An A1C level between 5.7% and 6.4% falls in the prediabetes range. Below 5.7% is considered normal, and 6.5% or higher indicates type 2 diabetes. This single blood test captures your average blood sugar over the past three months, making it one of the most reliable ways to spot blood sugar problems before they become full diabetes.
How the A1C Test Works
The A1C test measures how much sugar has attached to hemoglobin, the protein inside your red blood cells that carries oxygen. When blood sugar rises, glucose sticks to hemoglobin and stays there for the entire life of the cell. Since red blood cells live about three months, the test reflects your average blood sugar over that window. A higher percentage means more of your hemoglobin has been coated with glucose.
This is what makes A1C different from a finger-stick glucose reading, which only tells you what your blood sugar is right now. A single stressful morning or skipped meal can swing a glucose reading, but it won’t meaningfully change your A1C. That three-month average gives a much steadier picture of how your body is handling sugar overall.
What the Numbers Mean
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Type 2 diabetes: 6.5% or higher
Where you fall within the prediabetes range matters. Someone at 5.8% is in a very different position than someone at 6.3%. Research pooling data from 19 large studies found that people in the highest glucose quartile of prediabetes had a 16.1% chance of progressing to diabetes within 10 years, while their odds of reverting to normal blood sugar dropped to just 13.4%. In other words, the closer you are to 6.5%, the more urgently your body is signaling that something needs to change.
Other Tests That Diagnose Prediabetes
A1C isn’t the only option. Two other blood tests can confirm or complement the result:
- Fasting plasma glucose: You fast for at least eight hours, then have blood drawn. A result of 100 to 125 mg/dL indicates prediabetes.
- Oral glucose tolerance test (OGTT): You drink a sugary solution and have blood drawn two hours later. A result of 140 to 199 mg/dL at the two-hour mark signals prediabetes.
These tests sometimes disagree with each other. You might have a normal A1C but elevated fasting glucose, or vice versa. That’s because each test measures a slightly different aspect of how your body processes sugar. If one test comes back borderline, your doctor may order a second type to get a fuller picture.
When A1C Results Can Be Misleading
Because the test depends on hemoglobin and red blood cells behaving normally, certain conditions can throw off results. Anything that changes how long your red blood cells survive will skew the number. Certain anemias, significant kidney disease, and liver failure can all shorten or lengthen red blood cell lifespan, producing an A1C that doesn’t match your actual blood sugar levels.
Hemoglobin variants also affect accuracy. The most common ones, including sickle cell trait, hemoglobin C, hemoglobin E, and hemoglobin D, can cause falsely high or low readings depending on the lab method used. If you carry one of these variants, your doctor may rely more heavily on fasting glucose or the oral glucose tolerance test instead.
Why Prediabetes Isn’t Just a Warning Label
It’s tempting to treat prediabetes as a yellow light, something to keep an eye on but not worry about yet. The data suggest otherwise. Up to 70% of people with prediabetes eventually develop type 2 diabetes, with roughly 5 to 10% crossing that threshold each year. Within a decade, about 1 in 8 people with prediabetes will have progressed to diabetes. Only about 1 in 3 will revert to normal blood sugar on their own.
Damage can also start before a diabetes diagnosis arrives. A large study found that one quarter of people with prediabetes already had signs of eye disease, kidney disease, or heart disease at the time they were diagnosed with diabetes. People who had prediabetes in the three years before their diabetes diagnosis were 75% more likely to have eye disease than people whose blood sugar had been normal. The small blood vessels in your eyes, kidneys, and nerves are sensitive to elevated glucose, and they don’t wait for an official diagnosis to start deteriorating.
Who Should Get Screened
The U.S. Preventive Services Task Force recommends screening for prediabetes and type 2 diabetes in adults aged 35 to 70 who are overweight or obese (a BMI of 25 or higher). If you’re Asian American, screening is recommended at a lower BMI of 23, because the risk of insulin resistance rises at a lower body weight in this population. For people who are American Indian, Alaska Native, Black, Hispanic or Latino, or Native Hawaiian or Pacific Islander, earlier screening before age 35 is worth discussing, since these groups develop diabetes at disproportionately high rates.
If you have a family history of type 2 diabetes, a history of gestational diabetes, or polycystic ovary syndrome, you may also benefit from earlier or more frequent testing regardless of your age or weight.
Lowering Your A1C Back to Normal
Prediabetes is one of the most reversible chronic conditions in medicine, and the evidence for how to do it is strong. The landmark Diabetes Prevention Program study found that a structured lifestyle change focusing on two goals, losing 5 to 7% of body weight and getting at least 150 minutes of moderate physical activity per week, reduced the risk of developing type 2 diabetes by 58%. For someone weighing 200 pounds, that’s a loss of 10 to 14 pounds.
That 150 minutes per week works out to about 30 minutes of brisk walking five days a week. It doesn’t need to be intense exercise. Walking, cycling, swimming, or any activity that gets your heart rate up counts. The weight loss component came primarily from reducing overall calorie intake rather than following any specific diet. Small, sustained changes outperformed dramatic short-term efforts.
The CDC’s National Diabetes Prevention Program offers year-long group programs based on this research, available in person and online across the country. Participants work with a lifestyle coach and a peer group, which helps with accountability. The structure matters: people in guided programs consistently outperform those trying to make the same changes alone.
If your A1C is at the higher end of the prediabetes range, closer to 6.4%, your doctor may also discuss medication alongside lifestyle changes. But for most people in the prediabetes range, the combination of modest weight loss and regular physical activity is the most effective intervention available.