A normal A1C is below 5.7%. This number represents your average blood sugar over roughly the past three months, expressed as a percentage. An A1C between 5.7% and 6.4% falls into the prediabetes range, and 6.5% or higher indicates diabetes. Any result used for diagnosis needs to be confirmed with a second test unless you already have clear symptoms of diabetes.
What the A1C Number Actually Measures
Sugar in your bloodstream naturally attaches to hemoglobin, the protein inside red blood cells that carries oxygen. The more sugar in your blood over time, the more hemoglobin gets coated. Since red blood cells live about 120 days, measuring the percentage of sugar-coated hemoglobin gives a reliable picture of your average blood sugar over the past two to three months.
One important detail: the test isn’t weighted equally across that whole window. Your blood sugar levels from the most recent 30 days contribute more to the result than levels from 90 to 120 days earlier. So if you’ve made significant dietary changes in the last month, your next A1C will partially reflect those efforts, even though the full picture takes about three months to shift.
What Each Range Means
The three diagnostic categories break down like this:
- Below 5.7%: Normal. Your body is managing blood sugar effectively.
- 5.7% to 6.4%: Prediabetes. Your blood sugar is higher than normal but not yet in the diabetes range. This is a window where lifestyle changes can make a real difference.
- 6.5% or above: Diabetes. This level indicates your blood sugar has been consistently elevated enough to warrant treatment.
To put these percentages in more concrete terms, you can convert A1C to an estimated average glucose. An A1C of 5.7% translates to an average blood sugar of roughly 117 mg/dL. At 6.5%, that average climbs to about 140 mg/dL. At 7%, it’s around 154 mg/dL. The formula behind these conversions is straightforward: multiply your A1C by 28.7, then subtract 46.7.
A1C Targets If You Have Diabetes
A “normal” A1C and a “target” A1C are different things. If you’ve been diagnosed with diabetes, the goal typically isn’t to get back below 5.7%. Instead, most adults aim for an A1C under 7%, which corresponds to an average blood sugar of about 154 mg/dL. Pushing too aggressively toward a lower number can increase the risk of dangerous blood sugar drops, especially if you’re on insulin or certain medications.
For children and adolescents with type 1 diabetes, the American Diabetes Association recommends a target under 7% as well. Kids with type 2 diabetes who have a low risk of blood sugar drops may aim for under 6.5%. These targets get adjusted based on individual factors, including whether a child can recognize symptoms of low blood sugar and what technology they have access to for monitoring.
How Targets Change for Older Adults
A1C goals look different for older adults, and the reason is practical: the risks of aggressive blood sugar control can outweigh the benefits. Older adults are more vulnerable to low blood sugar episodes because of irregular eating patterns, declining kidney function, and the medications they may be taking. A severe blood sugar drop can cause falls, confusion, or hospitalization.
Current guidelines from the American Diabetes Association break older adults into three categories. Healthy older adults with few other chronic conditions generally aim for an A1C under 7.0% to 7.5%. Those with multiple chronic illnesses, some cognitive decline, or difficulty with daily activities have a more relaxed target of under 8.0%. For older adults in poor health or with significant cognitive impairment, the focus shifts away from hitting a specific A1C number entirely. The priority becomes avoiding both dangerously low and symptomatically high blood sugar rather than chasing a percentage.
When A1C Results Can Be Misleading
Certain conditions can push your A1C reading higher or lower than your actual blood sugar levels would suggest. Since the test depends on hemoglobin inside red blood cells, anything that changes how long those cells live or how hemoglobin behaves will affect accuracy.
Conditions that shorten the lifespan of red blood cells, like hemolytic anemia or recovery from significant blood loss, cause A1C results to read falsely low. Your red blood cells simply haven’t been around long enough to accumulate sugar at a rate that reflects your real averages. On the other hand, iron deficiency anemia tends to push A1C readings falsely high, which is particularly relevant during late pregnancy, when iron deficiency is common.
People with sickle cell disease or other hemoglobin variants (such as hemoglobin C) need to interpret their A1C results with extra caution. The abnormal hemoglobin, combined with higher red cell turnover and potential transfusion history, makes A1C unreliable as a standalone measure. Chronic kidney disease, especially in people on dialysis, also tends to make A1C underestimate true blood sugar levels. In these situations, alternative tests that measure sugar attached to different proteins in the blood can give a more accurate picture.
How Often to Get Tested
If your A1C is normal, routine screening depends on your risk factors. People over 45 or those with risk factors like obesity, a family history of diabetes, or a sedentary lifestyle typically get screened every three years. If your result comes back in the prediabetes range, your doctor will likely recheck it annually to track whether it’s stable, improving, or progressing toward diabetes.
For people with diabetes, A1C testing usually happens two to four times per year. If your blood sugar is well controlled and stable, twice a year is often sufficient. If your treatment plan has recently changed or your numbers are above target, testing every three months helps gauge whether adjustments are working. Because the test reflects a weighted average that leans toward the most recent month, retesting sooner than every three months won’t capture a full new cycle of data.