In this article 8 sections
A blood sugar reading tells you what is happening at the time it is measured. HbA1c gives a longer view: it is a blood test that reflects your average blood sugar over approximately the past two to three months. Your report may also call it A1c, glycated haemoglobin or haemoglobin A1c.
What does the test measure
Haemoglobin is a protein in red blood cells that carries oxygen around the body. Glucose attaches to it as blood circulates. The HbA1c test measures the percentage of haemoglobin with glucose attached; generally, a higher percentage means blood sugar has been higher over time.
Because red blood cells remain in circulation for several months, HbA1c reflects a longer period than a single glucose reading. It is useful for understanding the overall pattern, although it cannot show every rise or fall in blood sugar during the day.
Why might your doctor request it
HbA1c can help identify prediabetes or type 2 diabetes. If you already have diabetes, it can also help your healthcare team monitor your condition and assess how your treatment plan is working. Your symptoms, medical history and other blood tests remain part of that assessment.
Understanding the numbers on your report
When HbA1c is used to assess for prediabetes or type 2 diabetes, the commonly used ranges are below 5.7% for the normal range, 5.7% to 6.4% for prediabetes, and 6.5% or above for diabetes. These are diagnostic ranges, rather than a personal treatment target for everyone who already has diabetes.
A result in the diabetes range may need confirmation with a repeat HbA1c or another blood test, particularly if you have no clear symptoms. Your doctor will interpret it alongside the rest of your health information rather than treating the number as a complete diagnosis on its own.
Some reports also show estimated average glucose, or eAG. This translates the HbA1c result into glucose units such as mg/dL. It is an estimate of the longer-term average, so it will not necessarily match a fasting or after-meal reading taken on a particular day.
Is your treatment target the same as the diagnostic range
Once diabetes has been diagnosed, the aim is to reach an HbA1c target that is appropriate and safe for you. For many adults with diabetes, a target below 7% is commonly used, but your healthcare team may recommend something different based on your health and treatment needs.
Age, other health conditions and the risk of low blood sugar can influence that decision. A lower number is not automatically better if reaching it causes repeated low-glucose episodes. Ask your doctor what your own target is and why it suits your circumstances.
How is HbA1c different from home glucose checks
A finger-prick glucose test shows your blood sugar at a particular moment. HbA1c summarises a much longer period. Both can be useful, but they answer different questions: daily readings show immediate changes, while HbA1c helps your healthcare team review the overall pattern.
An average can hide periods of high and low blood sugar. HbA1c therefore does not replace home monitoring when your healthcare team has recommended it.
Do you need to fast and how often is it checked
You do not usually need to fast for an HbA1c test alone. However, if other blood tests are being taken at the same appointment, they may require fasting. Check the instructions for the complete set of tests rather than assuming that every test has the same preparation.
People living with diabetes commonly have HbA1c checked at least twice a year. Your doctor may request it more often when treatment changes or your results are outside the agreed target. The right interval depends on your care plan.
Can other conditions affect the result
HbA1c can be less reliable when a condition changes red blood cells or haemoglobin. Anaemia, certain blood disorders, kidney failure, liver disease, recent blood loss or a blood transfusion can affect the result. Tell your doctor if any of these apply, particularly when HbA1c does not seem to match your glucose readings.
Pregnancy can also affect interpretation, and HbA1c is not the test used to diagnose gestational diabetes. Your doctor may recommend other tests when HbA1c is unsuitable or needs further explanation.
What should you do after receiving your result
If your HbA1c is above your agreed target, arrange a review with your healthcare team. The discussion may include your medicines, eating pattern, activity and any recent illness or changes in your routine. There may be several reasons for a change, so focus on understanding it and agreeing on practical next steps.
Keep the dated report alongside earlier results and note any treatment changes between tests. Looking at the trend can make your next appointment more useful. Ask what the result means for you, what your target should be and when the test should be repeated.