HbA1c, or glycated haemoglobin, is a blood test that measures the average blood glucose levels over the preceding two to three months by assessing the percentage of haemoglobin that is glycated. It is crucial in the management of diabetes, as it helps evaluate long-term glycaemic control and guides treatment decisions. Elevated HbA1c levels are associated with an increased risk of diabetes-related complications, such as neuropathy and cardiovascular disease.