Incretin therapy is based on the antidiabetic actions of the incretin hormone GLP-1. The treatment both stimulates insulin secretion and inhibits glucagon secretion, which results in lowering of both fasting and postprandial glycemia. Incretin therapy is used either with GLP-1 receptor agonists or with inhibitors of DPP-4, which is the enzyme that inactivates endogenously released GLP-1. The GLP-1 receptor agonists are injected subcutaneously once or twice daily, or once weekly, and they reduce HbA1c and bodyweight. The GLP-1 receptor agonists are highly tolerable and, apart from nausea and vomiting during the early phases of the treatment, there is a low risk of adverse events. Studies on long-term cardiovascular safety are ongoing. Added advantages are very low risks of hypoglycemia and reduction in bodyweight. GLP-1 receptor agonists are efficacious in combination with oral antihyperglycemic agents and with insulin. Their main use is as an add-on to metformin in patients who are insufficiently controlled on metformin alone, and an important indication is also in combination with insulin therapy.