Objective: In this study, it was aimed to show the prognostic value of Ranson score + lactate level created by adding lactate to Ranson score in patients diagnosed with acute pancreatitis in the emergency department. Material and Methods:One hundred and sixty-three patients with acute pancreatitis were enrolled in this retrospective study. Demographic data, presentation time vital signs, biliary/non-biliary ethiology, Ranson score, hospitalisation clinic, length of hospitalisation, and 30-day mortlity rate data were noted. Ranson score and Ranson score + serum lactate levels were compared according to severity, prognosis and outcome.Results: Complication occurrence ratio was 8.6%. Totally, 160 (98.2%) patients were discharged and 3 (1.8%) patients died. Serum lactate level was significantly related with hospitalization of more than 10 days (p< 0.05). Correct prediction ratio of serum lactate level for complication occurrence during hospitalization was insufficient (p> 0.05). Ranson score and serum lactate levels were significantly correlated (p< 0.05). When we added lactate to Ranson score, correct outcome prediction ratio was significantly higher (p< 0.05). Serum lactate level and length of hospitalization and mortality were positively correlated (p< 0.05). According to ROC analyses, the cut-off level of serum lactate was 17.5 mg/dL for mortality prediction with 100% sensitivity and 75% specificity. Conclusion:Serum lactate level is an important parameter in predicting severity, prognosis and outcome of patients with acute pancreatitis. When serum lactate level is added to RS, better prediction ratios for prognosis and outcome are determined. Serum lactate level can be a useful parameter for emergency clinicians to plan the treatment strategy of acute pancreatitis patients in emergency medicine.