Determinants, Barriers and Outcomes of Treatment and Behavioural Adherence in Patients with Type II Diabetes on Insulin Therapy: A Narrative Review

Abstract

Insulin is still important for many adults with type 2 diabetes (T2D), but in the real world, people often miss, miscalculate, or stop taking their doses, which can lead to high blood sugar levels and more healthcare visits. The current narrative review integrated determinants, alterable obstacles, and clinical and health-economic outcomes related to insulin adherence and persistence in adults with T2D undergoing insulin therapy. Seven databases were examined; 26 peer-reviewed empirical studies were incorporated and synthesized through SANRA-informed narrative techniques, reflexive thematic analysis, and theory-guided integration utilizing the Health Belief Model and Theory of Planned Behavior. There were six interrelated mechanisms: cognitive–motivational appraisal and psychological insulin resistance; capability and self-regulation (skills, self-efficacy, SMBG); routine disruption and regimen complexity driving omission, mistiming, and miscalculation; provider relationship and structured follow-up as social influence and accountability; system-level affordability and treatment design shaping persistence; and consistent links between adherence/persistence and better HbA1c/CGM outcomes with lower utilization and costs, while digital tools often improve glycemia through titration support and less clinical inertia. Different ways of measuring adherence, such as self-report, claims, and connected-device dosing, show that adherence is often based on the quality of the dose, not just the number of doses. Determinant-matched interventions that include counseling, technical training, making things easier, and protecting access are needed.

Keywords: Insulin adherence, persistence, type 2 diabetes, psychological insulin resistance, self-efficacy, regimen complexity, dose omission, dose mistiming, telemonitoring, health-economic outcomes