Currently, patients diagnosed with type 1 diabetes rely on either finger stick or sensor glucose readings when making their insulin dosage decisions. Designing a computerized system that mimics the way insulin is produced naturally in a person who does not have type 1 diabetes holds many challenges; all of which cannot be addressed in just one study. The purpose of the Medtronic Overnight Closed Loop study is to assess the performance of a system designed to automatically infuse the correct insulin dose during the hours that the patient is sleeping.

The system consists of an insulin pump that provides insulin to the patient through an infusion set. A sensor inserted just under the patient's skin measures glucose levels and a transmitter sends this information to the pump. To enable the sensor to register the glucose information correctly, it must be set (calibrated) by a finger stick blood glucose 3-4 times a day. In the commercially released system, the physician would recommend the continuous background (basal) insulin rates and the patient would be required to make decisions regarding extra insulin (bolus) for meals or as a response to high glucose levels.

In the Closed Loop System, a mobile control system is added to these devices. This consists of an Android phone, a closed loop algorithm and a translator. This system is designed to translate the sensor information and direct the pump to provide the required dosage of insulin automatically without requiring input from the patient.

Reliable calibration has proved challenging, and so it is important that the system function safely, even when calibration is inaccurate. In this study, a calibration error will be introduced under very controlled circumstances. This testing will identify if the system can maintain acceptable overnight glucose levels, regardless of whether or not calibration is ideal.

Inclusion Criteria:

• A clinical diagnosis of Type 1 diabetes as determined by the Investigator for a minimum of 36 months prior to enrollment
• Weight is between 50 and 120 kg
• Subject has used a Medtronic insulin pump for at least the previous 6 months
• Subject has an glycated hemoglobin (A1C) value ≤ 9.0% demonstrated at the time of enrollment
• Subject uses a rapid-acting analogue insulin in his/her pump

Exclusion Criteria:

• Female subject who has a positive serum pregnancy screening test, or who plans to become pregnant during the course of the study
• Subject has a history of hypoglycemic seizure or hypoglycemic coma within the past 12 months
• Subject has an exclusionary cardiac disorder