Background <p>Maintaining optimal glucose control is critical for postoperative care cardiac surgery patients. Continuous glucose monitoring (CGM) in this setting remains understudied. We evaluated the efficacy of CGM with a specialized titration protocol in cardiac surgery patients with type 2 diabetes (T2D) and prediabetes.</p> Methods <p>In this randomized-controlled trial, 54 cardiac surgery patients were randomized one day post-surgery, with 27 CGM and 25 point-of-care (POC) patients completing the study. The CGM group used Dexcom G6 with a CGM-specialized titration protocol, while the POC group used standard monitoring with blinded CGM. The primary outcome was time-in-range (TIR) 100–180&#xa0;mg/dL for 7&#xa0;days post-surgery. Secondary outcomes included various glycemic metrics and surgical outcomes. Multiple comparison adjustments were performed using false-discovery-rate (FDR).</p> Results <p>Thirty-one (59.6%) had diabetes and 21 (40.4%) had prediabetes. While TIR 100–180&#xa0;mg/dL showed no difference (74.7% vs. 71.6%, FDR-adjusted <i>p</i> = 0.376), the CGM group demonstrated improvements in TIR 70–180&#xa0;mg/dL (83.8% vs. 75.8%, FDR-adjusted <i>p</i> = 0.026), time-in-tight-range (TITR) 100–140&#xa0;mg/dL (46.3% vs. 36.3%, FDR-adjusted <i>p</i> = 0.018), and TITR 70–140&#xa0;mg/dL (55.3% vs. 40.5%, FDR-adjusted <i>p</i> = 0.003). Both groups maintained very low rates of time below range (&lt; 70&#xa0;mg/dL: 0.03% vs. 0.18%, FDR-adjusted <i>p</i> = 0.109). The CGM group showed lower postoperative atrial fibrillation (AF) (18.8% vs. 55.6%, FDR-adjusted <i>p</i> = 0.04999).</p> Conclusion <p>While the primary outcome was not achieved, CGM with a specialized titration protocol demonstrated safe glycemic control with improvements in TIR 70–180&#xa0;mg/dL and TITRs in cardiac surgery patients with T2D and prediabetes. The observed reduction in postoperative AF warrants further investigation.</p> Trial Registration <p>ClinicalTrials.gov NCT06275971</p> Graphical Abstract <p></p>