Pathophysiology of T2DM is known as tissue resistance for insulin and progressive beta cell failure. Which one attributes first is unclear, but non-obese T2DM patients often show normal fasting plasma glucose (FPG) but postprandial plasma glucose (PPG) level is high and reduced or lacking normal compensatory insulin secretion. In Korea, more than 80% of T2DM are non-obese type (BMI >= 27 ) and it was observed that basal insulin level and compensatory insulin secretion reaction were reduced in normal healthy population. Based on that, metformin is an established first line treatment for type 2 diabetes, acting primarily to enhance hepatic and peripheral insulin sensitivity. However, it has become increasingly apparent that many patients require a combination of agents to attain optimal glycemic control.