Literature Search: 
A comprehensive literature search was done on PubMed, SCOPUS, Embase, Cochrane database, google scholar and Ovid to identify the articles that discussed the HbA1c, glycated haemoglobin and its implications on perioperative cardiac surgery outcomes. Key words used were ‘HbA1c’ ‘Glycated haemoglobin’ ‘Cardiac Surgery’ ‘Haemoglobin A’ ‘HbA1c and outcomes’ ‘Diabetes’ ‘Diabetic correlation’. The search terms were used as key words and in combination as MeSH terms to maximize the output from literature findings. A staged literature search was done, whereby a separate literature search was performed for each section within this article and all the relevant studies were identified and summarized separately. If a paper is reporting on many aspects of the practice of HbA1C, then the results have been shared between different parts of this review. The relevant articles are cited and referenced within each section separately. No limits were placed on publication time or language of the article.