Remember my dad from the cholesterol article? The one who rang me to confess he'd been put on a statin?
There was a second part to that conversation that I didn't include at the time because the article was already long enough. His GP hadn't just flagged his cholesterol. She'd also noted his HbA1c was sitting at 43 mmol/mol. Not diabetic. But not normal either. Pre-diabetic range.
He went quiet on the phone for a moment. Then he said: "But I feel fine."
And that, in five words, is the entire problem with blood sugar dysregulation. You feel fine. You feel completely, utterly normal. Right up until you don't. By the time symptoms appear (the thirst, the frequent urination, the fatigue, the blurred vision), the underlying process has typically been building for years.
Pre-diabetes is one of the most underappreciated conditions in Australian healthcare. Clinically, the RACGP recommends active intervention. But psychologically it barely registers because there's nothing to feel. Your body is losing its ability to regulate blood sugar efficiently, and you have no idea.
Over 1.3 million Australians are living with diagnosed diabetes. The pre-diabetes population is substantially larger, and many of those people don't know. Recent ABS data from the National Health Measures Survey found that 0.9% of tested adults had previously undiagnosed diabetes picked up by HbA1c screening. That's people walking around with diabetes they didn't know about, found by a test they may not have had if someone hadn't thought to order it.
HbA1c is the test that catches the drift. Not a single morning's fasting glucose. Not a random finger prick. A three-month average that tells you what your blood sugar has actually been doing while you weren't paying attention.
This article explains what HbA1c measures, what the numbers mean, who should be checking, and what to do if you're in that unsettling grey zone between normal and diabetic.
A note before we get into it
General information only. I'm not a doctor. Diabetes management is a clinical decision that requires ongoing care from your GP or endocrinologist.
If you have diagnosed diabetes, are on blood sugar-lowering medication, or are pregnant, work with your clinician for interpretation and management. This article is focused primarily on screening and early detection in people who haven't been diagnosed.
What HbA1c actually measures, and why it's different from a glucose test
HbA1c stands for glycated haemoglobin. Here's what that means in plain language.
Haemoglobin is the protein inside your red blood cells that carries oxygen. When glucose is present in your blood (which it always is, that's normal), some of it attaches to haemoglobin. The more glucose in your blood over time, the more haemoglobin gets "glycated." Sugar-coated, essentially.
Since red blood cells live for roughly 120 days, the percentage of haemoglobin that's glycated reflects your average blood sugar exposure over the preceding 2–3 months. That's the key advantage of HbA1c: it's not a single moment. It's a trend.
Fasting glucose tells you what your blood sugar is doing right now, after an overnight fast. It's useful, but it's a photograph. HbA1c is a time-lapse. Your fasting glucose could look acceptable on the morning of your test while your average exposure over weeks has been quietly elevated. HbA1c catches that pattern.
This is why HbA1c has become the preferred test for both diagnosing diabetes and monitoring long-term blood sugar control. It's harder to game. It doesn't depend on what you ate yesterday. It tells you what's actually been happening.
Why HbA1c matters more than most people realise
Type 2 diabetes doesn't start on the day it's diagnosed. It develops over years, typically through a progression that looks something like this:
Normal blood sugar regulation → insulin resistance begins (your cells start responding less efficiently to insulin) → your pancreas compensates by producing more insulin → blood sugar stays normal but insulin is elevated → eventually the pancreas can't keep up → blood sugar starts rising → pre-diabetes → type 2 diabetes.
That middle section, where your body is compensating and your glucose still looks fine, can last for years. During that time, the only way to detect the drift is through a test sensitive enough to pick up the trend. HbA1c is that test.
The drift matters. Pre-diabetes isn't just a label. Research shows that roughly 5–10% of people with pre-diabetes progress to type 2 diabetes each year. Without intervention, many will develop diabetes within 5–10 years.
Here's the critical part: lifestyle intervention during the pre-diabetes window can reduce progression risk by up to 58%, based on large, well-designed intervention trials (including the Diabetes Prevention Program). That's a massive reduction, achieved through diet, exercise, and modest weight loss.
Early detection isn't just academic. It's the difference between catching the problem when it's most treatable and catching it after the damage has accumulated.
The numbers: what's normal, what's pre-diabetes, what's diabetes
HbA1c in Australia is reported in two units: mmol/mol (the IFCC standard, used by Australian labs) and percentage (the older DCCT/NGSP standard, still widely referenced internationally). Both measure the same thing.
| Category | HbA1c (mmol/mol) | HbA1c (%) |
|---|---|---|
| Normal | Below 42 | Below 6.0% |
| Pre-diabetes | 42–47 | 6.0–6.4% |
| Diabetes | 48 or above | 6.5% or above |
Important caveats
These thresholds are diagnostic guidelines, not rigid cutoffs. An HbA1c of 41 mmol/mol is classified as "normal" and 42 as "pre-diabetes," but the biological difference between those two numbers is negligible. Risk exists on a continuum. The closer you are to the thresholds, the more important monitoring and lifestyle attention become.
