Background <p>Preoperative oral carbohydrate loading (POCL) has shown benefits in non-diabetic patients, but its use in patients with diabetes remains controversial. Concerns about potential hyperglycemia and adverse outcomes have led to conflicting evidence and varied clinical practices.</p> Objective <p>To assess the impact of POCL on clinical outcomes after surgery in patients with diabetes.</p> Methods <p>This retrospective study analyzed 679 patients with diabetes undergoing elective surgery from 2020 to 2023, divided into POCL and fasting groups. After 1:1 propensity score matching (PSM), 410 patients were analyzed. Primary outcomes included postoperative blood glucose levels; secondary outcomes were including glycemic variability, pulmonary infections, hospital stay length, and costs.</p> Results <p>After PSM, POCL was associated with significantly lower blood glucose levels on the first postoperative day compared to the fasting group (11.03 [9.43–12.77] vs. 11.37 [9.77–13.20], <i>P</i> = 0.045). No significant differences were observed in glycemic variability. POCL patients demonstrated shorter postoperative hospital stays (5.10 [3.00-7.70] vs. 5.90 [3.80–8.50], <i>P</i> = 0.022). Multivariate analysis revealed that POCL independently predicted reduced hospitalization costs (β=-3417.49, 95% CI [-6358.52, -476.46], <i>P</i> = 0.023) and shorter hospital stays (β=-1.21, 95% CI [-1.83, -0.60], <i>P</i> &lt; 0.001). Higher ASA scores and longer surgical durations were associated with increased costs, while prolonged surgeries correlated with greater pulmonary infection risk (OR = 1.005, 95% CI [1.003–1.008], <i>P</i> &lt; 0.001).</p> Conclusion <p>Despite previous concerns, POCL appears to be associated with lower early postoperative blood glucose levels, shorter hospital stays, and reduced costs in patients with well-controlled diabetes (HbA1c &lt; 7.5%). It may be a safe and effective perioperative strategy for this specific population, though individualized assessment remains essential.</p>