If you are a person living with diabetes, you may well have heard the term HbA1c. It is an abbreviated name for a form of haemoglobin, the protein in the blood cells, which transports oxygen. HbA1c is also called haemoglobin A1c or just A1c.
What does it have to do with diabetes?
When sugar is processed by your body, glucose entering the bloodstream is naturally attracted to the haemoglobin and combines with it to form HbA1c. The volume of glucose that attaches to the haemoglobin protein is in direct proportion to the overall volume of sugar present in your body at the time of measurement.
Therefore, the amount of HbA1c in your blood is used as an indicator of average blood sugar levels (plasma glucose concentration) in the last 90 days[1].
How is it measured?
A regular blood test is routinely performed to establish HbA1c levels in people who have Type 1 and Type 2 diabetes mellitus, to show how well the plasma glucose concentration is being controlled. The higher the levels of HbA1c detected in the blood, the higher the concentration of blood sugar, with a greater risk of developing additional diabetes-related complications. HbA1c tests can also help to identify people at risk of diabetes or pre-diabetes, based on their blood sugar concentrations, and should be carried out at least once a year. You may be tested more often if, for example, your doctor wishes to monitor your condition more closely or has prescribed changes to your medication.
Why are there two types of test?
It is important to remember that blood glucose levels can be in a state of constant flux, changing literally every minute as you eat, drink and exercise. You need to test for blood glucose levels throughout the day to assess what impact is made on your blood sugar by different types of food and drink – but this is a time-specific spot measurement of the blood glucose concentration only at that exact moment. Longer-term testing averages these levels over the life-cycle of the red blood cells (8-12 weeks) and is usually a regular blood sample taken from the arm. It assesses how well you are keeping diabetes under control generally, and whether your daily routine is helping to cope with the condition.
How much HbA1c should I have?
A generalised target level for people with diabetes is 6.5%, or 48 mmol per mol, where the normal level for people without diabetes is below 6% or 42 mmol per mol.
However, every individual person with diabetes should consult their doctor for more specific measurements and a personalised target, as each person’s target concentration must take into consideration their daily activities and lifestyle, and risk of hypoglycaemic stress (low blood sugar).
Does reducing HbA1c help avoid diabetes-related complications?
Both the UK Prospective Diabetes Study and the Diabetes Control and Complications Trial in the US concluded that reducing HbA1c in Type 1 or 2 diabetes sufferers by 1%, or 11 mmol per mol lessened the risk of such microvascular complications as nerve, eye and kidney diseases.
[1] 90 days is the natural lifespan of a red blood cell