Study to Evaluate the Efficacy of Acarbose,Metformin,Sitagliptin Combination Treatment in DM Patients

Inclusion Criteria: 1. Subjects with type-II diabetes mellitus; 2. Subjects aged between 20 and 80; 3. Subjects whose HbA1c ratio is between 7.0% and 10.0%; 4. Subjects who took Metformin and Sitagliptin for at least 12 weeks; 5. Subjects who were given the explanation about this clinical study and signed the consent form. Exclusion Criteria: 1. Subjects who have taken drugs that are likely to affect blood glucose or who need to take such drugs, e.g., glucocorticoid; 2. Subjects with severe renal diseases (men: Scr\>1.5 / women: Scr\>1.4); 3. Subjects with severe liver diseases or whose AST and ALT are at least 2.5 times higher than the upper limits of normal (ULN); 4. Subjects having the case history of lactic acidosis; 5. Subjects who have the case history of myocardial infarction or unstable angina or who underwent the coronary artery bypass graft 6 months before the screening test or who have arrhythmia to be treated; 6. Subjects with congestive heart failures to be treated; 7. Subjects who fall into New York Heart Association (NYHA) class III or IV; 8. Subjects having the case history of acute or chronic metabolic acidosis including ketoacidosis; 9. Subjects who have been pregnant or who are in the period of lactation; 10. Subjects diagnosed with malignant tumors within 5 years; 11. Subjects who are hypersensitive to Metformin, Sitagliptin and Acarbose or their ingredients; 12. Subjects with inflammatory bowel diseases or intestinal ulcers or enterostenosis (includes Subjects who are vulnerable to enterostenosis) or chronic enteric diseases related to digestion and absorption or whose symptoms are likely to worsen due to intestinal gas; 13. Subjects who participated in other clinical studies as Subjects within 60 days before this study (or before taking the investigational drugs); 14. Subjects judged unfit for this study by investigators.