HbA1c, or glycated haemoglobin, measures the share of haemoglobin in the blood that has glucose attached. It is ordered to help assess longer-term glucose exposure and to follow changes over time. It is not a diagnosis on its own, and the reference range printed on your report is the one that applies.
Because the result integrates weeks of glucose, it answers a different question from a fasting or post-meal glucose test. It also has limits that are easy to miss when a report shows a single number.
What the test measures
Haemoglobin is the oxygen-carrying protein inside red blood cells. Glucose can attach to it, and the share of haemoglobin that carries glucose is what HbA1c reports. Red blood cells circulate for weeks, so the result reflects average glucose exposure over the preceding weeks to months rather than the glucose level at the moment of the draw.
Labs report HbA1c on one of two scales. The NGSP scale is a percentage, and the IFCC scale is mmol/mol. They describe the same measurement in different units. Some reports also print an estimated average glucose derived from the HbA1c value.
Why it may be ordered
- As part of a diabetes panel or an annual health checkup.
- To follow glucose over time when a series of single glucose results is not enough.
- Alongside fasting or post-meal glucose, so the clinician can see both a moment and an average.
- When a clinician wants a result that is less dependent on the timing of the sample than a single glucose test.
It is also ordered in situations where glucose has been measured and the clinician wants a longer view. It is not a universal screening test, and it is not a substitute for a clinical assessment.
The unit on your report
| What you may see | What it means |
|---|---|
| HbA1c, A1c, glycated haemoglobin | The test name. Labs use different abbreviations for the same measurement. |
| % | The NGSP or DCCT scale, common on reports in India and the United States. |
| mmol/mol | The IFCC scale, common on reports in the United Kingdom and parts of Europe. |
| eAG | Estimated average glucose, a value some labs derive from the HbA1c result. |
| A1c, HbA1c (IFCC) | Some reports print both scales side by side. They should describe the same result. |
Why this page does not print a range
A reference range belongs to the laboratory, the method, and the population it was built from. Two labs can report the same HbA1c with different ranges, and the range can also depend on the assay and on the scale the lab uses. A number copied from a website is not your range.
The range printed on the report that produced your value is the one that applies. Doctano keeps that printed range with the result and does not replace it with a general range. If a report shows both percentage and mmol/mol, read the range that matches the unit you are reading.
What a high value can mean
A higher HbA1c means a larger share of haemoglobin has glucose attached, which points to higher average glucose exposure over the preceding weeks to months. Persistently high values are used in the assessment of glucose disorders, and a clinician may read the result alongside fasting glucose, post-meal glucose, and the person's history.
The result is not specific to glucose. Conditions that change how long red blood cells survive, or that change the haemoglobin itself, can move HbA1c in either direction. Examples include some forms of anaemia, recent blood loss or transfusion, pregnancy, and some haemoglobin variants, depending on the assay. That is one reason a high result needs a clinician's reading rather than a conclusion from the number alone.
What a low value can mean
A lower HbA1c means a smaller share of glycated haemoglobin. It can reflect lower average glucose, but it can also reflect a shorter red blood cell lifespan or a change in haemoglobin that affects the assay. Some anaemias, recent blood loss, and pregnancy are examples of conditions that can lower the result without meaning that glucose is low.
A low HbA1c is therefore not automatically a better result. The clinician reads it with the blood count, the glucose results, and the rest of the report.
What can move the value
- Red blood cell lifespan. Anaemia, haemolysis, recent transfusion, or blood loss can change the result.
- Pregnancy. Physiological changes in pregnancy can affect red cell turnover and glucose.
- Haemoglobin variants. Some variants interfere with some assays and not others.
- Assay and calibration. Different labs and methods can produce small differences on the same sample.
- Changes in glucose over time. The result is designed to reflect that average, which is why it moves slowly.
- Medicines that affect glucose. A clinician can say whether a medicine is relevant to a particular result.
What to compare it with
Read HbA1c with the glucose tests on the same report: fasting glucose, post-prandial glucose, and fasting insulin where available. A blood count can help when anaemia is a possibility, because haemoglobin and red cell indices give context for the HbA1c result. The most useful comparison is the previous HbA1c from the same lab on the same scale.
How to see the trend
Doctano reads the HbA1c value, its unit, and the reference range printed on the report. It keeps the range with the result, normalizes the marker name across labs, and places the value on the profile's timeline. Each point still opens the report it came from, so the original page can be checked.
When two reports use different scales, Doctano normalizes units for the timeline. Verify the value and the unit against the original report before treating a change as real, especially when the two results came from different labs.
What this page is not
This page explains the test in general. It does not interpret your result, diagnose a condition, or recommend treatment. It is not medical advice. Verify the value and the unit against the original report, and discuss the result with a qualified professional.