which seems to be forced in light of the newer data - the potential slowdown in gastric emptying is the center of interest, lately, however, especially in the case of long-acting GLP1 variants, at least such attention should be paid to controlling bowel function. The article reviews the physiological effects of GLP1 on the gastrointestinal tract and draws attention to the potential for the prevention of possible side effects through detailed patient information and dietary advises. Orv Hetil. 2019; 160(49): 1927-1934.