Certain conditions can affect HbA1c accuracy. Anything that changes red blood cell lifespan (iron deficiency anaemia, haemolytic anaemia, thalassaemia, recent blood loss or transfusion, chronic kidney disease) can shift HbA1c independently of actual blood sugar. If you have any of these conditions, let your clinician know so they can interpret the result appropriately.
My dad's 43 mmol/mol is barely over the line. His GP was clear: it's not a crisis. But it's a signal. A signal worth paying attention to.
Fasting glucose vs HbA1c: which is better?
The honest answer is they're complementary, not competing.
Fasting glucose is cheap, fast, and widely available. It tells you how your body manages blood sugar after an overnight fast. A single normal reading is reassuring, but it can miss problems that only show up after meals, during stress, or over time. It's also more variable. Your result can shift based on recent meals, exercise, sleep, stress, and illness.
HbA1c is more stable, doesn't require fasting, and provides a longer-term view. It's better at detecting the slow, gradual drift that characterises early type 2 diabetes. But it's slightly more expensive and can be affected by conditions that alter red blood cell turnover.
For screening purposes, either test is acceptable according to Australian guidelines. The RACGP recommends using either fasting glucose or HbA1c for diabetes screening in at-risk individuals.
If I had to choose one (and I realise this is a personal view, not a clinical recommendation), I'd pick HbA1c. Mainly because it captures the trend rather than a single moment, and because it doesn't require fasting, which removes a barrier to actually doing the test.
But if you're doing a fasting blood draw anyway for lipids or iron studies, adding fasting glucose alongside HbA1c gives you both perspectives at no extra inconvenience. That's what I do when I test through Bloody Good. Both markers, same blood draw, more information.
Who should be testing
Everyone over 40 with any risk factors. The risk factor list is broader than most people expect:
Overweight or obesity, particularly abdominal adiposity. Family history of type 2 diabetes (first-degree relative). Physical inactivity. History of gestational diabetes. Polycystic ovary syndrome (PCOS), covered in our PCOS blood test guide. Aboriginal or Torres Strait Islander heritage. South-East Asian, South Asian, Middle Eastern, North African, or Pacific Islander background. History of cardiovascular disease. Currently taking medications that affect blood sugar (corticosteroids, antipsychotics, some others). Previous impaired fasting glucose or impaired glucose tolerance.
Aboriginal and Torres Strait Islander peoples from age 18. Diabetes prevalence is significantly higher in this population, and earlier screening is recommended.
People with pre-diabetes. Should be retested annually.
Anyone with symptoms suggestive of diabetes. Unexplained thirst, frequent urination, unexplained weight loss, fatigue, blurred vision, slow wound healing. Though by the time these symptoms appear, the condition is usually established.
People who've never been tested and are curious. If you're over 35, lead a sedentary lifestyle, carry extra weight around the middle, and have never had blood sugar checked, this might be one of the most useful tests you can do. It takes five minutes and tells you something that could genuinely change your trajectory.
How to prepare for the test
No fasting required. HbA1c reflects the previous 2–3 months regardless of what you did yesterday. Eat normally.
Combining with other tests? If you're also testing fasting glucose or lipids, you'll need to fast for 8–12 hours for those. Water is fine.
Test in the morning if you're combining with other fasting markers. HbA1c alone can be done any time of day.
Understanding your result
HbA1c result ranges
Below 42 mmol/mol (below 6.0%)
Normal. Blood sugar regulation is working well over the medium term. Retest based on your risk profile: every 3–5 years if low risk, annually if you have risk factors.
42–47 mmol/mol (6.0–6.4%)
Pre-diabetes. Your blood sugar is higher than ideal but below the diabetes threshold. This is the intervention window. Lifestyle changes here have the highest return on investment. Your GP should be involved.
48 mmol/mol (6.5%) or above
Consistent with diabetes. A single result above 48 should be confirmed with a repeat test (or corroborated with fasting glucose or an oral glucose tolerance test) before a formal diagnosis is made. If confirmed, your GP will discuss management options.
For people already diagnosed with diabetes
The RACGP recommends a general target of 53 mmol/mol (7.0%) or below for most people with type 2 diabetes, though individual targets may vary depending on age, duration of diabetes, other health conditions, and risk of hypoglycaemia. Recent ABS data found that only about half of Australians with known diabetes have their HbA1c within this target range, which suggests there's significant room for improvement in diabetes management nationally.
Pre-diabetes: the window most people miss
I keep coming back to this because I think it's genuinely the most important part of the article.
Pre-diabetes affects a large proportion of the Australian adult population. Many people in this range don't know they're in it. It produces no symptoms. It doesn't make you feel sick. Left unaddressed, it progresses to type 2 diabetes in a substantial percentage of cases.
