What is the optimal dose of insulin for the protein content of a meal in individuals with type 1 diabetes mellitus using intensive insulin therapy

INTERVENTION: The aim of this study is to determine a safe and effective insulin dosing schedule to account for the protein content of a meal in order to improve postprandial glycaemia without increasing the risk of hypoglycaemia (low blood glucose levels [BGL's]) in individuals with T1DM. A continuous glucose monitor (CGM) will be inserted on the day prior to the study to provide continuous measurement of BGL's. For 5 consecutive days participants will be provided with an evening meal containing identical amounts of carbohydrate, protein and fat. The meal will be a lean chicken burger. Insulin doses will be calculated using the participants usual insulin to carbohydrate ratio (ICR) with additional amounts of insulin added in increasing increments of 7.5% These additional doses will be administered over 5 days in randomised order. The additional insulin amounts will be: a) 7.5% b) 15% c) 22.5% d) 30% The insulin bolus will be programmed into the participants own insulin pump to commence delivery 15 minutes prior to consumption of the test meal, as per usual management. The insulin will be delivered using a dual wave or combination type bolus feature of the pump. The insulin will be delivered over 4 hours and the dose will be split 70/30% (70% given up front with the remaining 30% of the dose given over 4 hours). The participant will be given clear instructions of how to do this (most people using insulin pump therapy would be familiar with using wave bolus options) and the amount of insulin will be calculated by a member of the research team. Participants will be contacted daily by a member of the research team to ensure adherence to the protocol. The particpants insulin pump can be uploaded to a secure database each day for research staff to check the insulin doses and delivery. CONDITION: Type 1 Diabetes Mellitus PRIMARY OUTCOME: The primary outcome variable of this study is postprandial normoglycaemia (defined as the percent of time BGL’s remain within the target of 4‐10 mmol/l in the 6 hour postprandial period) following the different doses of additional insulin for the protein content of the test meal. This will be assessed by 24 hour continuous glucose monitoring (CGM) for the duration of the study. ; ; SECONDARY OUTCOME: Glucose excursions at 30 minute intervals for the 6 hour postprandial period by CGM Number of hypoglycaemic events in the 6 hour postprandial period (defined as BGL’s <3.5 mmol/l) assessed by CGM ; ; ; ; Peak glucose level during the 6 hour postprandial period as shown on CGM Postprandial hyperglycaemia (defined as BGL’s >10.1 mmol/l) in the 6 hour postprandial period measured by CGM Time to peak glucose level in the 6 hour glucose period measured using CGM INCLUSION CRITERIA: Ages 7‐40 years Type 1 Diabetes for <1 year, HbA1c<8% (64 mmol/mol) BMI <91st centile No other major medical conditions or complications Using insulin pump therapy