Background: Despite the wide variety of pathologies mandating open heart surgeries, most of the available guidelines on perioperative glycemic control in cardiac surgery are based on coronary artery bypass graft surgery (CABG). Aim of study: In this retrospective study, we aimed to compare the postoperative insulin doses in type-2 diabetic patients, regardless of whether the surgery was for ischemic heart disease (IHD) or another cardiac pathology, thereby facilitating future predictions and appropriate adjustments to insulin dosing. Methods: We included 370 type-2 diabetes patients who had open heart surgery in Cairo, Ain-Shams and Fayoum University hospitals throughout the previous five years, beginning in January 2021. The perioperative glycemic status and the required postoperative insulin dosage were extensively monitored and studied after the patients were divided into two equal groups: The CABG group and the non-CABG group. Results: Random blood sugar levels in the CABG group were significantly higher (165.7 ± 86 vs. 139.5 ± 75 mg/dl), which demands significantly higher insulin doses (2.84 ± 1.37 vs. 2.11 ± 1.26, P value < 0.001) for strict glycemic control through the first 3 days in the post-operative intensive care unit (ICU). Additionally, the maximal insulin dose was significantly higher in the CABG group (26.4 IU vs. 8.26 IU, P value < 0.001). Conclusion: Diabetic candidates for CABG are at higher risk for postoperative disturbed glucose levels and need for higher doses of insulin therapy.