AIMS: To characterize trends in obesity and prescriptions for glucagon-like peptide-1 receptor agonists (GLP-1RAs) across body mass index (BMI) categories among US youth and adults with type 1 diabetes (T1D) from 2008 to 2023. MATERIALS AND METHODS: Patients with T1D were identified using a validated algorithm using de-identified electronic health record (EHRs) data from 33 US health systems. BMI categories were based on age- and sex-specific percentiles for youth (2-19 years) and World Health Organization cut points for adults (≥20 years). Trends in obesity and GLP1-RA prescriptions were characterized by BMI categories among youth and adults with T1D from 2008-2011 to 2020-2023. RESULTS: From 2008-2011 to 2020-2023, the prevalence of obesity among youth with T1D increased from 18.1% (95% confidence interval [CI], 17.3%-18.9%) to 26.0% (25.2%-26.8%) (p-for-trend <
0.001). Among adults with T1D, the prevalence of obesity rose from 30.5% (30.0%-31.0%) in 2008-2011 to 38.1% (37.8%-38.5%) in 2020-2023 (p-for-trend <
0.001). Obesity was highest in Black and Hispanic youth and adults, and racial and ethnic disparities persisted over time. Over the last 15-year period, GLP-1RA prescriptions significantly increased across all BMI categories in a dose-response manner among both youth and adults with T1D (all p-for-trend <
0.001). CONCLUSIONS: Over the last 15-year period, obesity has reached epidemic levels in US youth and adults with T1D, with significant disparities among racial and ethnic minoritized populations. These findings, coupled with the increase in GLP-1RA prescriptions, underscore the urgent need for data on GLP-1RAs' safety and effectiveness and guidance for obesity management in T1D.