Glycosylated haemoglobin (HbA1C) is a variant of haemoglobin bound to glucose and its ratio roughly represents the average blood glucose over the last three months. Values above 6.5% are considered highly suspicious for diabetes and is the most useful tool for monitoring glycaemic control. However, a single measurement is usually not sufficient to make a definitive diagnosis. Further tests are usually required and should be ordered by your doctor.