Objetive: This study evaluated the results of treatment adherence scales in two cohorts of patients with diabetes mellitus treated either with human or analogue insulins.Methods: A cohort study was conducted in diabetes mellitus patients older than 18 that were being treated with human or analogue insulins. Two instruments were applied to each patient [medication possession ratio, Morisky-Green test] to evaluate treatment adherence.Results: A total of 238 patients, were included. The majority (69.4%) of the subjects had human insulin and 30.6% had insulin analogue prescriptions. Out of the total, 163 (68.5%) cases were classified as adherent to therapy, according to the type of insulin, as follows: 69.9% for conventional and 65.3% for analogues; without differences between the groups (CI95%:0.450–1.458). The adherence to treatment was more probable in patients with elementary-secondary education (OR:2.341; CI95%:1.199–4.568) and less probable for those in the age range of 31–45 years (OR:0.427; CI95%:0.187–0.971).Conclusions: The results of this study show that there are no significant statistical differences in adherence when comparing human with analogue insulin therapy. Strategies to improve treatment adherence are particularly important since they improve the clinical results.