The Impact of Continuous Glucose Monitoring With a Predictive Hypoglycaemia Alert Function on Hypoglycaemia in Physical Activity for People With Type 1 Diabetes

CLINIC VISIT 1: Screening

Following informed consent study participants will give a full medical and medication history. Venous blood tests will be taken to assess HbA1c and renal function. C-peptide will be measured in participants who have not had previous tests to confirm T1DM diagnosis.. Women of childbearing age will have a urine pregnancy test. An ECG will be performed in participants with longstanding Type 1 Diabetes Mellitus (>10 years) or participants who are >40 years old.

CLINIC VISIT 2: Run-in

If participants meet the inclusion criteria they will be enrolled on to the study, within a month of screening and at a time that is convenient to them. For the 10 days of the run-in period, participants CGM will be blinded, meaning that they will be wearing the CGM sensor but will not see any of the glucose data. They will wear a sensor which will be attached to a transmitter which will send data to a Dexcom receiver. The receiver must be kept within 6 meters of the transmitter most of the time as the transmitter can only store three hours of data. After the run in they will be able to use the Smartphone app instead of carrying the receiver if they wish. They will be taught to insert the sensor at the run-in visit, and provided with spares in case of sensor failure. Participants will be instructed to test their capillary blood glucose levels and self-manage their type 1 diabetes as normal during the run-in period. The run in phase will last 10 days.

Data on food intake, and insulin usage will be collected for the full duration of the study using a smart phone app (mySugr) in those treated with insulin injections, or using the built-in system in the pumps of those using insulin pump therapy. Both the app and the insulin pumps allow participants to input their own insulin doses, or use the bolus calculator which uses the participant's individual insulin:carbohydrate ratio to help calculate insulin doses based on the carbohydrate intake. There will be no change in participants' insulin dosing, and participants will make all their insulin dosing decisions themselves, based on their pre-study insulin:carbohydrate ratios. The advantage of using the app or bolus advisor is that the tracking of the insulin action (which lasts for 3-5 hours) allows participants to see how much insulin is still active. This is important when the CGM is unblinded as it can prevent participants giving additional insulin unnecessarily when they see their blood glucose levels on the CGM. Those using insulin injections will be provided with a smart insulin pen, a device similar to the participants' usual insulin delivery device use, but with a memory capable of storing dosing data until the end of the study (Inpen, produced by Companion Medical).