Purpose: Continuous glucose monitoring (CGM) is recommended by clinical guidelines for children and adults with type 1 diabetes mellitus (T1DM) to improve clinical outcomes. In Thailand, CGM was incorporated into the Universal Healthcare Coverage (UHC) program in mid-2023. This study aimed to evaluate preliminary clinical outcomes and device adoption at a single tertiary care center. Glycemic outcomes were assessed before and after CGM use following the UHC reimbursement program and results were compared across 4 groups: self-monitoring blood glucose, CGM, open-loop insulin pump, and hybrid closed-loop (HCL). CGM adherence and parameters were also analyzed. Methods: This retrospective-prospective study collected and analyzed demographic data, hemoglobin A1c (HbA1c) levels, and CGM parameters. Results: A total of 142 T1DM patients (median age, 17.3 years; range, 3.5–69.2 years) were included. Baseline HbA1c was 8.1%±1.5%, with no significant differences among groups (P=0.223). The HCL group showed the largest HbA1c reduction at 12 months (-0.99%, P= 0.001), particularly in patients <18 years (-1.21%, P=0.014). CGM users showed improvements in HbA1c (-0.29%) and a higher proportion achieving time in range (TIR) ≥70% at 12 months (69.2% vs. 47.1%, P=0.08), though this was not statistically significant. Preliminary CGM uptake was 12% (17 of 142). The HCL group exhibited higher TIR and better sensor adherence (P<0.05), while other groups showed no significant changes. Conclusion The HCL system significantly improved glycemic outcomes, particularly in younger patients. However, CGM adoption remains low, highlighting the need for expanded access, enhanced reimbursement policies, and improved adherence strategies.