Low blood sugar at night (called nocturnal hypoglycemia), can often happen without symptoms and can last for a long time. Doctors often suggest that patients take a bedtime snack to try to prevent low blood sugar at night from happening, but it is not known what type of snack is best to take. We are conducting a study to evaluate how two different types of snacks affect how often the blood sugar is too low overnight. One snack will be a primarily carbohydrate snack and the other will be a carbohydrate snack with fat. The snacks will be provided by the study.

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)

The Freestyle Navigator, provides a glucose reading every 60 seconds (or 1440 readings a day). Each sensor is designed to provide readings for up to 120 hours. It has alarms for hypoglycemia and hyperglycemia and for projected high and low glucose values. The alarm set points can be adjusted by the user. The Navigator also has a trend arrow indicating the glucose rate of change (>-2 mg/dL/min, -2 to -1 mg/dL/min, -1 to 1 mg/dL/min, 1 to 2 mg/dl/min, and >2 mg/dl/min). Subjects can enter events, such as when they took insulin, ate, or exercised. The sensor requires calibration values to be entered 3 times during the first day of wear, and then 2 additional times during the 5-day wear period. The values are entered directly into the Navigator which has a Freestyle home glucose meter built into the unit. The Navigator has not yet been approved by the FDA. The Navigator currently under review by the FDA will limit sensor wear to 3 days.

This study is being done to see if there is a difference in low blood sugar overnight after having a bedtime snack made up of carbohydrate compared to a carbohydrate snack with more fat.