Comparative Analysis of Clinical Outcomes in Patients With Type 2 Diabetes Mellitus on Monotherapy Versus Combination Therapy

Type 2 diabetes mellitus (T2DM) is a highly prevalent metabolic disorder associated with substantial microvascular and macrovascular morbidity, necessitating effective and durable therapeutic strategies. Progressive pathophysiology involving insulin resistance, beta-cell dysfunction, and multisystem metabolic dysregulation limits the long-term effectiveness of single-agent therapy in many patients. This narrative review aims to compare clinical outcomes associated with antidiabetic monotherapy and combination therapy in individuals with T2DM, with emphasis on glycemic control, cardiovascular outcomes, metabolic effects, safety, adherence, and cost considerations. A comprehensive literature search of major electronic databases was performed to identify relevant studies published between 2015 and 2025, including randomised controlled trials, observational studies, real-world analyses, and systematic reviews involving adult T2DM populations. Evidence indicates that monotherapy remains appropriate in early disease stages and in patients with modest hyperglycemia, offering simplicity and favourable tolerability. Combination therapy demonstrates superior and more durable glycemic control through complementary mechanisms of action and is associated with improved cardiovascular and metabolic outcomes, particularly when agents with cardioprotective and weight-modifying properties are included. Safety profiles vary across therapeutic classes, with combination regimens requiring individualised selection to minimise adverse events and optimise adherence. Economic analyses suggest that higher initial costs for combination therapy may be offset by reduced complications and healthcare utilisation. Individualised treatment strategies integrating timely combination therapy support sustained metabolic control and improved long-term outcomes in T2DM.