A prediabetic A1C is between 5.7% and 6.4%. This range means your average blood sugar over the past two to three months has been higher than normal but not yet high enough to qualify as type 2 diabetes, which starts at 6.5%. Below 5.7% is considered normal.
What the A1C Test Actually Measures
The A1C test works by measuring how much glucose has attached to your red blood cells. Specifically, it looks at the percentage of hemoglobin (the oxygen-carrying protein inside red blood cells) that has been coated with sugar. Because red blood cells live for about three months, the test captures a rolling average of your blood sugar rather than a single snapshot. That’s what makes it different from a finger-prick glucose reading, which only tells you what’s happening right now.
To put the numbers in more familiar terms, you can convert A1C into an estimated average glucose level. A 5.7% A1C translates to roughly 117 mg/dL, while a 6.4% A1C works out to about 137 mg/dL. For comparison, a diabetes-level A1C of 6.5% corresponds to around 140 mg/dL. The formula used is: (28.7 × A1C) − 46.7 = estimated average glucose in mg/dL.
Who Should Get Tested
The U.S. Preventive Services Task Force recommends screening for prediabetes in adults aged 35 to 70 who are overweight or obese. That starting age was recently lowered from 40 to 35. If you’re Asian American, screening is recommended at a lower BMI threshold (23 instead of 25), and if you’re American Indian, Alaska Native, Black, Hispanic/Latino, or Native Hawaiian/Pacific Islander, earlier screening may be appropriate because these populations have higher rates of diabetes.
If your result comes back in the prediabetic range, the CDC recommends repeating the A1C test every one to two years to track whether your levels are rising, holding steady, or improving.
What Prediabetes Means for Your Health
Prediabetes is not a guarantee that you’ll develop type 2 diabetes, but it is a strong warning signal. Your body is already struggling to manage blood sugar efficiently. In most cases, this happens because cells are becoming resistant to insulin, so the pancreas has to work harder to keep glucose levels in check. Over time, the pancreas can’t keep up, and blood sugar climbs into the diabetic range.
The progression isn’t inevitable, though. Prediabetes is the stage where lifestyle changes have the most impact. Weight loss is the single most effective lever. Losing even a modest amount of body weight, around 5% to 7%, can significantly improve how your body handles insulin. A structured program combining dietary changes with increased physical activity has been shown to reduce A1C by about 0.2% more than standard dietary advice alone, alongside meaningful weight loss. That may sound small, but when you’re sitting at 5.9% or 6.1%, a fraction of a percent can be the difference between moving toward diabetes or moving away from it.
When the A1C Test Can Be Wrong
The A1C test is reliable for most people, but certain conditions can throw off the results. Anything that changes how long your red blood cells survive or how hemoglobin behaves will affect accuracy.
- Iron-deficiency anemia can falsely raise your A1C because red blood cells live longer when iron is low, giving sugar more time to attach to hemoglobin.
- Chronic kidney disease can distort results in either direction.
- Heavy bleeding or conditions that shorten red blood cell lifespan can produce falsely low readings, potentially masking prediabetes or diabetes.
- Hemoglobin variants like sickle cell trait can cause results to read either too high or too low depending on the lab method used. People with sickle cell disease (HbSS, HbCC, or HbSC) should not rely on A1C testing at all, because ongoing anemia, red blood cell destruction, and transfusions make the test unreliable. Alternative blood sugar tests, like fructosamine, are used instead.
If you have any of these conditions and your A1C result seems inconsistent with your day-to-day glucose readings, the result may not reflect your true average. Your doctor can use a different type of blood sugar test to get a clearer picture.
How to Lower a Prediabetic A1C
The changes that bring A1C down are straightforward, though not always easy. Regular physical activity, even 150 minutes per week of brisk walking, improves insulin sensitivity. Reducing refined carbohydrates and added sugars helps blunt the blood sugar spikes that drive A1C upward. And weight loss, even a few kilograms, directly improves the body’s ability to regulate glucose.
Because A1C reflects a three-month average, you won’t see the effect of changes overnight. Most people need at least two to three months of consistent effort before a retest shows meaningful improvement. That delay can be frustrating, but it also means a single bad week won’t undo months of progress. The test smooths out the day-to-day noise and shows the overall trend, which is what matters most for long-term health.