Diabetes mellitus and its complications constitute a major health problem in modem societies. The prevalence of the disease has increased dramatically every year. Successful treatment of diabetes involves changing life style such as exercise and physical activity, reducing body weight with diet and behavioral modifications, and using pharmacological agents. Currently, there are at least six distinct classes of antidiabetic agents available. Each class displays unique pharmacologic properties. Insulin and insulin analogues are used for treatment of both type 1 and type 2 diabetes mellitus. Sulfonylureas stimulate the production and release of insulin. The meglitinide is nonsulfonylurea agent that also works as insulin secretagogue. Unlike sulfonylureas, meglitinide requires the presence of glucose to close ATP-sensitive K+ channels and subsequently induces calcium influx. Adverse effects including hypoglycemia and cardiovascular complications are probably less pronounced than that caused by the sulfonylureas. Metformin reduce hepatic glucose and increase peripheral glucose utilization. Alpha glucosidase inhibitor, acarbose, delays carbohydrate absorption and reduces postprandial hyperglycemia by inhibition of brush border enzyme in proximal small intestine. Thiazolidinedione activates peroxisome proliferator-activated receptor gamma, leading to improve insulin sensitivity predominantly at skeletal muscles and adipose tissue, decrease serum LDL cholesterol, and increase serum HDL cholesterol. In recent clinical trials, the new drugs of diabetes therapy such as pramlintide, glucagon like pegtide-1 have been shown to slow down gastric emptying time, suppress glucagon secretion and food intake.