This blood test measures the amount of glycated haemoglobin (HbA1c) in the blood. Glycated haemoglobin (HbA1c) is made when the glucose (sugar) in your body sticks to your red blood cells. As the lifespan of a red blood cell is 2-3 months, measuring HbA1c is an excellent way to measure the average amount of glucose in your blood during the 2-3 months before the sample was taken.