A normal A1c level is below 5.7%. This number represents the percentage of your red blood cells that have glucose attached to them, averaged over roughly three months. An A1c between 5.7% and 6.4% falls into the prediabetes range, and 6.5% or higher meets the threshold for diabetes.
What the A1c Test Measures
Glucose in your bloodstream naturally sticks to hemoglobin, the protein inside red blood cells that carries oxygen. The more glucose circulating in your blood over time, the more hemoglobin gets coated. Since red blood cells live about three months before your body replaces them, an A1c test captures a rolling average of your blood sugar over that entire window rather than a single snapshot.
This makes A1c fundamentally different from a fingerstick glucose reading or a fasting blood sugar test. Those measure what’s happening right now. A1c tells you what’s been happening for the past 8 to 12 weeks, which is why it’s the primary tool for diagnosing diabetes and tracking how well blood sugar is being managed over time.
The Three A1c Ranges
The American Diabetes Association defines three categories based on A1c percentage:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher
An A1c of 5.0%, for example, corresponds to an estimated average blood sugar of about 97 mg/dL. At 6.0%, that average climbs to roughly 126 mg/dL. At 7.0%, you’re looking at an average around 154 mg/dL. These conversions help translate a percentage into something more concrete if you’re used to seeing blood sugar numbers on a glucose meter.
A single A1c result at or above 6.5% doesn’t always lock in a diabetes diagnosis on its own. In the absence of clear symptoms like excessive thirst, frequent urination, or unexplained weight loss, a confirmatory test is typically needed. That could be a repeat A1c or a different type of blood sugar test.
What Prediabetes Means in Practice
Landing in the 5.7% to 6.4% range doesn’t mean you have diabetes, but it does mean your body is processing sugar less efficiently than it should. About 38% of U.S. adults fall into this category. The good news is that prediabetes is the stage where lifestyle changes have the most impact. Losing 5% to 7% of body weight and getting roughly 150 minutes of moderate physical activity per week have been shown to cut the risk of progressing to type 2 diabetes by more than half.
If your A1c sits at the lower end of prediabetes, say 5.7% or 5.8%, you have more runway. At 6.3% or 6.4%, you’re close to the diabetes threshold, and your doctor will likely want to recheck sooner and discuss more targeted changes.
A1c Targets for People With Diabetes
Once someone has diabetes, the goal shifts from diagnosis to management. For most nonpregnant adults, the general target is an A1c below 7%. But this isn’t one-size-fits-all. Older adults or people with other serious health conditions may have a higher target, sometimes 7.5% to 8.5%, because aggressively lowering blood sugar can increase the risk of dangerous drops (hypoglycemia) that outweigh the benefits of tighter control.
Younger, otherwise healthy people with a recent diabetes diagnosis often aim for something closer to 6.5%, since keeping blood sugar well controlled early on reduces the risk of complications affecting the eyes, kidneys, and nerves over decades.
Factors That Can Skew Your Results
A1c is reliable for most people, but certain conditions can push results artificially high or low. Anything that changes how long your red blood cells survive or alters the hemoglobin inside them can throw off the reading.
Conditions that may cause inaccurate A1c results include:
- Severe anemia: fewer or shorter-lived red blood cells change how much glucose accumulates on them
- Kidney failure or liver disease: both can alter red blood cell turnover
- Blood loss or transfusions: replacing blood dilutes or disrupts the normal aging of red blood cells
- Pregnancy: especially early or late pregnancy, when blood volume and red blood cell production shift significantly
- Certain medications: including opioids and some HIV treatments
If any of these apply to you, your doctor may rely more on other blood sugar tests, like fasting glucose or an oral glucose tolerance test, to get an accurate picture.
How Ancestry Can Affect A1c Accuracy
Hemoglobin comes in different forms depending on the genes you inherit. The most common type is hemoglobin A, which is what standard A1c tests are designed to measure. But millions of people carry hemoglobin variants, including hemoglobin S (associated with sickle cell trait), hemoglobin C, and hemoglobin E. These variants are more common in people with African, South Asian, Southeast Asian, and Mediterranean ancestry.
Carrying a hemoglobin variant doesn’t change your risk of diabetes, but it can make A1c results read falsely high or falsely low depending on the specific variant and the lab method used. This matters because an inaccurate A1c could lead to a missed diagnosis or unnecessary treatment. If you know you carry a hemoglobin variant, or if your A1c results seem inconsistent with your daily glucose readings, your doctor can order a test method that accounts for the variant or use alternative blood sugar tests instead.
How Often to Get Tested
If your A1c is normal and you have no risk factors for diabetes, periodic screening is generally recommended starting at age 35. For people with prediabetes, retesting every one to two years helps track whether blood sugar is holding steady or creeping upward. People with diagnosed diabetes typically get A1c tested two to four times a year, depending on whether their levels are stable or their treatment has recently changed.
The test itself is simple: a standard blood draw, no fasting required. Results are usually available within a day or two. Some clinics use a rapid point-of-care device that gives results in minutes, though lab-based tests are considered more precise for diagnosis.