Blood sugar and diabetes
HbA1c blood test: what a high or low result means
What an HbA1c (A1c) blood test measures, what a high result can mean for diabetes, and what to ask your doctor.
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Explain my results → Available on web, iOS & Android.What is HbA1c?
HbA1c, called A1c in the US, measures how much sugar is attached to the haemoglobin in your red blood cells. Because red cells live for about three to four months, HbA1c reflects your average blood sugar over roughly the previous two to three months, rather than at the moment the blood was taken. It is used to diagnose type 2 diabetes and prediabetes, and to monitor diabetes control. You do not need to fast for it.
Why is this test done?
- To check for type 2 diabetes or prediabetes
- To monitor how well diabetes is controlled, often every three to six months
- As part of a health check, especially if you are at higher risk of diabetes
- To guide changes to diabetes treatment
What does a high HbA1c mean?
A high HbA1c means your blood sugar has been higher than usual over recent months. Depending on the level, it can point to prediabetes or diabetes, or show that existing diabetes needs better control.
Possible reasons include:
- Type 2 or type 1 diabetes
- Prediabetes
- Diabetes treatment that needs adjusting
- Some conditions that make HbA1c read falsely high, such as iron deficiency
What does a low HbA1c mean?
A low HbA1c is uncommon. In people treated for diabetes, a low result may mean blood sugar is sometimes running too low.
Possible reasons include:
- Diabetes medicines that lower blood sugar a lot, in people treated for diabetes
- Conditions that shorten the life of red cells, such as recent blood loss or haemolysis, which make HbA1c read falsely low
- Pregnancy
- Some haemoglobin variants, depending on the lab method
Why we don't list a "normal range". Reference ranges differ between laboratories and can depend on your age, sex and whether you are pregnant. The range printed next to your result on your own report is the one that applies to you, so use that, and talk to your doctor about what your result means for you.
What can affect your HbA1c result?
- Conditions affecting red blood cell lifespan: iron deficiency can falsely raise HbA1c, while conditions that break down red cells faster (such as haemolytic anaemia) or recent blood loss can falsely lower it
- Pregnancy
- Kidney disease
- Inherited haemoglobin variants, such as sickle cell trait
- A recent blood transfusion
Make sense of the whole report, not just one line
Results are easier to understand together. Patiently AI explains your report as a whole and writes personalised questions for your next appointment.
Try it with your own results → Paste, upload or photograph your results.Questions to ask your doctor
- Does my HbA1c mean I have prediabetes or diabetes?
- What target should I aim for?
- What changes to diet, activity or medicines would help?
- Could anaemia or anything else be affecting this result?
- When should I be retested?
Frequently asked questions
Do I need to fast before an HbA1c test?
No. HbA1c reflects your average blood sugar over the past two to three months, so eating beforehand does not affect it.
What is the difference between HbA1c and a blood glucose test?
A glucose test measures your blood sugar at one moment, which changes with meals. HbA1c gives an average over months, so it shows the bigger picture.
Can HbA1c be wrong?
It can be misleading in some situations, such as anaemia, recent blood loss, pregnancy, kidney disease and some inherited haemoglobin variants. Your doctor may use glucose tests instead in these cases.
Can Patiently AI explain my HbA1c result?
Yes. Paste your results, or upload a photo, PDF or Word file, and Patiently AI explains them in plain English, sticking to the numbers and ranges on your own report rather than adding its own, and suggests questions to ask your doctor. It is free, needs no account, and removes identifying details on your device first.