Haemoglobin A1c; glycated haemoglobin; glycosylated haemoglobin
To diagnose diabetes, to monitor a person's diabetes and to aid in treatment decisions. It can also be used to diagnose type 2 diabetes.
For the diagnosis of type 2 diabetes - only patients at high risk of undiagnosed diabetes should be tested. These are patients with either (i) a medical condition or ethnic background associated with high rates of type 2 diabetes, or (ii) an Australian type 2 diabetes risk (AUSDRISK) score of 12 or greater, placing them at increased risk of diabetes – (Reimbursed by Medicare).
For monitoring of diabetes - every 3-6 months - 4 times per year if glycemic goals are not met or when therapy plan has changed; at least 2 times a year if meeting treatment goals and under stable glycaemic control. Medicare reimburse four monitoring HbA1c tests per year. More frequent monitoring is needed in pregnancy, up to six tests in a 12-month period which is covered by Medicare
A blood sample drawn from a vein in the arm or from a fingerstick
As glucose circulates in your blood, some of it spontaneously binds to haemoglobin (the protein that carries oxygen in your red blood cells). This combination is called haemoglobin A1c (HbA1c). The amount of HbA1c formed is directly related to the amount of glucose in your blood. If your diabetes is not well controlled, your blood glucose levels are high, causing higher HbA1c levels. HbA1c levels do not change quickly since red blood cells live for 3-4 months. Because of this, the amount of HbA1c in your blood reflects the average amount of glucose in your blood during the last 2-3 months. The higher the level of glucose in the blood, the more glycated haemoglobin is formed.
Your blood may be drawn from a vein in your arm or, in some cases, a drop of blood from a finger-prick may be used.
No test preparation is needed.
The test for HbA1c can be used to diagnose diabetes and also indicates how well your diabetes has been controlled over the last few months. Even though you may have some very high or very low blood glucose values, HbA1c will give you a picture of the average amount of glucose in your blood over that time period. The result can help you and your doctor know if the measures you are taking to control your diabetes are working.
When your doctor suspects that you might have diabetes. After diabetes has been diagnosed Diabetes Australia recommends that for all individuals HbA1c is measured every 3-6 months. HbA1c may be measured more frequently in those who have just been diagnosed with diabetes, in those whose blood glucose remains too high, or when a treatment plan changes.
Diagnosis of Diabetes - HbA1c ≥6.5% (48 mmol/mol)
Prediabetes - 42–47 mmol/mol (6.0–6.4%) Even though Labelling people with an HbA1c value slightly under 48 mmol/mol (6.5%) with prediabetes is not recommended, the levels suggest a higher risk of developing diabetes.
In the past, HbA1c testing was only subsidised for monitoring blood glucose control in patients with established diabetes. A new Medicare item now permits the HbA1c test to be used for diagnosing diabetes. The new MBS item allows the test to be done once per patient per year, with an HbA1c of ≥6.5% (48mmol/mol) required for a diagnosis.
Using the HbA1c test is much simpler for patients than the fasting glucose test or the OGTT. This is because the test does not require fasting and can be done at any time of day.
The new test will not be suitable for a small number of patients with other illnesses including severe kidney and liver disease and certain blood disorders.
RCPA Manual: Haemoglobin A1c
NPS MedicineWise - Type 2 diabetes
Last Review Date: April 2, 2021