<![CDATA[Background: Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder requiring long-term pharmacological treatment and sustained self-management. Medication adherence is a critical determinant of glycemic control and therapeutic outcomes; however, suboptimal adherence remains a persistent challenge in outpatient diabetes care.. Method: This narrative review synthesized open-access evidence published predominantly between 2021 and 2026. Literature was identified through PubMed/MEDLINE, ScienceDirect, SpringerLink, Wiley Online Library, DOAJ, and Google Scholar, supplemented by reports from the World Health Organization, International Diabetes Federation, Indonesian Ministry of Health, and BPJS Kesehatan. The synthesis focused on evidence regarding medication adherence among outpatients with T2DM, determinants of non-adherence, and its implications for HbA1c, glycemic control, quality of life, and therapeutic outcomes. Results: The reviewed evidence indicates that adherence to antidiabetic medications remains suboptimal and is generally associated with poorer glycemic control. Non-adherence is influenced by multidimensional factors, including inadequate knowledge, medication beliefs, low self-efficacy, depressive symptoms, regimen complexity, polypharmacy, adverse effects, comorbidities, treatment costs, limited family support, medication accessibility, and healthcare-provider communication. Patient-centered interventions, particularly pharmacist-led counseling, regimen simplification, family engagement, and structured chronic disease management, demonstrate potential to improve adherence and clinical outcomes. Conclusion: Medication adherence should be routinely assessed as an integral component of T2DM management before treatment intensification. Multilevel, patient-centered, and health-system-supported interventions are required to address modifiable barriers and improve adherence, glycemic control, quality of life, and therapeutic outcomes]]>
