Hypoglycaemia (Low Blood Sugar) in Adults With Diabetes and Adrenal Failure

The purpose of this study is to measure how often low blood sugars occur in people who live with both adrenal insufficiency (AI) and diabetes and need to take insulin. People who live with AI need to take steroid replacement tablets every day, for life. Two of the most common types of steroid replacement tablets are called prednisolone and hydrocortisone. Low blood sugar (hypoglycemia) is a very common side effect of taking insulin and can often be unpleasant, frightening and dangerous. People who have adrenal failure are also at risk of hypoglycaemia, although this is rare. It is not known whether taking steroids affects how often hypoglycaemia happens. The study has three aims: 1. To measure how often low blood sugars occur at night in people who live with with both adrenal insufficiency (AI) and insulin-treated diabetes 2. To compare how often low blood sugars occur in people taking prednisolone for their AI versus those taking hydrocortisone. 3. To compare the patterns throughout the day for low blood sugars in those taking prednisolone versus those taking hydrocortisone. The study will compare this information with results in people who have AI without diabetes. Participants will be given continuous glucose monitoring systems (Dexcom G6 devices) which are small wearable devices that measure glucose levels throughout the day and night. They will be asked to wear a device for 30 days. Participants will not be asked to make any changes to their usual medications or their diet.