Association of Antidiabetic Medication Regimens and Medication Adherence With HbA1c Reduction in Type 2 Diabetic Patients: A Retrospective Study

Background Effective management of type 2 diabetes mellitus (T2DM) requires not only appropriate pharmacological therapy but also consistent adherence to prescribed regimens. However, data on how different treatment regimens and adherence levels influence glycemic control in local populations are limited. Objective This study aimed to evaluate the impact of different medication regimens and adherence levels on glycemic control, as measured by glycated hemoglobin (HbA1c) and fasting blood glucose (FBG) in T2DM patients at a tertiary care hospital in Lahore. Methods This retrospective study was conducted at Combined Military Hospital, Lahore, Pakistan, from May 2023 to May 2025, including 355 patients with T2DM. Patients were categorized by regimen type: Group 1 (oral therapy), Group 2 (injectable therapy), and Group 3 (combination therapy). Medication adherence was classified into three groups based on compliance with prescription refill data and follow-up documentation: High (≥80%), Medium (50-79%), and Low (<50%). Clinical and demographic data were extracted from electronic health records. Outcomes included HbA1c, FBG, and body mass index (BMI) at six months. Statistical analyses included chi-square for categorical outcomes and analysis of variance (ANOVA) for continuous outcomes. A p-value <0.05 was considered significant. Results By regimen, Group 3 (combination therapy) demonstrated the greatest reductions in HbA1c (-2.0% ± 1.3%), FBG (-54.3 ± 40.2 mg/dL), and BMI (-1.4 ± 1.5 kg/m²), compared to Group 2 (-1.7% ± 1.1%, -42.7 ± 34.0 mg/dL, -1.1 ± 1.3 kg/m²) and Group 1 (-1.3% ± 0.9%, -35.2 ± 27.4 mg/dL, -0.6 ± 0.9 kg/m²) (p < 0.05). By adherence, high-adherence patients achieved lower mean HbA1c (7.0% vs. 7.8% vs. 8.6%), FBG (140 vs. 160 vs. 180 mg/dL), and BMI (29.2 vs. 30.5 vs. 32.0 kg/m²) compared with medium- and low-adherence groups. Adverse events were more common in the injectable and combination groups. Conclusion Both the choice of antidiabetic regimen and patient adherence significantly influence glycemic control. Combination therapy was associated with the greatest improvements in HbA1c, FBG, and BMI, particularly in patients with high adherence. Interventions targeting adherence improvement are essential to optimize therapeutic outcomes in T2DM.