IntroductionClinical inertia is a lack of treatment intensification despite a failure to achieve appropriate targets using a current management strategy. Research focusing on the clinical inertia in type 2 diabetes mellitus (T2DM) remains scant. This study aimed to investigate factors associated with clinical inertia among patients with T2DM.Material and methodsThis observational study was conducted in a tertiary teaching hospital using medical records. T2DM patients attending the outpatient clinic between 1 January 2017 and 31 December 2017 were included. Failure to intensify the diabetes treatment of the participants was assessed. For this study, clinical inertia was defined as any T2DM patient event with an glycated haemoglobin (HbA<sub>1c</sub>) of ≥ 7.00% with no treatment intensification at the index date, or in a subsequent prescription written within the study time limits. Logistic regression analysis was used to determine associated factors.ResultsOf 5756 T2DM outpatients, 994 patients were enrolled in this study, with 26.2% of patients presenting clinical inertia. This study found that factors associated with lower clinical inertia were the use of insulin, HbA<sub>1c</sub> level at the index date, lower number of antidiabetic drugs used, and treatment by specialists (all p-value < 0.05).ConclusionsClinical inertia is a problem of T2DM treatment. Strategies should be developed to decrease this problem.