A prediabetic A1c falls between 5.7% and 6.4%. Below 5.7% is considered normal, and 6.5% or higher crosses the threshold into type 2 diabetes. Both the American Diabetes Association and the CDC use these same cut-offs.
What the A1c Test Actually Measures
The A1c test works because glucose in your blood naturally sticks to hemoglobin, the protein inside red blood cells that carries oxygen. The more sugar circulating in your blood over time, the more hemoglobin gets coated. Since red blood cells live about three months, the test captures your average blood sugar over that entire window rather than a single snapshot of one morning.
This makes A1c especially useful for spotting patterns. A fasting glucose test tells you what your blood sugar is right now, which can fluctuate based on what you ate last night, how well you slept, or whether you’re stressed. The A1c smooths all of that out and gives a longer view.
The Prediabetes Range, Explained
A result of 5.7% means roughly 117 mg/dL as an estimated average blood sugar. At 6.4%, the upper boundary of prediabetes, the estimated average is around 137 mg/dL. The difference between those two numbers might sound small, but it represents a meaningful shift in how efficiently your body handles glucose.
Where you fall within that range matters. Someone at 5.8% is in a different position than someone at 6.3%. Higher values within the prediabetic range signal that the body’s ability to regulate blood sugar is deteriorating faster, and without changes, many people with prediabetes develop type 2 diabetes within five years.
Health Risks Start Before Diabetes
Prediabetes is sometimes dismissed as a warning that hasn’t become a real problem yet, but the cardiovascular data tells a different story. A large Canadian study of over 600,000 adults found that people with A1c levels of 6.0% to 6.4% had a significantly higher risk of being hospitalized for cardiovascular disease compared to people with normal levels. Men in that range had a 38% higher risk, and women had a 17% higher risk.
Perhaps more striking, men with A1c levels of 5.5% to 5.9%, a range still technically classified as normal, also showed elevated cardiovascular risk. This suggests that damage to blood vessels and the heart can begin well before someone officially crosses into diabetes territory. Prediabetes is not a waiting room. It’s a condition where harm is already accumulating.
Why A1c Doesn’t Catch Everything
The A1c test is convenient because it doesn’t require fasting, but it has a notable blind spot. Studies have found that an A1c of 6.5% identifies only about 30% to 40% of people who actually have undiagnosed diabetes. A fasting glucose test catches roughly 50%, and an oral glucose tolerance test, which measures how your body handles a sugar load over two hours, catches around 90%.
For prediabetes specifically, A1c performs even less reliably as a predictor of who will progress to diabetes compared to fasting glucose or glucose tolerance testing. This is why some doctors will order more than one type of test, especially if your A1c result is borderline or doesn’t match other signs.
Several medical conditions can also throw off A1c accuracy. Iron deficiency anemia pushes results artificially higher, which means you could get a prediabetic reading when your actual blood sugar control is normal. Late pregnancy has a similar effect due to iron changes. On the other hand, conditions that shorten the lifespan of red blood cells, like hemolytic anemia or recovery from significant blood loss, make A1c results falsely low. People with certain hemoglobin variants, including sickle cell trait, need their results interpreted with extra caution because the test may not reflect their true glucose levels.
What Moves the Number Down
The good news about prediabetes is that it responds well to lifestyle changes, often dramatically. The two biggest levers are weight loss and physical activity. Losing 5% to 7% of your body weight (roughly 10 to 14 pounds for someone who weighs 200) has been shown in large prevention trials to cut the risk of progressing to diabetes by more than half.
Exercise helps independently of weight loss. Regular physical activity improves how sensitive your cells are to insulin, which is the core problem driving blood sugar upward in prediabetes. Even moderate movement like brisk walking for 150 minutes per week makes a measurable difference.
Because A1c reflects a three-month average, you won’t see changes overnight. If you make significant dietary or activity changes today, your next A1c test in three months will begin to reflect those efforts. Many people are able to bring their number back below 5.7% and keep it there, effectively reversing prediabetes. The earlier you catch it within that 5.7% to 6.4% window, the easier that reversal tends to be.
How Often to Retest
If your A1c comes back in the prediabetic range, retesting every 6 to 12 months is typical. This frequency lets you track whether lifestyle changes are working or whether your numbers are creeping upward. If your result is at the higher end of the range, closer to 6.4%, your doctor may want to check more frequently or add a fasting glucose test for a fuller picture.
For people with normal results who have risk factors like a family history of diabetes, being over 45, or carrying extra weight around the midsection, periodic A1c screening every three years is a reasonable baseline. The test itself is a simple blood draw with no fasting required, which makes repeat testing straightforward.