A normal A1C is below 5.7%. This means that, on average, about 5.7% or less of the hemoglobin in your red blood cells has glucose attached to it. An A1C between 5.7% and 6.4% falls into the prediabetes range, and 6.5% or higher on two separate tests indicates diabetes.
What the A1C Test Actually Measures
Glucose in your bloodstream naturally sticks to hemoglobin, the oxygen-carrying protein inside red blood cells. The more glucose in your blood over time, the more hemoglobin gets coated. Because red blood cells live about three months, an A1C test captures your average blood sugar over that entire window rather than a single snapshot. That’s what makes it different from a finger-stick glucose reading, which only tells you what’s happening right now.
An A1C of 5.7% corresponds to an estimated average blood sugar of roughly 117 mg/dL. At 6.5%, the diagnostic threshold for diabetes, your average sits around 140 mg/dL. A 7% A1C translates to an estimated average of 154 mg/dL. These conversions help connect the percentage to something more concrete if you’re used to checking blood sugar with a meter.
The Three A1C Categories
- Normal: Below 5.7%. Blood sugar regulation is working well.
- Prediabetes: 5.7% to 6.4%. Blood sugar is higher than it should be but not yet in the diabetes range. This is the stage where lifestyle changes (more movement, dietary shifts, modest weight loss) can often prevent progression.
- Diabetes: 6.5% or higher on two separate tests. At this level, sustained high blood sugar begins to raise the risk of damage to blood vessels, nerves, kidneys, and eyes.
These cutoffs come from the American Diabetes Association and are used across most clinical settings in the U.S. The ADA places A1C at the top of its testing hierarchy when diagnosing both diabetes and prediabetes, reflecting how widely it’s used in everyday practice.
How “Normal” Shifts With Age
For most adults, the goal is to stay below 5.7% if you don’t have diabetes, or below 7% if you do. But for older adults, the picture gets more nuanced. The ADA’s 2024 guidelines break it down by overall health status rather than age alone.
Older adults who are otherwise healthy, with stable health and sharp cognitive function, are generally encouraged to aim for an A1C below 7.0% to 7.5%. Those managing multiple chronic conditions or dealing with mild to moderate cognitive decline have a more relaxed target of below 8.0%. For people in poor health or with severe cognitive impairment, guidelines recommend stepping away from A1C targets entirely and focusing instead on avoiding dangerously low or high blood sugar episodes. The reasoning is straightforward: tight blood sugar control carries a risk of hypoglycemia, and for someone who is frail or cognitively impaired, a low blood sugar episode can be more immediately dangerous than a slightly elevated A1C.
A1C Targets During Pregnancy
Pregnancy tightens the targets. Before conception and during the first trimester, the goal for women with preexisting diabetes is an A1C below 7%, ideally as close to 6% as possible without causing low blood sugar. By the second and third trimesters, the target drops to below 6%. These stricter numbers reflect the fact that even moderately elevated blood sugar during pregnancy can affect fetal development.
It’s also worth noting that pregnancy itself can make A1C readings less reliable. Changes in blood volume and red blood cell turnover during early and late pregnancy can shift results in either direction, which is why many providers rely more heavily on direct blood sugar monitoring during this time.
When A1C Results Can Be Misleading
The test assumes your red blood cells have a normal lifespan and that your hemoglobin is structurally typical. Several conditions can throw off results. Severe anemia, kidney failure, and liver disease can all skew A1C readings higher or lower than your actual average blood sugar. Blood disorders like sickle cell anemia or thalassemia alter hemoglobin structure, which directly interferes with how the test works. Certain medications, including opioids and some HIV treatments, can also affect accuracy. Recent blood loss or transfusions reset the age of your red blood cells, making the three-month average unreliable.
If any of these apply to you, your provider may use alternative tests like fructosamine (which measures a shorter, two-to-three-week average) or rely on direct glucose monitoring instead. A falsely low A1C can be particularly risky because it may mask blood sugar levels that actually need attention.
How Often to Get Tested
If you’ve never had an abnormal glucose result, the U.S. Preventive Services Task Force suggests screening every three years as a reasonable interval. The USPSTF recommends screening for prediabetes and type 2 diabetes in adults aged 35 to 70 who are overweight or obese. If your result comes back in the prediabetes range, your provider will likely want to recheck more frequently, typically every one to two years, to track whether your levels are stable, improving, or progressing. People already diagnosed with diabetes usually get tested two to four times per year depending on how well-controlled their blood sugar is.
Because the A1C reflects a rolling three-month average, testing more often than every three months won’t give you meaningfully new information. If you’ve recently made significant changes to your diet or activity level, you’ll need at least two to three months before the A1C will reflect those efforts.