CONCLUSIONS AND RELEVANCE: Glycemic control significantly impacts morbidity and mortality in surgical patients. A total of 23% of patients were patients with undiagnosed prediabetes or diabetes, underscoring the importance of preoperative HbA1c screening for all patients. Both very low and very high HbA1c levels should be preoperatively addressed, with moderate control (HbA1c 7-8%, 53-64 mmol/mol) identified as optimal. Overall, these findings emphasize the need for personalized …