Background/aim: To investigate the protective role of intraoperative infusion of N-acetylcysteine (NAC), and excess fluid on liver injury and blood pH levels during laparoscopic sleeve gastrectomy. Materials and Methods: Forty-five consecutive patients who underwent laparoscopic sleeve gastrectomy for treatment of obesity between september 2016-june 2017 were randomized into three groups each with 15 patients: Group 1 (control group) was applied neither NAC intraoperatively, Group 2: 10 mg/kg intravenous NAC and 30 mL/kg fluid, and Group 3: 30 mg/kg NAC and 50 mL/kg fluid intraoperatively. The fluid was ringer lactate and normal saline in 1:1 ratio. Biochemical markers of liver function and metabolic acidosis were evaluated. Results: Blood levels of AST, ALT increased significantly with the operation (p<0.001). The increase in AST was significantly higher in Group 3 compared to Group 1 (p=0.046). HCO3 and pH were within normal range preoperatively, but significantly decreased indicating development of primary metabolic acidosis in all groups. The decrease in both HCO3 and pH was significantly less in Group 3 than Group 1 (p<0.05). Conclusion: Intraoperative infusion of 30 mg/kg NAC and 50 mL/kg fluid during laparoscopic sleeve gastrectomy may reduce liver injury and prevent metabolic acidosis, thus should be considered during surgical management of morbidly obese patients.