Prediabetes is diagnosed when your blood sugar is higher than normal but not yet high enough to qualify as type 2 diabetes. The most commonly used marker is the A1C test, which measures your average blood sugar over the past two to three months. An A1C between 5.7% and 6.4% falls in the prediabetes range. Below 5.7% is considered normal, and 6.5% or higher indicates diabetes.
The Three Tests and Their Ranges
Doctors can diagnose prediabetes using any of three blood tests. Each measures blood sugar differently, and you only need one abnormal result to be classified as prediabetic.
- A1C test: 5.7% to 6.4%. This reflects your average blood sugar over roughly three months and doesn’t require fasting. It’s the most convenient option because you can take it at any time of day.
- Fasting blood sugar: 100 to 125 mg/dL. This is measured after at least eight hours without eating. A result of 126 mg/dL or higher on two separate tests means diabetes.
- Oral glucose tolerance test (OGTT): 140 to 199 mg/dL two hours after drinking a sugary solution. This test shows how efficiently your body processes a large dose of sugar. A reading of 200 mg/dL or above points to diabetes.
These ranges come from the American Diabetes Association’s diagnostic criteria. Your doctor may repeat the test to confirm the result, especially if you’re near a borderline number. It’s also possible to get a normal result on one test and a prediabetic result on another, since each captures a slightly different snapshot of how your body handles sugar.
What’s Happening in Your Body
Prediabetes develops when your cells start ignoring insulin, the hormone that moves sugar from your blood into your cells for energy. In the early stages, your pancreas compensates by pumping out more insulin to force sugar into resistant cells. This can work for a while, keeping blood sugar in the normal range. But over time, the pancreas can’t keep up with the increasing demand, and blood sugar begins to creep upward into the prediabetic zone.
This process, called insulin resistance, typically builds over years. You won’t feel it happening. There are no obvious symptoms at this stage, which is why 8 in 10 adults with prediabetes don’t know they have it. By the time blood sugar is elevated enough to show up on a test, the underlying resistance has usually been developing for a long time.
How Common Prediabetes Is
Over 115 million American adults, more than 2 in 5, currently have prediabetes. It’s far more common than most people realize, and the vast majority of those affected have never been told. Without intervention, roughly 5 to 10 percent of people with prediabetes progress to type 2 diabetes each year. That adds up quickly: within a decade, a substantial portion of untreated prediabetics will cross the threshold into diabetes.
Who Should Get Tested
The U.S. Preventive Services Task Force recommends screening for prediabetes in adults aged 35 to 70 who are overweight or obese (a BMI of 25 or higher). If you’re Asian American, the recommended threshold drops to a BMI of 23 because the risk of insulin resistance rises at a lower body weight in this population. Earlier screening is also recommended for Black, Hispanic/Latino, American Indian/Alaska Native, and Native Hawaiian/Pacific Islander adults, who develop diabetes at disproportionately high rates.
Outside of these formal guidelines, a family history of type 2 diabetes, a history of gestational diabetes during pregnancy, or conditions like polycystic ovary syndrome can all be reasons to test sooner. If your doctor orders routine bloodwork that includes a fasting glucose or A1C, prediabetes can show up even if that wasn’t the reason for the test.
Prediabetes Can Be Reversed
Unlike many chronic conditions, prediabetes is genuinely reversible. The landmark Diabetes Prevention Program trial found that losing 5 to 7 percent of body weight through calorie reduction and 150 minutes of moderate physical activity per week lowered the risk of developing type 2 diabetes by 58 percent. For people over 60, the risk dropped by 71 percent. Even 15 years later, participants who had made lifestyle changes still had a 27 percent lower rate of diabetes compared to those who hadn’t.
For someone weighing 200 pounds, 5 to 7 percent translates to a loss of just 10 to 14 pounds. That’s a realistic target, and it doesn’t require extreme dieting or intense exercise. Walking briskly for about 30 minutes five days a week meets the 150-minute threshold. The changes don’t have to be dramatic to shift your numbers back into the normal range.
When Medication Enters the Picture
Lifestyle changes are the first-line approach for prediabetes, but some people are also candidates for medication. Current guidelines suggest considering metformin for adults aged 25 to 59 with a BMI over 35, a fasting blood sugar above 110 mg/dL, an A1C above 6%, or a history of gestational diabetes. Metformin works by reducing the amount of sugar your liver releases into your bloodstream and by helping your cells respond better to insulin.
Medication isn’t a substitute for diet and exercise. In the same prevention trial, metformin alone reduced diabetes risk by about 31 percent, roughly half the benefit of lifestyle changes. For people who meet the criteria, combining both approaches provides the strongest protection. If your A1C is on the lower end of the prediabetic range, say 5.7% or 5.8%, lifestyle modifications alone are typically enough to bring it back to normal.