HbA1c Explained

Contents

• What is HbA1c?
• What does the HbA1c test tell us?
• How often should my HbA1c be measured?
• HbA1c results and target

What is HbA1c?

Glucose in the blood sticks to the red blood cells, making a substance called ‘glycated haemoglobin’, known as haemoglobin A1c or HbA1c for short.

Red blood cells live for about 8–12 weeks before they are replaced by new ones so the HbA1c test tells you how well your blood glucose has been controlled over the previous 8–12 weeks. The more glucose in your blood, the more HbA1c will be present, so the level reported will be higher.

What does the HbA1c test tell us?

The better your blood glucose control the less chance there is of you developing diabetes complications such as eye, kidney or nerve damage, heart disease or stroke. The HbA1c test may change if you have changed your diet, physical activity, weight or medication and is a way of measuring whether you are on target to keep your risk of complications as low as possible.

How often should my HbA1c be measured?

Blood glucose levels vary throughout the day and from day to day, but HbA1C gives an average of what the glucose is over a longer 2-3 month period.   HbA1c should be measured regularly but not too frequently. You will normally be tested every three to six months.

HbA1c results and target

It is important that you agree your own personal target with your diabetes care team, as different people will have different targets, depending on their individual circumstances.

For example, if you have had a lot of problems with low blood glucose levels and have had several hypoglycaemic episodes (‘hypos’), a higher target might be appropriate.

The HbA1C results will be expressed either in millimoles per mol (mmol/mol) or as a percentage (%). Table 1 shows how the results compare:

Table 1: Comparison of HbA1c results

For further information on blood glucose testing and HbA1c, see the resource here.