HbA1c & blood glucose control (summary)

The bloodstream contains red blood cells. These special cells carry oxygen around the blood. They do this using a protein called haemoglobin. Glucose can also stick to this protein. When it does, it is called ‘glycated haemoglobin’ (HbA1c).

Red blood cells normally live for 8-12 weeks before they are replaced by new ones. Because of this, measuring HbA1c allows you and your doctor to see how well your blood sugar levels have been controlled over that 8–12-week period.

If your sugar levels are persistently high, your HbA1c level will be high.

What levels should HbA1c be?

• HbA1c levels are usually below 41 mmol/mol (4-5.9%) in people who do not have diabetes.
• HbA1c levels are usual 48 mmol/mol (6.5%) or above in people with diabetes.

How is HbA1c tested?

Blood samples for testing HbA1c are most often taken from a vein in your arm with a needle (this is called a venous sample).

HbA1c readings are different to the finger prick tests you may take. Finger prick tests are there to show you what your blood glucose level is at that very moment in time.

You may also do what is called a ‘fasting’ blood glucose test. This is to show you what your blood glucose levels are like when you have not had anything to eat for 8-10 hours. This test can be done using blood taken from a finger prick.