The A1C range for prediabetes is 5.7% to 6.4%. An A1C below 5.7% is considered normal, and 6.5% or higher on two separate tests indicates type 2 diabetes. That 5.7% to 6.4% window is where your blood sugar is elevated enough to cause concern but not yet high enough for a diabetes diagnosis.
What the A1C Test Actually Measures
A1C reflects your average blood sugar over the past two to three months. Glucose in your bloodstream naturally attaches to hemoglobin, the protein inside red blood cells that carries oxygen. The more sugar in your blood, the more hemoglobin gets coated. Since red blood cells live for roughly 120 days, measuring how much glucose is stuck to them gives a reliable picture of your blood sugar patterns over that lifespan, rather than a single snapshot.
This is what makes A1C useful for spotting prediabetes. A fasting blood sugar test tells you what’s happening right now. A1C tells you what’s been happening for months. You don’t need to fast or prep for it, which also makes it one of the more convenient blood tests available.
Other Tests That Diagnose Prediabetes
A1C isn’t the only way to identify prediabetes. Two other common blood tests can flag the same condition, and your doctor may use one or more of them depending on your situation.
- Fasting blood sugar test: After at least 8 hours without eating or drinking, a result between 100 and 125 mg/dL falls in the prediabetes range. Below 100 is normal, and 126 or above suggests diabetes.
- Oral glucose tolerance test: You drink a sugary solution, then your blood sugar is checked two hours later. A reading between 140 and 199 mg/dL at the two-hour mark indicates prediabetes.
These tests sometimes tell slightly different stories. You could have a normal A1C but an elevated fasting glucose, or vice versa. That’s partly because each test captures a different aspect of how your body handles sugar. When results are borderline or conflicting, repeating the test or using a second method helps clarify the picture.
When A1C Results Can Be Misleading
Certain conditions can push your A1C reading higher or lower than your actual blood sugar levels would suggest. Iron deficiency anemia, which is common, tends to inflate A1C results. This is particularly relevant during late pregnancy, when iron stores often drop. Iron supplementation in these cases has been shown to lower A1C readings in both diabetic and non-diabetic individuals, confirming the distortion.
On the other side, anything that shortens the lifespan of red blood cells (such as blood loss or hemolytic anemia) can make A1C appear falsely low, because the hemoglobin hasn’t been circulating long enough to accumulate glucose. Kidney failure on dialysis can also cause A1C to underestimate true blood sugar levels. Certain inherited hemoglobin variants, including sickle cell trait, can also throw off the measurement depending on the testing method used.
If you have any of these conditions, a fasting glucose test or glucose tolerance test may give a more accurate read on your blood sugar status.
What Prediabetes Means for Your Health
Prediabetes isn’t just a warning label for future diabetes. Even before blood sugar crosses into the diabetic range, elevated levels can start damaging blood vessels, the heart, and the kidneys. Prediabetes has been linked to silent heart attacks, the kind that cause damage without the classic chest-clutching symptoms. So the harm isn’t theoretical or distant. It can begin while your numbers still look “borderline.”
The progression risk is real but not inevitable. A large study tracking adults from age 45 found that roughly half of women and just under half of men with prediabetes eventually developed type 2 diabetes over their remaining lifetime. The 10-year risk at that age was about 14% for women and 9% for men. Those numbers are significant, but they also mean that a large portion of people with prediabetes never progress, especially if they take action early.
How to Lower Your A1C
Prediabetes is one of the more reversible health conditions you can have. The CDC’s Diabetes Prevention Program, which has been studied extensively, targets two straightforward goals: losing 5% to 7% of your body weight and getting more physical activity. For someone who weighs 200 pounds, that’s a loss of 10 to 14 pounds. The program spreads this over 12 months, so it’s not a crash diet. It’s a gradual shift.
Physical activity improves how your cells respond to insulin, the hormone responsible for pulling sugar out of your blood. This effect kicks in quickly. A single session of moderate exercise (a brisk walk, cycling, swimming) improves insulin sensitivity for hours afterward. Consistent activity over weeks and months is what moves the A1C needle downward. The combination of modest weight loss and regular movement has been shown to cut the risk of progressing to type 2 diabetes by more than half in clinical trials.
Diet changes matter too, though the specifics are less important than the overall pattern. Reducing refined carbohydrates and sugary drinks, eating more fiber-rich foods, and watching portion sizes all contribute to better blood sugar control. You don’t need a specialized diet plan. Consistent, sustainable changes outperform aggressive short-term overhauls every time.
How Often to Retest
If your A1C comes back in the prediabetes range, retesting every one to two years helps track whether your numbers are holding steady, improving, or creeping upward. If you’re making lifestyle changes, you might see meaningful improvement within three to six months, since A1C reflects the previous two to three months of blood sugar. That makes it a useful feedback tool: each new result shows whether what you’re doing is working.
Keep in mind that A1C can sit in the prediabetes range for years without progressing. It’s not a countdown timer. Your next result depends far more on what you do between tests than on some fixed trajectory.