Abstract: HbA1c is formed over a period of two to three months and reflects the glycaemic status of a patient over the past two to three months for this reasons HbA1C test has been used for diabetics followup and diagnosis. The relationship between HbA1c and average blood glucose is complex but has been studied by the Diabetes Control and Complications Trial (DCCT). A new internationally standardized method for reporting HbA1C has been developed by the International Federation of Clinical Chemistry (IFCC). This will report HbA1C in mmol per mol of hemoglobin without glucose attached. HbA1c has now been recommended by an International Committee and by the ADA (American Diabetes Association) as a mean to diagnose diabetes and as a screening test for persons at high risk of diabetes. Also, the International Diabetes Federation and American College of Endocrinology (ACE) recommend HbA1c values below 48 mmol moL–1 (6.5%). The 2010 American Diabetes Association Standards of Medical Care in Diabetes added the A1c 48 mmol moL–1 (6.5%) as another criterion for the diagnosis of diabetes mellitus.