A Double-Blind, Randomized, Active-Comparator (Metformin) Controlled, Clinical Trial to Study the Efficacy and Safety of the Strategy to Start Patients With Type 2 Diabetes Mellitus on Janumet™ Compared to Metformin

Inclusion Criteria: * All laboratory measurements are to be performed after an overnight fast ≥ 10 hours in duration. Patients with laboratory screening values/findings not meeting protocol inclusion criteria may, at the discretion of the investigator, have one repeat determination performed. If the repeat value satisfies the criterion they may continue in the screening process. Only the laboratory test not meeting inclusion should be repeated (not the entire panel). Exclusion Criteria: Glucose Metabolism and Therapy Criteria * Patient has a history of type 1 diabetes mellitus or history of ketoacidosis. Patients Requiring Specific Treatments * Patient has symptomatic hyperglycemia requiring immediate initiation of insulin therapy. * Patient has a history of intolerance or hypersensitivity to metformin or sitagliptin or has any contraindication to use metformin. Concomitant Disease of Organs and Systems * Patient has a medical history of active liver disease (excluding hepatic steatosis). * Patient has severe active peripheral vascular disease (e.g., manifested by claudication with minimal activity, a non-healing ischemic ulcer, or disease which is likely to require intervention such as with bypass or angioplasty). * Patient has unstable or acute congestive heart failure. * Patient has a history of malignancy without documentation of remission/cure. Other Criteria * Patient is pregnant, has a positive urine pregnancy test at Visit 1, is expecting to conceive within the projected duration of the study, or is breast feeding. Exclusion Criteria Based on Lab Abnormalities * Patient has increased serum-creatinine and/or decreased estimated creatinine clearance. * If screening labs are repeated, the last laboratory draw/result should be used for inclusion.§ Either elevated Creatinine or decreased estimated creatinine clearance lead to exclusion of the patient. * Patients whose serum creatinine does not meet the exclusion criteria, but whose estimated creatinine clearance is \<60 mL/min but ≥50 mL/min, may have a measured creatinine clearance (i.e., based upon a 24-hour urine collection). These patients may be eligible if their measured creatinine clearance is ≥60 mL/min. At Visit 2 * Patient has a site fingerstick glucose \<130 mg/dL (7.2 mmol/L) or \>320 mg/dL (17.8 mmol/L). Note: If the patient meets this exclusion criterion AND the investigator believes that the value does not reflect the patient's recent glycemic control based upon recent SBGM values and/or the Visit 1 FPG value, the patient should not be excluded at this time. The current visit should be changed to an "Unscheduled visit" and the patient should be rescheduled for Visit 2. If, at the rescheduled Visit 2, the patient meets this exclusion criterion, the patient MUST be excluded. * Patient has a positive urine pregnancy test. * Patient developed a new medical condition, suffered a change in status of an established medical condition, developed a laboratory abnormality, or required a new treatment or medication between Visit 1 and Visit 2 which meets any previously described study exclusion criterion.