What is HbA1c and what does it measure?
Haemoglobin (known as Hb) is present in the red cells of everybody's blood (it is the Hb of HbA1c). This is what makes your blood red. Glucose sticks to the haemoglobin in the red blood cells to give what is known as HbA1c. This happens by way of a complicated chemical reaction. The more glucose there is in the blood, the more glucose is attached to the haemoglobin. The amount of haemoglobin in your red cells with glucose attached is a good indication of the average glucose levels in your blood over the previous six to eight weeks. Your doctor will use the HbA1c results to monitor how well your diabetes is controlled.

What does it not measure?
The HbA1c test is not a measure of the blood glucose at a moment in time - as you get when you test your blood using your own blood glucose meter. Your home blood glucose monitoring allows you to track your blood glucose level at different times of the day. In contrast, HbA1c takes a long-term measure of your blood glucose control and expresses it in a different way.

Why measure HbA1c?
The HbA1c test tells you and your doctor what your blood glucose control has been and whether you are on target to keep your risk of developing the complications of diabetes as low as possible. The better your blood glucose control, the less chance there is of you developing the complications of diabetes.

How often is HbA1c measured?
How often HbA1c is measured is usually decided by your doctor. This will depend on many factors, including the type of diabetes you have and the way you have been managing your diabetes.

What are the current HbA1c units and targets?
For many years the way of measuring HbA1c has been aligned to that used in the Diabetes Control and Complications Trial (DCCT). The test is known as HbA1c (DCCT) and the results are given as a percentage. Your doctor is likely to have agreed a specific HbA1c target value with you to suit your particular circumstances.

What is changing in regard to HbA1c?
Laboratories in Ireland are about to change the way HbA1c results are reported. The International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) has put in place a new reference measurement system for the worldwide standardisation of HbA1c. This will make comparing HbA1c results from different laboratories and clinical research trials throughout the world much easier. These developments are supported by the international diabetes organisations. The new name for the test will be HbA1c (IFCC).

What are the new HbA1c (IFCC) units?
The HbA1c (IFCC) results will be reported in new units called mmol/mol (pronounced "millimoles per mole") rather than as a percentage, %. The range of HbA1c values in people without diabetes will be 20 to 42 mmol/mol. For people with diabetes the target levels will generally be a little higher and will be set by your medical team, usually in agreement with you.

How will the HbA1c results change?
The HbA1c (IFCC) results will be very different from the familiar HbA1c (DCCT) results, but the test will still give you the same basic information about what your glucose control has been over the last six to eight weeks. The following short table gives some examples of how the results compare.

The fact that the HbA1c (IFCC) result is higher does not mean there has been more glucose in your blood or that your diabetes was more poorly controlled. It is just a different way of expressing the same level of diabetes control. The HbA1c (IFCC) numbers are very different from blood glucose values which are similar to the reading you obtain with your meter and this will reduce the risk of you confusing the results of both of these measurements.

When will this change happen?
From 1st July 2010, all HbA1c results in Ireland will be given in the familiar HbA1c (DCCT) % format and in the new HbA1c (IFCC) mmol/mol format. So, for example, the report carrying your HbA1c result might read as follows: HbA1c (IFCC) 53 mmol/mol HbA1c (DCCT) 7.0%

The dual reporting of the HbA1c (DCCT) results alongside the new HbA1c (IFCC) results will continue until the end of 2011. It is likely that you will only have three or four HbA1c measurements made during the period of dual reporting so it is important that you become youraccustomed to the HbA1c (IFCC) numbers from early on. If you have any questions or concerns about these important changes, please ask doctor, diabetes nurse specialist, practice nurse or another member of your healthcare team to assist you.