Objectives: To investigate glycemic control in outpatient clinics at a university hospital, as well as to correlate HbA1c with fasting glucose and post-prandial glycemia, in order to assess which variable best correlates with an HbA1c. Methods: This is a descriptive cross-sectional study, with data that were collected from electronic medical records, from the random consultation of the medical of the blood glucose measurement. To check glycemic control, the parameters defined by the Brazilian Diabetes Society (2017-2018) were used: fasting glucose <100 mg / dL, HbA1c <7% and postprandial glucose <160 mg / dL. A statistical analysis was performed with the aid of the SPSS® program (version 13.0), adopting p <0.05 as the level of statistical significance. Results: 250 medical records were applied, with the average age of the participants being 60.1 ± 12.9 years (87 men and 163 women). A fasting glycemia was altered beyond the recommended in 80.8% of the individuals evaluated, HbA1c in 45.2% of the cases and 66% of the participants in the study possessed postprandial glycemia in addition to the recommended goals. The correlation between HbA1c/fasting blood glucose (rs= 0.74) and HbA1c/postprandial blood glucose (rs = 0.60) was, respectively, strong and moderate. Conclusions: With this study, it was possible to verify that a significant portion of the limits of use did not have good glycemic control. The correlation between fasting glucose and HbA1c confirmed that HbA1c is the best parameter for monitoring blood glucose levels in diabetes mellitus. In addition, the fasting blood glucose / HbA1c correlation showed greater strength in the postprandial blood glucose / HbA1c correlation.