An A1C between 5.7% and 6.4% is considered prediabetes. Below 5.7% is normal, and 6.5% or higher meets the threshold for type 2 diabetes. This range represents a middle zone where blood sugar is elevated enough to cause concern but hasn’t reached diabetic levels. Roughly 115 million adults in the United States currently fall into this category, and many don’t know it.
What the A1C Test Actually Measures
The A1C test works differently from a finger-stick glucose reading. Instead of capturing your blood sugar at a single moment, it measures the percentage of red blood cells that have glucose stuck to their surface. Since red blood cells live about three months, the result reflects your average blood sugar over that entire period. That’s why you’ll sometimes hear it called a “three-month average.”
This makes the A1C especially useful for spotting patterns. A single fasting glucose reading can be thrown off by what you ate the night before, a bad night of sleep, or stress. The A1C smooths all of that out. It also doesn’t require fasting, so it can be drawn at any time of day.
How the Prediabetes Range Breaks Down
The American Diabetes Association defines the categories like this:
- Normal: A1C below 5.7%
- Prediabetes: A1C of 5.7% to 6.4%
- Diabetes: A1C of 6.5% or higher
Where you fall within that prediabetes range matters. Someone at 5.7% is in a very different position than someone at 6.3%. The closer your number sits to 6.5%, the more aggressively your blood sugar is trending upward, and the more urgently lifestyle changes can help.
A1C isn’t the only way to diagnose prediabetes. Two other tests can also flag it. A fasting plasma glucose between 100 and 125 mg/dL qualifies, as does a two-hour result of 140 to 199 mg/dL on an oral glucose tolerance test. You only need one abnormal result for a prediabetes diagnosis, though sometimes providers will use more than one test to confirm.
When You Should Get Tested
Current guidelines from both the U.S. Preventive Services Task Force and the American Diabetes Association recommend screening starting at age 35, then repeating every three years if results are normal. If you have risk factors like obesity, a family history of diabetes, or a history of gestational diabetes, your provider may start testing earlier or check more frequently.
Because prediabetes rarely causes noticeable symptoms, testing is the only reliable way to catch it. One subtle physical sign worth knowing about: dark, velvety patches of skin in body creases like the neck, armpits, or groin. This condition, called acanthosis nigricans, is a visible marker of insulin resistance and is common in people with prediabetes or obesity. Most people with prediabetes, though, have no outward signs at all.
When A1C Results Can Be Misleading
The A1C test is reliable for most people, but certain conditions can skew results in either direction. Because the test depends on red blood cells, anything that changes how long those cells survive will affect the number.
Iron deficiency anemia can push A1C readings falsely high, making blood sugar look worse than it actually is. This is particularly relevant during late pregnancy, when iron deficiency is common. On the other hand, conditions that shorten the lifespan of red blood cells, like hemolytic anemia or recent significant blood loss, will pull A1C readings falsely low, potentially masking a real problem.
Sickle cell trait and other hemoglobin variants can also interfere with certain testing methods. If you have a known hemoglobin variant, kidney disease, or are on dialysis, your provider may rely more heavily on direct glucose testing or alternative markers rather than A1C alone.
What Happens if Prediabetes Goes Unchecked
Prediabetes is not a guaranteed path to diabetes, but the lifetime odds are significant. Research tracking adults from age 45 found that women with prediabetes had roughly a 58% lifetime risk of progressing to type 2 diabetes, while men had about a 46% risk. Over a shorter window of 10 years, the progression rate is lower, around 9% to 14% depending on sex, but those numbers climb steadily with time and inaction.
The damage doesn’t start only once you cross into diabetes territory, either. Prediabetic blood sugar levels are already high enough to begin stressing blood vessels and contributing to cardiovascular risk. That’s part of why catching it in this window matters so much.
How Much Lifestyle Changes Actually Help
The strongest evidence for reversing prediabetes comes from the Diabetes Prevention Program, a landmark study funded by the National Institutes of Health. Participants aimed for two specific targets: losing 7% of their body weight and getting 150 minutes of moderate exercise per week. After three years, those in the lifestyle group had reduced their risk of developing type 2 diabetes by 58% compared to a placebo group.
To put that weight loss target in practical terms, 7% of body weight for someone who weighs 200 pounds is 14 pounds. That’s a meaningful but achievable amount, and the study participants reached it through lower-fat, lower-calorie eating combined with activities like brisk walking. The exercise target works out to about 30 minutes a day, five days a week.
These results hold up even for people in the higher end of the prediabetes range. The key takeaway is that prediabetes is one of the few conditions where the progression is clearly modifiable. A1C levels can and do come back down into the normal range with sustained changes, particularly when weight loss and physical activity are combined.