Your HbA1c is a measure of how much sugar is attached to haemoglobin a protein inside the red blood cells.
The more sugar there is in the blood, the more will stick to haemoglobin, which increases your HbA1c level. Once it sticks, sugar remains on the haemoglobin for the life of the red blood cell, which is about three months, Therefore your HbA1c reflects the prevailing blood glucose levels over the preceding 2-3 months. It is shown as a percentage. For most people without diabetes, the normal range from is 4-6%.
The DCCT (a 10-year study that took place 1983-1993) showed that the risk of complications of diabetes increases as HbA1c increases. Your target HbA1c level should be agreed with your healthcare team and your therapy adjusted in order to help you to reach it. The general target currently prescribed is to have an HbA1c of less than 7.0 %. However, this should assessed in relation to your risk of severe hypoglycaemia, and other health factors.