Biomarker guide
HbA1c explained: lab ranges vs optimal ranges
HbA1c is one of the most commonly requested blood markers in Australia — and one of the most misunderstood. Here is what it measures and how to read it.
What HbA1c measures
Glucose in your bloodstream naturally attaches to haemoglobin, the protein in red blood cells that carries oxygen. The HbA1c test measures what percentage of your haemoglobin has glucose attached — the more glucose circulating over time, the higher the percentage.
It reflects months, not days
Because red blood cells live for around three months, HbA1c reflects your average blood glucose over that period. A single healthy week will not move it much — and neither will one indulgent weekend.
It is reported as a percentage
Australian laboratories report HbA1c as a percentage of haemoglobin that has glucose attached (mmol/mol is also shown on most reports). Higher percentages mean higher average glucose exposure.
It is one marker, not the whole picture
HbA1c is an average, so it can hide swings between highs and lows. Fasting glucose, fasting insulin and other metabolic markers add context your practitioner may want to see alongside it.
Three ways the same result gets read
A single HbA1c number can be read against three different sets of ranges. Understanding the difference explains why a result can be labelled 'normal' and still be worth a conversation.
Laboratory reference range
The range the pathology lab prints on your result. It describes where most of the tested population falls and is used to flag results that may need medical attention. A result inside this range is reported as 'normal' by the lab.
Guideline thresholds
Cut-offs published by clinical guideline bodies — for example the values used to define diabetes and pre-diabetes categories. These are the thresholds your doctor uses when making diagnostic decisions.
Functional optimal range
A narrower range used in functional and preventive health practice, reflecting values associated with lower long-term metabolic risk in research literature. A result can be 'normal' to the lab yet outside this optimal range — that is where preventive conversations usually start.
If your result is outside your optimal range
A result outside the functional optimal range is not a diagnosis — it is a prompt to look at the everyday factors that influence average glucose. Topics people commonly discuss with their practitioner include:
- Reviewing meal composition and timing, particularly refined carbohydrate intake
- Regular movement after meals and across the week
- Sleep quality and consistency
- Body composition and waist circumference
- Retesting after a period of change to see the trend, not just one reading
Any result outside the laboratory reference range should be discussed with your doctor.
See how HbA1c appears in a Bloodwork Studio report
Our sample report shows how each marker is presented against laboratory, guideline and optimal ranges, with the source of every status kept clear.
Related guides: Optimal vs reference ranges — how Australian blood test results are read
General information only, not medical advice. Always discuss your results with a qualified health practitioner.