An A1C of 5.7% marks the beginning of the prediabetes range. It means your average blood sugar over the past two to three months has been higher than normal but not high enough to qualify as type 2 diabetes. In practical terms, it translates to an estimated average blood glucose of about 117 mg/dL, calculated using the standard formula (28.7 × A1C − 46.7 = eAG).
This result is a warning sign, not a diagnosis of diabetes. The normal range falls below 5.7%, prediabetes spans 5.7% to 6.4%, and diabetes is diagnosed at 6.5% or above. The higher your number within that prediabetes window, the greater your risk of progressing to type 2 diabetes.
What the A1C Test Actually Measures
The test measures how much glucose has attached to your red blood cells’ hemoglobin, the protein that carries oxygen through your bloodstream. Glucose sticks to hemoglobin through a natural chemical process, and once it binds, it stays attached for the life of that red blood cell. Since red blood cells live about 120 days on average, your A1C reflects a weighted picture of your blood sugar levels over roughly the past three months. It’s not an even average, though. About half of the result is driven by the most recent 30 days, another 40% comes from the month or two before that, and only about 10% reflects anything older than 90 days.
This is why the A1C is more useful than a single finger-stick glucose reading. A fasting glucose test captures one moment in time. The A1C captures the trend.
Why 5.7% Matters for Your Health
Prediabetes is often treated as a benign waiting room before diabetes, but that’s not quite right. Research shows that people who had prediabetes before eventually being diagnosed with type 2 diabetes already had significantly higher rates of early complications compared to those whose blood sugar was normal before diagnosis. Specifically, they had 76% higher odds of retinopathy (damage to blood vessels in the eyes) and 14% higher odds of nephropathy (early kidney damage). In other words, the damage doesn’t wait for a diabetes diagnosis to begin.
That said, 5.7% is the very bottom of the prediabetes range. Your risk is lower than someone sitting at 6.3%, and you have meaningful room to reverse course.
Factors That Can Skew Your Result
A 5.7% reading is generally reliable, but certain conditions can make it inaccurate. Anything that shortens the lifespan of your red blood cells, like hemolytic anemia or recent significant blood loss, will make your A1C appear falsely low because glucose has less time to accumulate on hemoglobin. On the other hand, iron deficiency anemia is associated with falsely elevated A1C readings, which means your actual blood sugar control could be better than the number suggests. This is particularly relevant for women in late pregnancy, where iron deficiency commonly pushes A1C higher even without diabetes.
Genetic hemoglobin variants, including sickle cell trait (HbS) and hemoglobin C trait (HbC), can also affect accuracy depending on the lab method used. Kidney disease, especially in patients on dialysis, tends to make A1C underestimate true blood sugar levels. If any of these apply to you, your doctor may use an alternative test, such as a fructosamine or glycated albumin test, to get a clearer picture.
What You Can Do to Lower It
The most well-studied approach to reversing prediabetes comes from the Diabetes Prevention Program, a landmark trial that established two concrete goals: lose 7% of your body weight and get about 150 minutes of moderate physical activity per week (roughly two and a half hours of brisk walking). Participants were encouraged to lose one to two pounds per week, reaching the 7% target within about 24 weeks. The activity goal was built up gradually over five weeks. These targets were chosen because previous studies showed they produced meaningful improvements in blood sugar, insulin sensitivity, and overall metabolic health.
For someone weighing 200 pounds, 7% means losing 14 pounds. That’s a realistic target over six months, and it was enough to cut the risk of progressing to type 2 diabetes by 58% in the trial.
Dietary Changes That Help
Beyond general calorie reduction, the type of carbohydrates you eat makes a measurable difference. A review of randomized controlled trials found that low glycemic index and low glycemic load diets consistently improved A1C, insulin resistance, and fasting insulin levels in people with prediabetes. Glycemic load accounts for both the quality and quantity of carbohydrates in a food. Foods with a glycemic load of 10 or below are considered low, 11 to 19 is medium, and 20 or above is high.
In practice, this means favoring whole grains over refined grains, eating legumes and non-starchy vegetables, pairing carbohydrates with protein or fat to slow absorption, and limiting sugary drinks and processed snacks. Many of the studies that showed glycemic improvements also found reductions in body weight, waist circumference, and body fat, which suggests these dietary changes work through multiple pathways at once.
How Often to Retest
The American Diabetes Association recommends retesting every one to two years once you’re in the prediabetes range. If you make significant lifestyle changes, your doctor may want to recheck sooner to see whether your numbers are moving in the right direction. Because the A1C is weighted toward the most recent month, you can start seeing improvements within three to four months of consistent changes. A drop from 5.7% back below that threshold is a realistic goal for many people with early prediabetes, particularly if weight loss and dietary shifts are sustained.