This prospective, observational study evaluates whether serum bicarbonate HCO3 levels can predict enteral nutrition intolerance (EFI) in adult ICU patients.Objective: To determine if lower HCO3 levels correlate with the development of EFI.Design: A 12-month study involving 70 participants at Sultangazi Haseki Training and Research Hospital.Methodology: Patients starting enteral nutrition within 48 hours of admission will be monitored for 72 hours. Daily HCo3 pH, and lactate levels will be recorded from routine morning blood draws.Hypothesis: Lower bicarbonate levels are an independent predictor of EFI development in critically ill patients.