The A1C test is a blood test that measures a person’s average blood glucose levels over the past 3 months. Blood glucose is another name for blood sugar.
Doctors use the A1C test to check for:
This test also helps doctors monitor blood glucose levels in people with diagnosed diabetes.
Keeping A1C levels within the normal or target range lowers the risk of developing diabetes or its complications. Read on to learn what A1C test results mean.
The A1C chart below can help a person convert and understand their A1C test results. The doctor can provide more context and describe ways to keep blood glucose levels in a safe range.
The A1C test is also known as the:
The A1C test measures the percentage of red blood cells that have glucose-coated hemoglobin. This measurement gives doctors an idea of the person’s average blood glucose levels over the past 2–3 months.
Hemoglobin is an iron-rich protein in red blood cells. It helps carry oxygen from the lungs to other tissues.
When glucose enters the blood, it binds to hemoglobin. The more glucose in a person’s bloodstream, the more hemoglobin is bound to glucose.
Undergoing the A1C test is straightforward: A healthcare professional takes a blood sample and sends it to a laboratory for testing.
A doctor may order this test to:
If a person takes insulin to manage diabetes, their doctor may also ask them to monitor their blood glucose levels at home with a blood glucose meter or continuous glucose monitor.

In this case, the person still needs to undergo regular A1C testing.
Traditionally, A1C levels are reported as a percentage. Alternately, they may be reported as estimated average glucose (eAG), in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L).
Blood glucose meters and continuous glucose monitors also give eAG readings, some from at least 12 days of data.
The A1C test gives a more accurate long-term average. It takes into account fluctuations throughout the day, such as overnight and after meals.
A normal A1C level is below 5.7%. Normal eAG is below 117 mg/dL or 6.5 mmol/L.
If someone’s A1C levels are higher than normal, they may have diabetes or prediabetes. Their doctor might order a repeat test to confirm this.
A doctor will set a person’s target A1C level based on many factors. The right target varies from person to person.
For someone with diabetes, the target A1C level may depend on:
In general, a doctor might recommend aiming for A1C levels under 6.5% if a person:
A doctor might recommend A1C targets of 7.0–8.5% if a person:
A person should work with their doctor to reassess and adjust their A1C targets over time. The condition and treatment goals may change.
To screen for diabetes, a doctor may order an A1C test for someone older than 45. They may also do this for younger people who have other risk factors.
After diagnosing diabetes, a doctor determines how often to test A1C levels.
If a person is meeting their treatment goals, they may need an A1C test twice a year. When managing blood glucose levels is challenging, a person tends to need this test more frequently.
A person should make an appointment with their doctor if they:
Symptoms of high blood glucose levels include:
Symptoms of low blood glucose levels include:
Anyone who develops any of the symptoms above or notices other changes in their health should let their doctor know.
A doctor orders an A1C test to check whether someone has prediabetes or type 1 or 2 diabetes. Doctors also use this test to monitor blood glucose levels in people with diabetes to see how well their treatment plan is working.
A1C test results are usually a percentage, but they may come as an eAG measurement. Target A1C levels vary from person to person, depending on age, overall health, and other factors.
Having high A1C levels may indicate that the person has diabetes or a high risk of related complications. In this case, the doctor will work with the person to adjust the approach to treatment.
Last medically reviewed on April 12, 2021
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