The goal of this observational study is to investigate if diathermy (a surgical tool that uses electrical energy to control bleeding) has any affect on the accuracy and functioning of continuous glucose monitoring systems in adults and young people with Type 1 Diabetes. The main questions this study aims to answer is -
\- Does the accuracy of continuous glucose monitoring systems change after use of diathermy?
Participants will:
* Have their height and weight checked.
* Provide information about their medical history including type of diabetes, other medical conditions and any current medications they take.
* Have paired glucose meter and sensor glucose measurements taken every 15-75 minutes from up to 4 hours before surgery until up to 4 hours after the end of surgery.
* Have two blood samples taken to measure glucose levels, The first one will be before the use of diathermy and the second will be after the use of diathermy.