Comprehensive Complication Index

The goal of this multi-center, pragmatic, randomized controlled trial is to assess the effectiveness of continuous glucose monitoring (CGM) compared with conventional monitoring in enhancing surgical outcomes for diabetic patients. The main questions it aims to answer are: * To assess the effectiveness of CGM compared with conventional monitoring in reducing the comprehensive complication index (CCI) for patients with diabetes or impaired glucose tolerance (IGT) within 30 days after surgery. * To analyze the impact of different age groups, types of surgery, preoperative levels of HbA1c, and preoperative 24h glycemic variations on the improvement of surgical outcomes under the CGM model. Participants will receive CGM prescribed by the attending physician for at least 6 hours before surgery. Glucose monitoring should be continued until the 7th day after surgery or discharge. The investigators will compare conventional monitoring group to see if CGM could reduce the CCIs for patients with diabetes or impaired glucose tolerance within 30 days after surgery.