As part of the study, a continuous glucose sensor (the Freestyle Navigator) will be worn overnight. The Freestyle Navigator was developed by Abbott Diabetes Care. This sensor uses a glucose oxidase based electrochemical sensor, and is designed to measure blood glucose levels in a range of 20-500 mg/dl. The sensor is inserted subcutaneously and measures interstitial glucose. In human studies the interstitial glucose levels generally lag behind the blood glucose by 3 to13 minutes.(27, 28)