Introduction: Diabetes mellitus type 2 (DM2) is a heterogeneous group of disorders, characterized by varying degrees of insulin resistance, impaired insulin secretion and an increased concentration of glucose in the blood. DM2 is responsible for the structural and functional alterations of the cardiac muscle in the presence or absence of coronary artery disease (diabetic cardiomyopathy). Modern diagnostic testing of people with diabetes includes echocardiography and ergospirometry, which is important in the diagnosis of diabetic cardiomyopathy, as well as in the evaluation and treatment of this disease. Aim: To assess the functional capacity of patients with DM2, who have good glycemic regulation and preserved systolic function and to compare the value of the maximum (peak) oxygen uptake (peakVO2) with the values measured in the control group of healthy subjects. Material and methods: The prospective study included 30 patients (15 with and 15 without DM2), of both sexes, under the age of 55, with preserved systolic function, in whom anthropometric parameters, laboratory analysis, echocardiographic and cardiopulmonary exercise testing parameters were measured. The obtained data were processed statistically, and Pearson's correlation coefficient were used for determining the correlation. Results: Statistically significantly higher mean values of peak oxygen uptake and maximal oxygen pulse were found in the control group, while blood glucose levels and systolic blood pressure at rest were significantly lower. The slope of carbon dioxide equivalent was steeper in the group of patients with DM2. There were no significant differences in the structural and functional echocardiographic parameters between the groups. Conclusion: Patients with type 2 diabetes mellitus have lower functional capacity, expressed by peak oxygen uptake during exercise, even with good glycemic control. These changes in the functional capacity precede manifest complications, regarding structural and functional changes in the myocardium
