Dapagliflozin lowers glucose (sugar) levels in the blood by blocking the effect of specific molecules (small particles) in your body called sodium-glucose transporters. Under normal circumstances, the sodium-glucose transporters in the kidney prevent glucose in your blood stream from leaving your body through your urine. Dapagliflozin inhibits the sodium-glucose transporters and lowers your blood glucose by allowing glucose removal through the urine. Dapagliflozin may also mildly decrease body weight and lower blood pressure in certain patients. In this study, dapagliflozin will be compared with placebo. The placebo will look like dapagliflozin but is inactive. Patients will be randomly chosen to receive either dapagliflozin or placebo and neither the physician nor the patient will know which they are receiving until the entire study is completed. Patients will continue to take to take their regular diabetes medications, unless their diabetes is very well controlled in which case their dose of insulin or oral diabetes medication may be decreased.