But it's also the most responsive stage. Research consistently shows that lifestyle intervention (moderate weight loss of 5–7% of body weight, increased physical activity of 150+ minutes per week, and dietary improvements) can reduce the risk of progressing from pre-diabetes to diabetes by around 58%. That number comes from large, well-designed intervention trials and it's one of the most impressive risk reductions in preventive medicine.
Medication (typically metformin) is sometimes considered alongside lifestyle changes, particularly for people with multiple risk factors or progressive glucose impairment. But lifestyle is the foundation.
My dad, incidentally, took his result of 43 mmol/mol seriously. He was already active and eating well, but his GP pointed out that he'd gained about 6 kilograms over the past three years. Gradually, almost invisibly. His waist circumference had crept up. She suggested focusing on that modest weight gain alongside continuing his existing habits. Six months later, his HbA1c was 40 mmol/mol. Back in the normal range.
That's not a guarantee it'll work the same for everyone. But it illustrates the point: pre-diabetes is a signal, not a sentence. The earlier you catch it, the more room you have to respond.
What actually moves HbA1c
If your HbA1c is elevated, the interventions with the best evidence are:
Weight management. Even modest weight loss of 5% of body weight has a meaningful effect on insulin sensitivity and blood sugar regulation. You don't need to reach an "ideal" weight. You need to shift the trajectory.
Physical activity. Both aerobic exercise and resistance training improve insulin sensitivity independently. The combination is more effective than either alone. 150 minutes per week of moderate-intensity activity is the standard recommendation.
Dietary quality. Reducing refined carbohydrates and added sugars. Increasing fibre (vegetables, legumes, whole grains). Choosing foods with a lower glycaemic impact. The Mediterranean dietary pattern has strong evidence here. It's not about extreme restriction. It's about consistently better choices.
Sleep. Poor sleep quality and insufficient sleep are independently associated with impaired glucose regulation. This gets overlooked constantly. If you're sleeping less than 6 hours most nights or your sleep quality is poor, addressing that may have as much metabolic impact as dietary changes.
Stress management. Chronic stress elevates cortisol, which directly raises blood sugar. This isn't a soft recommendation. It's physiological. If you're chronically stressed and your HbA1c is elevated, the stress is a contributing factor worth addressing.
Alcohol reduction. Alcohol interferes with blood sugar regulation in complex ways, causing both highs and lows depending on context. Reducing or eliminating alcohol, particularly if consumption is regular, often improves metabolic markers.
The pattern here is familiar. It's essentially the same set of lifestyle foundations that come up for nearly every biomarker in this series. Either reassuring (one set of habits, many benefits) or frustrating (no magic bullet), depending on your perspective.
Tests to consider through Bloody Good
The core blood sugar test
HbA1c (Glycated Haemoglobin) Blood Test — your 3-month blood sugar average. No fasting required.
Complementary blood sugar markers
Fasting Glucose Blood Test. Point-in-time snapshot. Best when combined with HbA1c. Requires fasting.
Fasting Insulin Blood Test. Detects elevated insulin even when glucose is still normal. Useful for identifying early insulin resistance.
Metabolic context markers
Cholesterol (Lipid Studies inc. HDL). Dyslipidaemia and blood sugar dysregulation frequently travel together. The triglyceride-high / HDL-low pattern is a metabolic red flag.
Liver Function Test (LFT). Non-alcoholic fatty liver disease (NAFLD) is strongly associated with insulin resistance and pre-diabetes.
High-Sensitivity CRP. Chronic low-grade inflammation is linked to insulin resistance.
Related fatigue markers
Iron Studies (Including Ferritin). Fatigue from iron deficiency can coexist with fatigue from blood sugar dysregulation.
Thyroid Function Test (TFT). Hypothyroidism and metabolic dysfunction overlap significantly.
If you want broad coverage
The Bloody Good Test covers 100 biomarkers including HbA1c, fasting glucose, the full lipid panel, liver and kidney function, thyroid, iron, and more. For a metabolic baseline, this covers all the relevant markers in a single blood draw.
Biomarker info: HbA1c (IFCC)
When to retest
Normal result, low risk. Every 3–5 years, or sooner if risk factors change.
Normal result with risk factors. Annually.
Pre-diabetes range. Every 6–12 months, to track whether interventions are working and whether you're progressing or improving.
Diagnosed diabetes. Your GP or endocrinologist will advise. Typically every 3–6 months, aligned with medication adjustments and management reviews.
After a significant lifestyle change. If you've lost weight, started an exercise programme, changed your diet substantially, or started medication, retest at 3 months. That's the minimum time needed for changes to show up in HbA1c.
After an event that might affect the result. Iron supplementation, blood transfusion, or changes in haematological status. Discuss with your clinician whether HbA1c remains the best marker, or whether fasting glucose should be used alongside it.
Explore more biomarkers
If you want to go deeper into any of the markers covered here, the Bloody Good biomarker directory has detailed pages on what each test measures.
Browse the Bloody Good Biomarker Directory
General information only. This article is not medical advice and is not a substitute for care from a qualified health professional. If you have concerning symptoms or urgent health issues, seek medical attention promptly.