Abstract Disclosure: P. Panjawatanan: None. N. Radovanovic: None. R.J. Comi: None. Introduction: Insulin therapy is the mainstream treatment in patients with Type 1 diabetes. The use of insulin, though mimicking normal physiology, is associated with weight gain. Glucagon-like peptide 1 (GLP-1) agonists are a class of antidiabetic medication that lowers blood sugar levels and helps promote weight loss. We propose that GLP-1 agonists can reverse the trend of weight gain and help lower hemoglobin A1C (A1C) levels in patients with Type 1 diabetes who were gaining weight. Method: A retrospective chart review was performed at a single institution’s endocrine practice over five years. Patients with Type 1 diabetes with concomitant GLP-1 agonists used for at least one year were included. Observed outcomes were the change in A1C, weight, and basal insulin use compared at baseline, 6 months, and 12 months using mixed models repeated measures. The result was reported as estimated means (95%CI). Statistical significance was determined by a p-value less than 0.05. Results: There were 49 patients included in the study. The mean age was 44.7 years old. There were 32 females (65.3%) and 17 males (34.7%). The mean duration of diabetes was 24.6 years. Thirty-five patients (71.4%) used insulin pumps, and fourteen (28.6%) were on multiple daily injections. Overall, patients had been gaining an average of 2.0 kg per year. After the treatment with GLP-1 agonists, weight was significantly reduced at 12 months (90.0 kg (95%CI 84.9-95.1), p<0.001) compared to baseline (97.6 kg (95%CI 92.7-102.5)). The A1C was significantly improved at 12 months (7.6% (95%CI 7.2-7.9), p<0.001) compared to the baseline (8.2% (95%CI 7.9-8.6)). Total daily basal dose was significantly reduced at 12 months (35.8 units (95%CI 29.8-41.9), p<0.001) compared to the baseline (39.2 units (95%CI 33.3-45.1)). The improvement in the parameters was more pronounced at 6 months after treatment but persisted at 12 months. Conclusion: Weight gain is a consequence of insulin usage in both Type 1 and Type 2 diabetes, which considerably impacts treatment outcomes and the development of comorbidities. We conclude that GLP-1 agonists are helpful to reverse the trend of weight gain and help lower A1C levels in patients with Type 1 diabetes who require life-long insulin treatment. Presentation: 6/3/2024