ObjectiveTo evaluate the impact of a pharmaceutical intervention on treatment optimization in patients with type 2 diabetes mellitus. DesignBefore-after intervention study. SiteHealth centers of the Primary Care Department of Camp de Tarragona. ParticipantsPatients aged ≥ 18 years, diagnosed with type 2 diabetes mellitus and under treatment with antidiabetic drugs. InterventionsReview of pharmacological treatment for type 2 diabetes mellitus and issuance of proposals for its adequacy. Main measurementsDemographic and clinical variables were collected to assess the adequacy of antidiabetic treatment. A consensus meeting was arranged with the patients’ primary care physician to evaluate the proposals for improvement. The implementation of the proposals and the variation in postintervention glycemic control were assessed. ResultsA total of 907 patients (59% men) were included. A total of 782 proposals for intervention were made in 65.8% of the patients reviewed. Of the proposals, 43.5% corresponded to drug discontinuation, 16% to intensification of dosing and 12.6% to exchange for a therapeutic equivalent. Of the consensual proposals, 54.7% were implemented. HbA1c was reduced by 0.2% after the intervention (7.4 vs 7.2%). ConclusionsReview of the pharmacological treatment of patients with type 2 diabetes mellitus by a pharmacist or pharmacologist facilitates its optimization.