The study investigates the effects of the antidiabetic drug "Dapagliflozin" on fluctuations in blood glucose after exercise in people with type 1 diabetes. Dapagliflozin is approved for the treatment of type 2 diabetes. The maintenance of blood sugar depends on the amount of insulin, the main regulator that lowers blood sugar, and other hormones affecting the metabolism of blood glucose in the human body. The amount of hormones and insulin requirements can change rapidly during and after exercise. In addition, Dapagliflozin increases urinary excretion of blood glucose and may furthermore affect hormones that stabilize blood glucose during exercise. Study participants receive Dapagliflozin and a placebo in random order. During a defined exercise session on a stationary bicycle, changes in blood glucose and hormones affecting blood sugar maintenance are determined and compared between both conditions.