Background: Complications increase treatment costs of diabetes mellitus (DM). An adequate metabolic control of the disease could reduce these costs. Aim: To evaluate the costs of medical care for a cohort of patients with DM, according to their degree of metabolic compensation. Material and methods: All diabetic patients attended in a regional hospital from 2005 to 2010 were analyzed. A correlational study between costs of individual healthcare and levels of glycosylated hemoglobin (HbA1c), was performed in a series of annual cross-sectional measurements. Results: The study comprised 1,644 diabetic patients. During the study period the average cost of healthcare per patient increased from $878,000 to more than $1,000,000 Chilean pesos (CLP) during the study period. The percentage of patients with HbA1c levels below 7.0% varied between 43.0% and 54.9%. Costs for patients with HbA1c levels between 7 and 8.9% were 1.3 to 1.5 times greater. For the group of patients with HbA1c levels between 9 and 10.9% the costs increased 1.4 to 1.6 times. For patients with HbA1c levels greater than 11.0%, healthcare costs doubled. Conclusions: Healthcare expenditure varied according to metabolic control, which is consistent with international findings. This study was limited by its selected population, incomplete information on health expenditures, and the inclusion of only direct costs to the health system. If all patients would achieve metabolic compensation, the yearly savings would be CLP $308,000,000 (or USD $657,000).Background: Complications increase treatment costs of diabetes mellitus (DM). An adequate metabolic control of the disease could reduce these costs. Aim: To evaluate the costs of medical care for a cohort of patients with DM, according to their degree of metabolic compensation. Material and methods: All diabetic patients attended in a regional hospital from 2005 to 2010 were analyzed. A correlational study between costs of individual healthcare and levels of glycosylated hemoglobin (HbA1c), was performed in a series of annual cross-sectional measurements. Results: The study comprised 1,644 diabetic patients. During the study period the average cost of healthcare per patient increased from $878,000 to more than $1,000,000 Chilean pesos (CLP) during the study period. The percentage of patients with HbA1c levels below 7.0% varied between 43.0% and 54.9%. Costs for patients with HbA1c levels between 7 and 8.9% were 1.3 to 1.5 times greater. For the group of patients with HbA1c levels between 9 and 10.9% the costs increased 1.4 to 1.6 times. For patients with HbA1c levels greater than 11.0%, healthcare costs doubled. Conclusions: Healthcare expenditure varied according to metabolic control, which is consistent with international findings. This study was limited by its selected population, incomplete information on health expenditures, and the inclusion of only direct costs to the health system. If all patients would achieve metabolic compensation, the yearly savings would be CLP $308,000,000 (or USD $657,000).