Background Epileptic seizures (SZ) and postictal neurological deficits are common stroke mimics that challenge acute clinical decision-making, especially in emergency settings with limited diagnostic resources. MRI or EEG is often unavailable at initial presentation. We aimed to determine whether routinely available serum lactate levels could distinguish SZ from stroke based on information accessible immediately on hospital arrival. Methods We retrospectively reviewed 22,430 consecutive emergency department visits and analyzed 637 patients transferred by ambulance with suspected neurologic emergencies identified via keyword screening at the regional emergency call center. All patients underwent venous blood gas analysis and non-contrast CT on arrival. We evaluated whether serum lactate and other routine laboratory variables (pH, actual base excess, glucose, WBC count, platelet count, and PT-INR) correlated with final neurological diagnoses. Classification and Regression Tree (CART) analysis was used to identify cutoffs predictive of SZ. Results Age, pH, lactate, and actual base excess were significantly associated with final diagnoses. Lactate levels were significantly higher in SZ and subarachnoid hemorrhage groups than in other groups. For distinguishing SZ from ischemic stroke (infarction and TIA), CART analysis yielded a serum lactate cutoff of 4.05 mmol/L. Among patients with lactate ?4.05 mmol/L and age <59.5 years, SZ probability was 100%. A four-quadrant model combining lactate and age stratified SZ probabilities from 9.1% to 100%. The area under the ROC curve for lactate in distinguishing SZ from stroke was 0.800. Conclusions Serum lactate, when assessed upon emergency department arrival, may contribute significantly to differentiating seizures from acute ischemic stroke. A simple decision model using only lactate and age may aid in diagnostic stratification in neurologic emergencies-even in resource-limited settings where advanced imaging or EEG is not readily available. Registration None.