A Study to Assess the Safety and Tolerability of Sitagliptin/Simvastatin Fixed-dose Combination (FDC) in Participants With Type 2 Diabetes Mellitus With Inadequate Glycemic Control on Metformin Monotherapy (MK-0431D-312)

Inclusion Criteria: * Has type 2 diabetes mellitus * Male, or female who is not of reproductive potential or if of reproductive potential agrees to abstain or use (or have their partner use) two acceptable methods of birth control during the study and for 14 days after the last dose of study drug * Currently on metformin monotherapy (\>=1000 mg per day) for at least 4 weeks prior to study participation * Not on statin therapy or other lipid-lowering agent for at least 6 weeks prior to study participation Exclusion Criteria: * History of type 1 diabetes mellitus or a history of ketoacidosis * History of 2 or more episodes of hypoglycemia resulting in seizure, coma or loss of consciousness over the past 3 months * On a thiazolidinedione (TZD) within the past 12 weeks * Has been treated with a statin or other lipid-lowering agent within 6 weeks prior to study participation * Is on or likely to require treatment with a prohibited medication (itraconazole, ketoconazole, posaconazole, erythromycin, clarithromycin, telithromycin, HIV protease inhibitors, nefazodone, gemfibrozil, cyclosporine, danazol, amiodarone, verapamil, diltiazem, amlodipine, ranolazine, niacin) * Intends to consume \>1.2 liters of grapefruit juice per day during the study * Is on or likely to require treatment for \>=2 consecutive weeks or repeated courses of corticosteroids (inhaled, nasal and topical corticosteroids are permitted) * Is on a weight loss program and not in the maintenance phase or has started a weight loss medication or has undergone bariatric surgery within 12 months prior to study participation * Has undergone a surgical procedure within 4 weeks of study participation or has planned major surgery during the study * History of myopathy or rhabdomyolysis with any statin * History of myocardial infarction, unstable or stable angina, angioplasty, bypass surgery, myocardial ischemia, peripheral artery disease, abdominal aortic aneurysm, transient ischemic attacks, stroke of carotid origin or \>50% obstruction of a carotid artery * Diagnosis of congestive heart failure with New York Heart Association (NYHA) Class III or IV cardiac status * History of active liver disease (other than non-alcoholic steatosis) including chronic active hepatitis B or C, primary biliary cirrhosis, or symptomatic gallbladder disease * Chronic progressive neuromuscular disorder * Human immunodeficiency virus (HIV) * Hematological disorder (such as aplastic anemia, myeloproliferative or myelodysplastic syndromes, thrombocytopenia) * Currently being treated for hyperthyroidism or is on thyroid hormone replacement therapy and has not been on a stable dose for at least 6 weeks * History of malignancy \<=5 years prior to study participation, except for basal cell or squamous cell skin cancer or in situ cervical cancer * Positive urine pregnancy test * Pregnant or breastfeeding, or is expecting to conceive or donate eggs during the study, including 14 days following the last dose of study drug * User of recreational or illicit drugs or has had a recent history of drug abuse * Routinely consumes \>2 alcoholic drinks per day or \>14 alcoholic drinks per week, or engages in binge drinking