Exposure to wild mushrooms can lead to serious toxicity and death. It is accepted that patients who ingest potentially lethal mushrooms typically develop toxicity signs after six hours. However, clinical manifestations of poisoning that occur less than six hours after ingestion do not exclude the potential for life-threatening toxicity, especially when more than one type of mushroom has been eaten. Whereas there are not any clinical parameters that help to establish the severity of mushroom poisoning. In this study, we aimed to determine the relationship of serum glucose/potassium ratio and the clinical severity of mushroom poisoning cases.This is a retrospective study which includes the mushroom poisoning 510 cases between the years 2007 - 2018. Data consisted of age, gender, clinical history of mushroom poisoning including time from consumption to first symptoms, date of presentation, discharge time and laboratory results including complete blood cell count, biochemistry tests for liver and renal function, and coagulation profile. Patients included in this study were classified as mild-moderate and severe mushroom poisoning groups according to laboratory and clinical characteristics. Glucose, BUN, Creatinine, ALT, AST mean values and glucose/potassium ratio were significantly higher in the clinically severe group patients (p=0.008, p=0.01, p=0.039, p=0.037, p=0.046 and p=0.036 respectively). The sensitivity, specificity and area under curve for glucose/potassium ratio were as follows; 0.68, 0.57 (AUC %95CI) was 0.0647. Glucose/potassium ratio can predict the severity in mushroom poisonings according to our results which can helpful by management in mushroom poisonings as a laboratory result.