Medication adherence assessed by the 8-item Morisky Medication Adherence Scale (MMAS-8) among patients with type 2 diabetes mellitus in Vietnam: A systematic review and meta-analysis

This systematic review and meta-analysis aimed to analyze the pooled medication adherence rate and identify factors associated with medication adherence among patients with type 2 diabetes mellitus in Vietnam, as assessed by the 8-item Morisky Medication Adherence Scale (MMAS-8). The protocol was registered on PROSPERO and conducted in compliance with the PRISMA 2020 statement. A literature search was conducted up to March 20, 2026, across seven electronic databases, Google Scholar, and 48 pharmaceutical journals. Study quality was evaluated using the Newcastle-Ottawa Scale (NOS), potential publication bias and small-study effects was evaluated using Egger’s test for funnel plot asymmetry, and the certainty of evidence was rated using the GRADE approach. Out of 2,109 initial records, 45 cross-sectional studies (comprising 13,728 patients) met the inclusion criteria. Meta-analysis using a random-effects model showed that the pooled medication adherence rate was 75.5% (95%CI: 70.6%-79.8%) (using a cut-off score of ≥ 6). Therapeutic regimens and interactions with healthcare professionals were frequently highlighted as factors potentially associated with medication adherence. The medication adherence rate measured by MMAS-8 among type 2 diabetes patients in Vietnam was relatively high, though the certainty of the current evidence remains very low. Reducing treatment burdens and strengthening health education interventions in clinical practice are essential to optimizing therapeutic outcomes.