Carbohydrate Loading in Type 2 Diabetes Mellitus

The goal of this clinical trial is to learn the effects of preoperative carbohydrate loading on perioperative blood glucose levels and insulin resistance in type 2 diabetes mellitus undergo elective surgery. The main questions it aims to answer are: * Does carbohydrate loading affects perioperative blood glucose and insulin resistance in type 2 diabetes mellitus patients undergo surgery? * How are the incident of perioperative hyperglycemia and hypoglycemia between subjects who receive placebo compared with subjects who receive carbohydrate loading * How are the hyperglycemia-related complications comparison between two groups? Researchers will compare the carbohydrate loading intervention to placebo (regular drinking water with zero-calorie sweetener) to see the effects of carbohydrate loading to blood glucose levels and insulin resistance (by HOMA-IR value) Participants will: * randomized to carbohydrate loading (CHO) group or placebo * checked for preoperative, intraoperative, postoperative blood glucose, and preoperative and postoperative insulin level * evaluated for any hyperglycaemia-related complications