Prediabetes is diagnosed when your blood sugar is higher than normal but not yet high enough to qualify as type 2 diabetes. The specific number depends on which test your doctor uses, but the most common threshold is an A1C of 5.7% to 6.4%. More than 115 million American adults have prediabetes, and 8 in 10 of them don’t know it, largely because the condition rarely causes noticeable symptoms.
The Three Tests and Their Ranges
There are three standard blood tests used to identify prediabetes, and each has its own set of numbers. Your doctor may use one or a combination.
A1C (hemoglobin A1C): This test measures your average blood sugar over the past two to three months, expressed as a percentage. It doesn’t require fasting, which makes it convenient. A normal A1C is below 5.7%. Prediabetes falls between 5.7% and 6.4%. An A1C of 6.5% or higher indicates type 2 diabetes.
Fasting blood sugar: This test measures your blood sugar after you haven’t eaten for at least eight hours. A normal fasting level is below 100 mg/dL. Prediabetes is 100 to 125 mg/dL. A reading of 126 mg/dL or higher on two separate occasions points to diabetes.
Oral glucose tolerance test (OGTT): For this test, your blood sugar is checked two hours after you drink a sugary solution. A normal two-hour reading is below 140 mg/dL. Prediabetes is 140 to 199 mg/dL. A result of 200 mg/dL or higher means diabetes.
Why the Numbers Differ Slightly by Organization
If you’ve seen slightly different numbers online, that’s because the two major health bodies don’t fully agree. The American Diabetes Association sets the fasting glucose cutoff for prediabetes at 100 mg/dL, while the World Health Organization uses a higher threshold of 110 mg/dL. Both organizations agree on the oral glucose tolerance range of 140 to 199 mg/dL. The WHO does not formally use the A1C test for prediabetes diagnosis, while the ADA considers 5.7% to 6.4% a defining criterion.
In the United States, most clinicians follow ADA guidelines, so the 100 mg/dL fasting threshold and the 5.7% A1C cutoff are the numbers you’re most likely to encounter.
What These Numbers Actually Mean in Your Body
A prediabetic blood sugar level signals that your body is starting to struggle with insulin, the hormone that moves sugar from your bloodstream into your cells. Either your cells are becoming resistant to insulin’s signal, or your pancreas isn’t producing quite enough of it. The result is that sugar lingers in your blood longer than it should after meals and even overnight.
This doesn’t mean damage is inevitable, but it does mean the process that leads to type 2 diabetes is already underway. Without changes to diet, activity level, or weight, 15% to 30% of people with prediabetes develop type 2 diabetes within five years.
Why Most People Don’t Know Their Numbers
Prediabetes is sometimes called a “silent” condition because it produces no reliable symptoms. Unlike full diabetes, which can cause increased thirst, frequent urination, and fatigue, prediabetes typically feels like nothing at all. That’s why the CDC estimates that 8 out of 10 people with prediabetes are unaware of it. The only way to catch it is through a blood test.
The U.S. Preventive Services Task Force recommends screening for prediabetes and type 2 diabetes in adults aged 35 to 70 who are overweight (a BMI of 25 or higher). If you’re Asian American, screening is recommended at a lower BMI of 23 or above. For people who are American Indian, Alaska Native, Black, Hispanic or Latino, or Native Hawaiian or Pacific Islander, screening at an earlier age is worth discussing with a doctor, since these groups face a higher baseline risk.
Bringing Your Numbers Back to Normal
Prediabetes is one of the few conditions where the trajectory can genuinely be reversed. The key target backed by clinical trial data is losing at least 5% to 7% of your body weight. For someone who weighs 200 pounds, that means losing 10 to 14 pounds. That number is deliberately modest because it’s achievable for most people through dietary changes and regular physical activity rather than extreme measures.
The results from two major clinical trials, the Diabetes Prevention Program and the Prediabetes Lifestyle Intervention Study, showed that people who lost more than 5% of their body weight through lifestyle changes saw their prediabetes go into remission 43% of the time. Those who achieved remission had a 73% lower risk of eventually developing type 2 diabetes compared to those who stayed in the prediabetic range. The combination that works best is consistent moderate exercise (around 150 minutes per week of something like brisk walking) paired with a diet lower in refined carbohydrates and added sugars.
If your A1C is on the higher end of the prediabetes range, closer to 6.4%, your doctor may recheck your levels every three to six months. If you’re closer to 5.7%, annual testing is typical. Either way, the numbers aren’t a permanent label. They’re a snapshot of where your blood sugar is right now, and they respond to changes you make.