HbA1c Blood Test Explained
Your 3-month average blood sugar — the diagnostic test for type 2 diabetes in Australia. Normal range, IFCC vs DCCT units, MBS rebate, and what your result actually means.
The Short Answer
HbA1c (glycated haemoglobin) shows your average blood glucose over the past 2 to 3 months. In Australia, the diagnostic thresholds are clear: under 42 mmol/mol (6.0%) is normal, 42 to 47 mmol/mol (6.0 to 6.4%) is prediabetes, and 48 mmol/mol (6.5%) or higher on two separate tests is diabetes. No fasting required. Bulk-billed by Medicare for diagnosis in at-risk adults (MBS 66841) and for routine monitoring of established diabetes up to 4 times per year.
What HbA1c Actually Measures
Glucose in your bloodstream sticks to haemoglobin — the oxygen-carrying protein inside your red blood cells — in a slow, irreversible chemical reaction called glycation. The HbA1c test measures what percentage of your haemoglobin has glucose attached.
Because red blood cells live for about 120 days, the percentage of glycated haemoglobin gives a stable, time-averaged picture of blood glucose. Roughly half the result reflects glucose levels in the past 4 weeks, with the rest spread across the previous 8 to 12 weeks. That makes HbA1c much harder to game than a single fasting glucose test: you cannot simply skip breakfast and look healthy.
HbA1c was first standardised internationally in 2011, when Australia adopted the IFCC reporting system (mmol/mol). The older DCCT units (%) are still printed alongside because that is what most clinicians and patients are familiar with. Both numbers describe exactly the same blood result — they are just different scales.
Australian HbA1c Reference Ranges
These thresholds are set by Diabetes Australia, the RACGP and the World Health Organisation and are used by virtually all Australian pathology providers.
Normal
Average blood glucose in the healthy range. No evidence of impaired glucose handling. Recheck in 3 years if at average risk, sooner if family history.
Prediabetes
Glucose handling is starting to drift. About 1 in 3 people in this range will progress to type 2 diabetes within 5 years without intervention. Lifestyle changes can prevent progression in most cases.
Diabetes
Two HbA1c results at this level (or one with classic symptoms) confirm a diabetes diagnosis. Treatment usually starts with lifestyle plus metformin and is reviewed every 3 to 6 months.
Diabetes target (general)
For most adults with type 2 diabetes, the RACGP and Diabetes Australia recommend an HbA1c target around 53 mmol/mol (7.0%). Targets are individualised — tighter for younger patients with no complications, looser for older or frailer patients.
Severe hyperglycaemia
Reflects average glucose over 13 mmol/L for months. High risk of complications — eye damage, kidney damage, neuropathy, cardiovascular events. Needs prompt treatment intensification.
HbA1c Unit Conversion (IFCC vs DCCT vs Average Glucose)
If your report shows mmol/mol but you remember the old % numbers (or vice versa), this conversion table covers the range you are likely to encounter. The right column shows estimated average glucose (eAG) in mmol/L, which is what your blood sugar would average if you wore a continuous glucose monitor.
IFCC (mmol/mol)
DCCT (%)
Avg Glucose
31 mmol/mol
5.0%
5.4 mmol/L
37 mmol/mol
5.5%
6.2 mmol/L
42 mmol/mol
6.0%
7.0 mmol/L
48 mmol/mol
6.5%
7.8 mmol/L
53 mmol/mol
7.0%
8.6 mmol/L
64 mmol/mol
8.0%
10.2 mmol/L
75 mmol/mol
9.0%
11.8 mmol/L
86 mmol/mol
10.0%
13.4 mmol/L
How Often Should You Have HbA1c Tested?
No risk factors
Routine screening through the AUSDRISK risk assessment used in most Australian general practices.
Increased risk (family history, BMI over 30, gestational diabetes history, PCOS)
MBS item 66841 covers HbA1c annually for adults with risk factors documented by their GP.
Prediabetes (42 to 47 mmol/mol)
Lifestyle changes can return HbA1c to normal or prevent progression. Repeat to track response.
Established diabetes, stable
Two tests per year is the minimum standard of care for stable type 2 diabetes.
Established diabetes, treatment changes
Allows you to see the effect of new medication, insulin titration, or significant lifestyle change.
Pregnancy
Pregnancy changes red blood cell turnover, making HbA1c unreliable. Use the oral glucose tolerance test (OGTT) instead.
HbA1c Cost — Medicare and Private
MBS item 66841 — HbA1c diagnosis and monitoring
Bulk-billed by all major Australian pathology providers when ordered by your GP and the request meets one of these criteria:
- Diagnosis: once every 12 months in an adult with documented risk factors (AUSDRISK score, family history, obesity, PCOS, history of gestational diabetes, etc.)
- Monitoring: up to 4 times per 12 months in an adult with established diabetes
Private (no Medicare rebate)
If you order HbA1c through a self-request service like i-screen, MyHealth Lab, OneStop Pathology, or as part of a wellness panel, expect to pay $30 to $50 for HbA1c alone, or $80 to $200 as part of a broader metabolic panel.
