Study design and Methodology General Design: 18 male or female type 1 diabetes (T1DM) individuals aged between 18 and 50 years old will be invited to attend four laboratory sessions, each separated by 7 days. Participants will be recruited in clinic and through advertising in local media. Participants will complete four main trials in a randomised and counter balanced fashion. Main trials will involve the manipulation of both the meal composition (fat content) and rapid-acting insulin dose. During each visit blood samples will be measured over a 6 hour postprandial period to determine glycaemic, lipaemic, hormone, and metabolite parameters.