BackgroundPreoperative carbohydrate loading is used to improve patients’ comfort and recovery, but evidence remains limited in diabetic patients. We tested the feasibility of a preoperative carbohydrate drink with supplemental insulin in diabetic patients for gastrointestinal surgery.MethodsAdult patients with type 2 diabetes mellitus who were scheduled for major gastrointestinal surgery were randomized to carbohydrate group (carbohydrate drink with supplement insulin selectively) or control group (clinical routine management). The primary outcome was the time to first flatus after surgery. Among secondary outcomes, subjective feelings of thirsty, hunger and fatigue were assessed with the Visual Analogue Scale (scores range from 0 to 100, where 0 indicate no discomfort and 100 the most severe discomfort) before and after surgery.ResultsA total of 63 patients were randomized. Time to first flatus did not differ between groups (median [95% CI], 40 hours [30, 50] in control group vs. 43 hours [37, 48] in carbohydrate group, hazard ratio [95% CI], 1.24 [0.74, 2.07], P = 0.411). Both pre- and postoperative subjective feelings of discomfort were all significantly lower in carbohydrate group than in control group (median difference from − 50 to 0; all P < 0.05). Patients with carbohydrate drink developed less intraoperative hypotension (40.6% [13/30] vs. 16.1% [5/31], P = 0.031) and postoperative nausea and vomiting within 24 hours (31.3% [10/32] vs. 9.7% [3/31], P = 0.034).ConclusionIn diabetic patients undergoing gastrointestinal surgery, preoperative carbohydrate loading with supplemental insulin selectively did not affect gastrointestinal recovery; but it improved perioperative comfort, and reduced intraoperative hypotension and postoperative nausea and vomiting.Trial RegistrationClinicalTrial.gov, NCT03204344; Registered July 2, 2017, https://clinicaltrials.gov/ct2/show/NCT03204344.