A Clinical Trial Using Tirzepatide to Help Adults With Type 1 Diabetes Automatically Control Their Blood Sugar

Inclusion Criteria: * Age ≥ 18 years. * Clinical diagnosis of type 1 diabetes for ≥ 1 year, per investigator judgment (confirmatory C-peptide and autoantibodies not required). * A BMI ≥ 27 kg/m2. * HbA1c \> 6.5%, and \< 12%. * Current therapy: multiple daily injections or insulin pump. * Willingness to use Tandem Control IQ insulin pump system with the use of rapid or ultra rapid-acting insulins compatible with Tandem Control-IQ pump (e.g. Fiasp is not compatible) * Active carbohydrate counting for prandial insulin dosing. * Individuals of childbearing potential must be using or agree to use an effective birth-control method. Childbearing potential refers to participants of the female sex post-menarche who have not reached menopause and who do not have a medical condition causing sterility (e.g., hysterectomy). Post-menopausal state refers to the absence of menses for 12 months without any alternative cause. Exclusion Criteria: * Use of GLP1-RAs within the last four weeks. * Use of antihyperglycemic agents other than insulin or metformin within the last 2 weeks. * Planned or ongoing pregnancy. * Breastfeeding. * Severe hypoglycemia requiring hospitalization in the past 2 months. Severe hypoglycemia is defined as requiring the assistance of another person, due to altered consciousness, to administer carbohydrates, glucagon, or other resuscitative actions. * Diabetic ketoacidosis within the last 2 months. * History of acute or chronic pancreatitis. * Personal or family history of medullary thyroid cancer or multiple endocrine neoplasia type 2. * Severe renal impairment with eGFR \<30 mL/min/1.73 m2 (CKD-EPI), measured within the last four months. * Clinically significant proliferative diabetic retinopathy or gastroparesis, as per the judgment of the investigator. * Current or ≤ 1 month use of supraphysiological doses of oral or intravenous glucocorticoids. * History of bariatric surgery within the last 6 months. * Medical or psychiatric illness likely to interfere with participation (e.g. cirrhosis, active cancer, decompensated schizophrenia), per investigator judgment. * Inability or unwillingness to comply with safe diabetes management practices, in the view of the investigator. * Any safety concern that, in the investigator's judgment, precludes participation.