A two-part study to demonstrate the bioequivalence of a single dose of the Final Market Image (FMI) of sitagliptin /metformin (50/500 and 50/1000 mg) Fixed-Dose Combination (FDC) tablet and co-administration of a single dose of sitagliptin (50 mg) and metformin ( 500 or 1000 mg) as individual tablets. Subject will only participate in one part, receiving treatment A and B (Part I) or Treatment C and D (Part II).

Inclusion Criteria:

• Female subjects of reproductive potential test negative for pregnancy and agree to use appropriate contraception
• Subject is in good health and is a non-smoker
• Subject is willing to avoid strenuous physical activity during the study
• Subject agrees to refrain from eating grapefruit or grapefruit products during the study

Exclusion Criteria:

• Subject has a history of neoplastic disease (cancer), stroke, chronic seizures, or major neurological disorder. Subject has a history of clinically significant endocrine, gastrointestinal, cardiovascular, hematological, hepatic, immunological, renal, respiratory, or genitourinary abnormalities or diseases
• Subject consumes excessive amounts of alcohol or caffeinated beverages
• Subject has donated blood, had surgery or participated in another clinical study within the past 4 weeks
• Subject has a history of significant multiple and/or severe allergies to prescription or non-prescription drugs or food
• Subject has a history of hypersensitivity to metformin, sitagliptin, or sitagliptin/Metformin
• Subject is a regular user or past abuser of any illicit drugs
• Subject is unable to refrain from or anticipates the use of any medication, including prescription and non-prescription drugs or herbal remedies during the study.
• Subject is a nursing mother