DoctorAIThe HbA1c test, also called A1c or glycated hemoglobin, shows your average blood sugar over roughly the past three months. Doctors use it to help diagnose prediabetes and type 2 diabetes and to monitor how well blood sugar is controlled in people who already have diabetes.
What the HbA1c result means
HbA1c is reported as a percentage (common in the US) or in mmol/mol (common in the UK and much of Europe). Both describe the same test. Fasting glucose is shown as a companion test.
| Marker | What it is | Typical adult range | If higher | If lower |
|---|---|---|---|---|
| HbA1c | The share of hemoglobin in red cells that has sugar attached | Normal: under 5.7% (under 39 mmol/mol). Prediabetes range: 5.7 to 6.4% (39 to 46 mmol/mol). Diabetes range: 6.5% or higher (48 mmol/mol or higher) | Average blood sugar has been higher. A diagnosis of diabetes usually needs a repeat test or a second type of test, unless there are clear symptoms with a very high glucose. | Uncommon. It can reflect red cells that live a shorter time, recent blood loss, or, in people taking diabetes medicines, frequent low blood sugar. |
| Estimated average glucose (eAG) | Your A1c converted into the units of a glucose reading | A1c of 5.7% is about 117 mg/dL (6.5 mmol/L). 6.5% is about 140 mg/dL (7.8 mmol/L). 7% is about 154 mg/dL (8.6 mmol/L) | A higher A1c corresponds to a higher average glucose. | A lower A1c corresponds to a lower average glucose. |
| Fasting plasma glucose | Blood sugar after at least 8 hours without food | Normal: under 100 mg/dL (5.6 mmol/L). Prediabetes range: 100 to 125 (5.6 to 6.9). Diabetes range: 126 or higher (7.0 or higher) on repeat testing | May suggest prediabetes or diabetes, particularly if it stays high on repeat tests. | Below 70 mg/dL (3.9 mmol/L) is considered low blood sugar. |
The terms "prediabetes range" and "diabetes range" describe where a number falls. A diagnosis is made by a clinician, usually after confirming the result.
Why ranges and targets differ
The cut-offs in the table are the ones used by the American Diabetes Association. The UK's NHS uses a slightly higher starting point for prediabetes, 42 mmol/mol (6.0%), and the same 48 mmol/mol (6.5%) for diabetes. Your report should print the range your lab uses.
For people who already have diabetes, a common target for many non-pregnant adults is below 7% (53 mmol/mol). Doctors often set a higher or lower personal target depending on age, other health conditions and the risk of low blood sugar.
What can affect your results
Fasting is not needed for an A1c test. The result depends on your red cells, so anything that changes their number or lifespan can make it less reliable:
- Anemia: iron deficiency can raise A1c, while red cells breaking down early, recent heavy blood loss or a recent transfusion can lower it.
- Hemoglobin variants: inherited variants such as sickle cell trait can affect some lab methods. Tell your doctor if you know you have one.
- Pregnancy: red cell turnover changes, so doctors rely more on glucose tests.
- Kidney or liver disease and some medicines: these can also shift the result.
A1c also shows an average, so it can hide large swings between high and low readings within a day.
How the results fit together
- A result in the prediabetes range means blood sugar is higher than usual but below the diabetes range. Lifestyle changes such as regular physical activity and gradual weight loss, when your doctor recommends them, can lower the chance of progressing to type 2 diabetes.
- If A1c and fasting glucose point in different directions, your doctor may repeat one or both, or check for a reason the A1c is unreliable, such as anemia. See CBC results.
- In people with diabetes, home glucose readings or sensor data and the A1c are read together. A mismatch can mean the A1c is affected by one of the factors above.
- Blood sugar problems often come with changes in cholesterol and triglycerides. See lipid panel results.
When to contact a doctor
If your A1c is 5.7% (39 mmol/mol) or above, book a routine appointment to talk about it and whether to repeat the test. Contact your doctor sooner if you notice:
- increased thirst or frequent urination
- unexplained weight loss or constant hunger
- blurred vision or cuts and sores that heal slowly
- tingling or numbness in the hands or feet
Seek urgent care for vomiting with stomach pain, fast breathing, unusual drowsiness or confusion, or for low blood sugar that does not improve after you take sugar. In an emergency, call your local emergency number.
Frequently asked questions
What is a normal HbA1c level?
A normal HbA1c for adults is below 5.7% (39 mmol/mol). A result of 5.7 to 6.4% (39 to 46 mmol/mol) is in the prediabetes range, and 6.5% (48 mmol/mol) or higher is in the diabetes range. Doctors usually confirm a high result with a repeat test before making a diagnosis.
Do I need to fast for an A1c test?
No. HbA1c reflects the past two to three months, so a recent meal does not change it. If your doctor also ordered a fasting glucose or other tests in the same blood draw, you may still be asked to fast for those. Follow the instructions you were given.
Can an A1c result be inaccurate?
Yes. Anemia, recent blood loss or transfusion, pregnancy, kidney or liver disease and inherited hemoglobin variants such as sickle cell trait can make A1c read higher or lower than your true average. Your doctor may then rely on glucose tests or other measures instead.
How often should I have an HbA1c test?
It depends on your situation. For people with diabetes, testing is often done every three to six months, more often when treatment changes or targets are not met. For people with prediabetes or risk factors, many guidelines suggest checking about once a year. Your doctor will advise you.