AIMS: Assess the complexity of pharmacotherapy in diabetes mellitus in a basic health unit and investigate possible correlations with biochemical and pressure variables. METHODS: It is study observational, descriptive, cross-sectional study that included all patients with a primary diagnosis of type 2 diabetes and a prescription filled with at least one oral antidiabetic agent. The quantification of the complexity of the therapeutic regimen was performed according to the complexity index of the pharmacotherapy; and it was correlated with variables of the biochemical profile: capillary glycemia, creatinine and glomerular filtration, and pressure systolic and diastolic blood pressure, using the Spearman correlation analysis. RESULTS: The median of the complexity index of pharmacotherapy was 9.42±0,48 points, being more prominent in section B (5.03±2.57). The index was correlated with capillary glycemia (rho=0.538), systolic blood pressure (rho=0.520), creatinine (rho=-0.406) and glomerular filtration (rho=0.566). This correlation was directly proportional to the increase in capillary glycemia (p<0.01), systolic blood pressure (p<0.01) and glomerular filtration (p<0, 01), and inversely proportional to creatinine (p<0.05). CONCLUSIONS: Our findings revealed that polypharmacy in diabetes mellitus contributed to the generation of pharmacotherapy complexity, resulting in non-adherence to the prescribed treatment and consequently contributing mainly to the lack of glycemic and pressure control.