This is a double-blind (neither study staff or the patient will know the identity of the treatment assigned) study of canagliflozin in patients with Type 2 Diabetes Mellitus (T2DM) who are currently taking metformin at a stable dose of >=1500 mg/day. Patients will participate in the study for up to approximately 16 weeks. During the study, patients will receive 4 treatments (A, B, C, and D); each treatment will be administered during a 3-day treatment period. Patients will receive 1 dose of study medication in the morning of Day 1 and Day 2 of each treatment period and treatment periods will be separated by approximately 2 weeks. Treatments will consist of placebo (A), canagliflozin 300 mg and placebo (B), canagliflozin 300mg (C), and canagliflozin 300mg and canagliflozin 150mg (D).