Objective During the course of COVID-19 disease, respiratory acidosis, respiratory alkalosis, metabolic acidosis and metabolic alkalosis may occur. This study aims to determine the acid-base imbalance by interpreting the blood gas of the patients with COVID-19 pre-diagnosis admitted to the emergency department. Method The study was planned retrospectively. Blood gas samples of all patients pre-diagnosed with COVID-19 were taken at first admission to the emergency department and analysed in the laboratory. According to clinical, radiological and microbiological evaluation, the patients were divided into two groups as COVID-19 (+) (n=171) and control group [(COVID-19 (-)] (n=129). Data analysis was conducted using SPSS version 19.0. p<0.05 was accepted for the level of statistical significance. Results In the control group, normal blood gas levels were observed more frequently than in the COVID-19 (+) group (p <0.05). Ionized calcium and potassium levels in blood gas were found to be lower in the COVID-19 (+) group than in the control group (p <0.05). Conclusion It is extremely important to take blood gas samples from the patients with COVID-19 pre-diagnosis in terms of guiding the treatment to be conducted in the emergency department.