Objective To assess whether the blood lactate of patients with chronic obstructive pulmonary disease elevates more during the six-minute walk test. Methods This cross-sectional study included 29 individuals divided into three groups: control (n=10), mild chronic obstructive pulmonary disease (n=9), and moderate chronic obstructive pulmonary disease (n=10). Disease degree was classified according to the forced expiratory volume of the first second and Tiffeneau index obtained by recent spirometry. All patients underwent anthropometric and clinical assessment. Blood lactate was measured before and after three minutes of the six-minute walk test. The Kruskal-Wallis test compared the data obtained before and after the six-minute walk test, and Spearman’s correlation assessed the influence of some variables on blood lactate. The significance level was p<0.05. Results Although the patients with moderate chronic obstructive pulmonary disease had the worst performance in the six-minute walk test as they walked a smaller distance (403.3m) than the patients with mild chronic bstructive pulmonary disease (424.8m) and the controls (541.8m), they had higher mean blood lactate level (2.57mmol/L) than the patients with mild chronic obstructive pulmonary disease (1.46mmol/L) and the controls (0.9mmol/L). Conclusion Higher obstruction of the airways and its systemic repercussions resulted in significant metabolic limitation in patients with moderate chronic obstructive pulmonary disease, expressed by higher blood lactate level and smaller distance walked in the six-minute walk test.