HbA1C’s predictive value for postoperative complications in cardiac surgery has been mixed. Studies did not account for HbA1C being over-read in anemic patients. This study proposes a novel way of using a ratio of HbA1C over hemoglobin (HH ratio). Retrospective recruitment of patients undergoing cardiac surgery was done with ethics approval. The primary objective of our study is to look for the correlation of HH ratio with 90-day(short-term) and 1-year(long-term) mortality. The secondary objective is to investigate its association with other adverse events. Statistical analysis was done using multivariable regressions and Cox proportional hazard models. Of the 974 patients recruited, 618 had a HH Ratio0.7. HH ratio of 0.5-0.7 and >0.7 was associated with 90-day mortality (HR5.12,p=0.033 and HR7.25,p=0.048 respectively) and 1-year mortality (HR4.53,p=0.028 and HR9.20,p=0.022 respectively). The higher HH ratio groups were also associated with increased length of stay(hours) in the intensive care unit(ICU)(p<0.001) and renal complications(p<0.001). Our study showed a positive association of HH ratio with 90-day and 1-year mortality and postoperative adverse outcomes in patients undergoing cardiac surgery. The HH ratio has the potential to be a new perioperative target.Copyright © 2020. Published by Elsevier Inc.