Due to reports of a severely reduced insulinotropic effect of the incretin hormone glucose-dependent insulinotropic polypeptide (GIP) in type 2 diabetes (T2D), GIP has not been considered therapeutically viable in T2D. Recently, however, tirzepatide, a novel dual incretin receptor agonist (activating both the GIP receptor and the glucagon-like peptide 1 (GLP-1) receptor) demonstrated massive improvements in glycaemic control and robust body weight losses; greater than observed with the GLP-1 receptor agonist semaglutide. However, the contribution of GIP receptor activation to these effects remains unknown. The present study will evaluate the glucose-lowering effect of GIP in the context of pharmacological GLP-1 receptor activation in patients with T2D.