When HbA1c is Misleading
HbA1c relies on red blood cells living and circulating normally for ~120 days. Anything that disrupts that — the cells dying earlier or haemoglobin behaving abnormally — can throw the result off.
Iron-deficiency anaemia — falsely high HbA1c
In iron deficiency, red blood cells live longer than normal and accumulate more glucose. Your HbA1c can read 5 to 10 mmol/mol higher than your true average glucose, sometimes pushing a non-diabetic person into the prediabetic range. Always check ferritin alongside HbA1c if fatigue is part of the picture.
Chronic kidney disease — falsely low HbA1c
In advanced kidney disease, red blood cell lifespan shortens and the bone marrow makes new ones faster. Younger red cells have less time to pick up glucose, so HbA1c reads lower than the true average. Doctors often use fructosamine or continuous glucose monitoring instead.
Haemoglobinopathies — result depends on the variant
Sickle cell trait, beta-thalassaemia trait, haemoglobin C, and other haemoglobin variants can interfere with the laboratory assay used to measure HbA1c. Some assays are affected, others are not. If your family origin includes Mediterranean, African, Middle Eastern, or South Asian backgrounds, mention this so the lab knows to use a non-interfering method.
Recent blood transfusion or blood loss
A transfusion floods your circulation with someone else's red cells. Significant blood loss followed by recovery brings in a wave of young red cells. Both situations make HbA1c unreliable for at least 3 months.
Pregnancy
Pregnancy increases red blood cell turnover, so HbA1c reads lower than the true average glucose. The oral glucose tolerance test (OGTT) between 24 and 28 weeks remains the standard for gestational diabetes in Australia.
How to Prepare
HbA1c is the easiest blood test in modern medicine to prepare for.
No fasting
Eat and drink normally. HbA1c reflects 3 months of glucose, so what you had for breakfast is irrelevant. This is one of HbA1c's biggest practical advantages over fasting glucose.
Take all medications
Including diabetes medications. The point is to see your average control on your current regime.
Time of day does not matter
Morning, afternoon, evening — all give the same HbA1c.
Mention recent illness or transfusion
A serious infection in the past month or any blood transfusion in the past 3 months can affect interpretation.
Frequently Asked Questions
What is a normal HbA1c level in Australia?
A normal HbA1c is below 42 mmol/mol (under 6.0% in older units). Prediabetes is 42 to 47 mmol/mol (6.0 to 6.4%), and diabetes is diagnosed at 48 mmol/mol or higher (6.5% or higher) on two separate tests.
What units are used for HbA1c in Australia?
Australian pathology labs primarily report HbA1c in IFCC units (mmol/mol) since 2011, with the older DCCT units (%) shown alongside for clinical familiarity. Both numbers describe the same blood result. For example, 48 mmol/mol equals 6.5%.
Does Medicare cover the HbA1c test?
Yes, but the rules differ for diagnosis versus monitoring. For diagnosing diabetes in someone at high risk, MBS item 66841 covers HbA1c every 12 months. For monitoring an established diabetic, HbA1c is rebated up to 4 times per year. Self-requested HbA1c outside these criteria is typically $30 to $50 private.
Do I need to fast for an HbA1c test?
No. HbA1c reflects your average blood glucose over the past 3 months and is not affected by what you ate that morning. You can have it taken at any time of day. This is one of the main advantages of HbA1c over a fasting glucose test.
Why does the HbA1c test cover 3 months?
HbA1c measures the percentage of haemoglobin in red blood cells that has glucose attached to it. Red blood cells live for about 120 days, so the test reflects average glucose exposure over that lifespan. The most recent 4 to 6 weeks contribute roughly half the result.
Can HbA1c be wrong?
Yes. HbA1c is unreliable in iron-deficiency anaemia (falsely high), recent blood transfusion, chronic kidney disease, haemoglobin variants like sickle cell or thalassaemia, and pregnancy. In these situations, doctors use fructosamine, continuous glucose monitoring, or a glucose tolerance test instead.
How quickly can my HbA1c improve?
A meaningful HbA1c change takes about 8 to 12 weeks because of the red blood cell lifespan. Lifestyle changes, weight loss, or new medication will not show their full effect until your next test 3 months later. The good news is that even modest improvements (10 to 15 mmol/mol) substantially reduce diabetes complications.
Related Reading
Track Your HbA1c Over Time
Upload every blood test you have ever had and SmarterBlood plots your HbA1c trend, flags whether you are heading towards or away from your target, and explains every other marker in plain English — in both mmol/mol and %.
This page provides general educational information about the HbA1c blood test in Australia. Diagnostic thresholds, MBS rules, and clinical guidelines change over time. SmarterBlood does not provide medical advice. Always discuss your individual results and treatment with a qualified healthcare professional.