Objective: To investigate the effect of glucose-insulin-potassium (GIK) infusion on erythrocyte antioxidant enzyme activity levels during therapy and post-therapy in patients with dilated cardiomyopathy (DCM). Methods: Forty-one patients with DCM were enrolled in the present study. GIK solution (50 U of insulin in 500 mL of 30% glucose, plus 60 mmol/L KCl), in addition to the standard treatment, was administered by 24 h infusion in 28 patients (GIK group). In the remaining 13 patients (control group), 0.9% NaCl solution was administered. Venous blood samples from all patients were collected at baseline, during therapy (2 h, 8 h, 12 h and 24 h after baseline) and after therapy (48 h after baseline). The activity levels of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSHP) were measured. Results: In the GIK group, SOD values showed a significant increase at 24 h and 48 h compared with baseline and 2 h values (P<0.05). An increasing trend in CAT activity was observed during and after GIK infusion compared with baseline (0 h) values. However, these differences were not statistically significant (P>0.05). With regard to GSHP activity, no significant change was found in the GIK group during follow-up (P>0.05). In the control group, SOD, CAT and GSHP activity levels measured during and after therapy were found to be similar to those measured at baseline (P>0.05). Conclusion: Administration of GIK solution, in addition to standard therapy, in patients with DCM may improve the metabolic scope of the disease by reducing myocardial oxidative stress. © 2008 Pulsus Group Inc. All rights reserved.