The purpose of this study is to analyze the differences of blood sugar level and glycemic variability between sulfonylurea and DPP-4 inhibitor groups applying CGMS for a chosen number of type 2 DM patients. The investigators also reveal influences of each drugs on cardiovascular risk factors by measuring related biomarkers.

We enroll patients with type 2 DM with uncontrolled glucose level on Metformin monotherapy over 1000mg /day (HbA1C over 7%).

Before drug administration, we conduct basal lab study including CGMS. After 3 month of random administration of vildagliptin or glimepiride, we check CGMS, glucose levels, CV biomarkers, and estimate hypoglycemic index. We replace with the other drug for 3 months, and then conduct the same measurements. No wash-out period is necessary since result variables are measured after the 3 months of administration for a different drug.

Inclusion Criteria:

• with type 2 DM
• with uncontrolled glucose level on Metformin monotherapy over 1000mg /day (HbA1C over 7%). Provided that the tolerance for metformin is poor, enrollment of patients with lower dose of metfomrin is open.
• who have never been prescribed with test drugs, sulfonylurea or DPP-4 inhibitor/GLP-1 analogue in 3 months
• who can be applied with CGMS

Exclusion Criteria:

• who has liver function abnormality or renal function abnormality
• who has any kind of diseases, operations, medical treatments that can affect glucose levels