Modern living is associated with an epidemic of type 2 diabetes mellitus (T2DM). Sleep disturbances are strong independent risk factors for incident diabetes. Melatonin has been implicated in regulation of circadian rhythm and sleep, but it is also ascribed anti-oxidative properties and effects on glucose homeostasis. A potential association between melatonin and T2DM has only been addressed in few human physiological studies, but the topic has received renewed interest since genetic-epidemiological studies have pointed to a role for melatonin in the development of the disease. In the current study, the investigators wish to examine whether treatment with synthetic melatonin induces physiological changes that affect the risk of developing type 2 diabetes. Two studies of the physiological effects of melatonin are included in the present protocol. In study A, the investigators will examine the acute effects of Melatonin on insulin secretion and insulin sensitivity using a Botnia clamp and in study B the investigators will examine the potential effects of Melatonin on the incretin response.