What this test measures
Glucose in the bloodstream attaches to haemoglobin inside red blood cells, slowly and irreversibly. The more glucose has been present, the higher the proportion of haemoglobin carrying it. HbA1c measures that proportion.
Because a red blood cell lives for roughly three months, the result behaves like an average of your blood glucose across that window — weighted towards the more recent weeks. This is what makes it useful. A fasting glucose tells you about one morning; HbA1c tells you about a season.
It does not require fasting, is not much affected by a single indulgent meal, and can be drawn at any time of day. Those are real practical advantages, and they are why it has become the default screening test.
What it cannot do is show variability. Two people with an identical HbA1c of 6.0% may have quite different glucose patterns — one steady, the other swinging high after meals and low between them. In South Asians the post-meal rise tends to appear earlier than the fasting rise, which is why a glucose tolerance test is still sometimes needed even when HbA1c looks acceptable.
What your result means
Below 5.7% is normal. Between 5.7% and 6.4% is the prediabetic range. 6.5% or above on two separate occasions is consistent with diabetes.
Those thresholds are boundaries on a continuous scale, not cliffs. A result of 5.6% and a result of 5.8% describe almost the same physiology, and the difference between them is within the test's own variation. What is more informative is where the number sits within the range and which direction it has moved since last time.
A result in the prediabetic range is genuinely worth acting on. Risk to blood vessels and nerves begins below the diabetic threshold, and the interventions that reverse it work considerably better before diabetes is established.
Before accepting any result, check whether anything could be distorting it. Iron deficiency anaemia raises HbA1c independently of glucose, and is very common. Anything that shortens red cell survival — haemolysis, recent blood loss, pregnancy, thalassaemia trait, chronic kidney disease — lowers it. If your HbA1c does not match your fasting glucose or your clinical picture, that mismatch is worth investigating rather than averaging.
What each value means
Reference ranges differ between laboratories. Always read your result against the range printed on your own report.
HbA1c
Reference range
4 – 5.6 %
- What it means
- The proportion of haemoglobin that has glucose attached to it. Because red cells live about three months, it reflects average glucose over that period rather than glucose on the morning of the test.
- Why it matters
- 6.1% sits in the upper half of the prediabetic range (5.7–6.4%), where the chance of progressing to type 2 diabetes over five years is meaningful but the change is still very reversible.
- Next step
- Confirm with a repeat, add a fasting lipid profile and a liver assessment, and begin structured lifestyle change now rather than rechecking in a year.
Interpret in context. One result doesn't tell the whole story.
Estimated average glucose
70 – 114 mg/dL
A direct arithmetic conversion of HbA1c into familiar glucose units. It adds no new information — it is the same number in a different language, printed because it is easier to picture.
Fasting plasma glucose
70 – 99 mg/dL
A single snapshot after eight hours without food. Often reported alongside HbA1c because the two can disagree, and the disagreement is itself informative.
This is general education and cannot account for your history, your examination or your reports. If you need advice specific to your health, we’re always happy to see you in consultation.
What to do next
Confirm before concluding. A single result in the prediabetic or diabetic range should be repeated, and ideally paired with a fasting glucose so the two can be read against each other.
Look at what travels with it. Insulin resistance rarely affects glucose alone, so a first assessment usually includes a fasting lipid profile, blood pressure, waist measurement and a look at the liver. Finding fatty liver at the same time is common and does not change the plan — it strengthens the case for it.
Start the changes now rather than at the next review. Sustained weight reduction where relevant, resistance training twice a week, less refined carbohydrate and added sugar, and adequate sleep are the levers with the strongest evidence behind them, and they work best at this stage.
Repeat at three to six months. Sooner than that and you are measuring the test's own variation rather than your progress.
This information is educational and not a diagnosis.
Alitheau Learning Sessions
Understanding Blood Reports
- Why reference ranges differ between laboratories, and what that means for you
- How to read a liver function test, and why the pattern beats the worst number
- What HbA1c actually measures, and the common things that distort it
One result rarely tells the whole story
Have this read alongside everything else.
Conditions this result comes up in
Questions people ask
Below 5.7% is generally reported as normal, 5.7–6.4% as prediabetes, and 6.5% or above as consistent with diabetes on two occasions. Read these against the range printed on your own report.
No. That is one of its practical advantages. Fasting is only requested when glucose or a lipid profile is being drawn at the same time.
It can be misleading. Iron deficiency anaemia tends to raise it; haemolysis, recent blood loss, pregnancy, chronic kidney disease and thalassaemia trait tend to lower it. All of these are common enough in India that a result which does not fit the clinical picture should be checked another way.
Meaningfully over about three months, because that is the lifespan of a red cell. Repeating it after four weeks measures mostly noise.