Tirzepatide for the Treatment of Concurrent Type 1 Diabetes and Overweight or Obesity

Inclusion Criteria: * Age 18-70 years at screening * A clinical diagnosis of T1D for at least 12 months at time of screening * Body mass index ≥ 27kg/m2 * HbA1c ≤ 10% * Capable and willing to self-inject tirzepatide once per week * In women of childbearing potential, a negative pregnancy test and willing to use effective contraception consistently for the duration of the study * Able and willing to provide written informed consent for study participation * Able and willing to use Easy Diet Diary * Able and willing to keep an exercise log * Willing to share devices data uploads * Has current glucagon product to treat severe hypoglycaemia * Has current ketone meters to check ketones Exclusion Criteria: * Age \<18 years and \>70 years * A clinical diagnosis of diabetes type other than T1D * HbA1c \> 10% * Use of GLP-1 receptor agonist within 1 month of study screening * Use of any glucose lowering medications aside from insulin within 1 month of study screening * History of hypersensitivity to investigational medicinal product or related product * Obesity that is induced by other endocrine disorders * Pregnancy or positive pregnancy test at time of screening, or unwilling to use effective contraception consistently for the duration of the study which is defined in Appendix 1 * Active proliferative diabetic retinopathy, maculopathy, or severe no proliferative diabetic retinopathy requiring acute treatment * Known gastric emptying abnormality * History of chronic or acute pancreatitis, uncontrolled hypertension, acute cardiovascular condition within 3 months * No longer than 12 months of insulin treatment * Not willing to use a NovoPen 6 to record insulin dosing if currently using multiple daily injections * Insulin pump, CGM or smart phone devices are not compatible for data transfer * Not willing to share device data * Current use of any steroidal medication, or planned long-term steroidal treatment (\>4 weeks) during the study period * Serum triglycerides \>500 mg/dL * History of or plans for bariatric surgery during the study period * eGFR \<45 ml/min/1.73 m2 * History of severe hypoglycaemia (within 3 months of trial period) * History of diabetic ketoacidosis (within 3 months of trial period) * History of stroke (within 3 months of trial period) * History of heart failure * Planned coronary, carotid, or peripheral artery revascularisation * History of acute or chronic liver disease * History of allergy to any form of insulin, GLP-1RA or its excipients * History of malignancy requiring chemotherapy, surgery, or radiation (within 5 years of trial period) * History of multiple endocrine neoplasia type 2, familial thyroid cancer, or non-familial medullary thyroid cancer * Presence or history of malignant neoplasms or in situ carcinomas (other than basal or squamous cell skin cancer, low-risk prostate cancer, or in situ carcinomas of the cervix or carcinoma in situ/high grade prostatic intraepithelial neoplasia) within 5 years before screening * Have a pacemaker, or metal implants * Participation in other intervention trials during the study period * Existence of any additional health conditions or medical issues, including significant psychiatric disorders, that render a person unfit for the study at the discretion of the investigators