Background: Carbon monoxide (CO) poisoning is a major health problem associated with a high rate of severe morbidity and mortality. Aims: This study aimed to evaluate the validity of the serum glucose/potassium (Glu/K) ratio as a quick predictor of both early and delayed unfavorable outcomes following acute CO poisoning. Patients and methods: This prospective cohort study included 136 patients with acute CO poisoning admitted at Tanta Poison Control Center, Egypt, between January 2023 and June 2024. The serum Glu/K ratio was calculated for all patients. The primary outcome was a prediction of mortality. Secondary outcomes were the prediction of delayed neurological sequelae (DNS) within six months after CO exposure, the need for mechanical ventilation, and the need for hyperbaric oxygen. A receiver operating curve analysis was applied to test the performance of the Glu/K ratio in predicting acute CO poisoning outcomes. Results: The mortality rate was 12.5% of patients with acute CO poisoning. Meanwhile, 14.7% of patients developed DNS. Furthermore, mechanical ventilation was required in 16.9% of patients. An elevated Glu/K ratio was significantly associated with the severity of acute CO poisoning. At a cut-off value of >31.62, the Glu/K ratio demonstrated an AUC of 0.649 for predicting mortality. The Glu/K ratio was employed to predict DNS at a cut-off value of 33.10, with a sensitivity of 60.0%, a specificity of 82.76%, and an AUC of 0.692. Conclusions: Early Glu/K ratio may be an effective, reliable, and convenient laboratory predictor of mortality, DNS, and the need for mechanical ventilation in patients with acute CO poisoning.