Blood test
HbA1c Test (Blood Sugar)
The HbA1c is a blood test that shows your average blood sugar over the past two to three months. It is used to diagnose and monitor diabetes.
Quick answer
HbA1c Test (Blood Sugar): what it is and what the results mean
HbA1c measures how much sugar has attached to the haemoglobin in red blood cells, reflecting average blood glucose over recent months rather than at a single moment.
- Why it is done: It is used to diagnose type 2 diabetes and prediabetes, and to monitor how well diabetes is being controlled over time.
- Understanding results: Higher HbA1c means higher average blood sugar.
What it is
HbA1c measures how much sugar has attached to the haemoglobin in red blood cells, reflecting average blood glucose over recent months rather than at a single moment.
Why it is done
It is used to diagnose type 2 diabetes and prediabetes, and to monitor how well diabetes is being controlled over time.
What to expect
It is a routine blood test from the arm and, unlike some sugar tests, usually does not require fasting.
Understanding the results
Higher HbA1c means higher average blood sugar. Specific thresholds define prediabetes and diabetes, and for people with diabetes a target is set with their clinician. Results guide diagnosis and treatment.
Good to know
Risks and limitations
Risks are those of a routine blood test. Certain conditions affecting red blood cells can make HbA1c less reliable, so other tests are sometimes used.
Education and reference only. This explains the test in general terms and is not medical advice. Always follow the specific instructions from the team arranging your test, and discuss your results with your clinician.
Answers
HbA1c Test (Blood Sugar): frequently asked questions
What does HbA1c measure?
It measures your average blood sugar over the past two to three months, which is why it is used to diagnose and monitor diabetes.
Do I need to fast for an HbA1c test?
Usually no. Unlike some glucose tests, HbA1c reflects long-term average sugar, so fasting is generally not required.
Related tests
Other blood test investigations
Sources
Where this is drawn from
- NHS — Tests and treatments
- NICE — diagnostic guidance
- Royal College of Radiologists / relevant professional body
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