The study is a single-center, randomized, placebo-controlled study with a cross-over design and examines the glucagon response during a hyperinsulinemic hypoglycemic phase after a 6-week treatment with lixisenatide (or placebo) as add-on to basal insulin and metformin. The hypothesis of the study is that the glucagon counterregulation to hypoglycemia in patients treated with lixisenatide and basal insulin is not lower than in patients treated with basal insulin.