Introduction: Evidence has demonstrated clinical or prescriptive inertia along with an increased prescription of insulin, causing a delay in the change of prescription.Objective: To determine the prescription pattern and clinical inertia of insulin use in the treatment of patients with type 2 diabetes mellitus (DM2) enrolled in a diabetes program at a primary health care institution of Cartagena, Colombia.Materials and methods: Pharmacoepidemiology study that addresses drug utilization based on data collected through a review of medical records of 331 patients with DM2, aged 18 and older, who had at least 6 months of control.Results: 64.4% of patients were treated with long-acting insulin analogues and 18.4% used insulin; 52.7% of the patients in which insuline use was required did not have a prescription of this drug.Conclusions: There is clinical inertia related to insulin prescription. Strategies should be implemented to overcome prescriptive inertia for people with DM2 in order to achieve therapeutic goals earlier and effectively prevent the development and progression of chronic complications.