Prediabetes means your blood sugar is higher than normal but not yet high enough to qualify as type 2 diabetes. It’s diagnosed when your A1C falls between 5.7% and 6.4%, your fasting blood sugar is 100 to 125 mg/dL, or your two-hour glucose tolerance result lands between 140 and 199 mg/dL. More than 115 million American adults, roughly 2 in 5, currently have prediabetes, and 8 in 10 of them don’t know it.
The Three Tests and Their Numbers
Doctors can diagnose prediabetes with any of three blood tests. Each measures blood sugar differently, and hitting the prediabetic range on just one of them is enough for a diagnosis.
- A1C: This reflects your average blood sugar over the past two to three months. Normal is below 5.7%. Prediabetes is 5.7% to 6.4%. At 6.5% or higher, it’s diabetes.
- Fasting plasma glucose: Taken after at least eight hours without eating. Normal is below 100 mg/dL. Prediabetes is 100 to 125 mg/dL. At 126 mg/dL or above, it’s diabetes.
- Oral glucose tolerance test (OGTT): You drink a sugary solution, then your blood sugar is checked two hours later. Normal is below 140 mg/dL. Prediabetes is 140 to 199 mg/dL. At 200 mg/dL or higher, it’s diabetes.
Your doctor may use any of these tests, though A1C is the most common for routine screening because it doesn’t require fasting. If your result is borderline, you may be asked to repeat the test or take a different one to confirm.
Why Most People Don’t Notice It
Prediabetes rarely causes obvious symptoms. You can carry elevated blood sugar for years without feeling different, which is why the vast majority of people who have it are unaware. The one visible clue that sometimes appears is a patch of darkened, velvety skin, typically on the back of the neck, in the armpits, or in the groin. This skin change is linked to insulin resistance and tends to develop gradually, so it’s easy to overlook or attribute to something else.
What’s Happening Inside Your Body
In a healthy metabolism, insulin acts like a key that unlocks your cells so they can absorb sugar from the bloodstream. Prediabetes develops when that system starts breaking down in two ways at once.
First, your cells become resistant to insulin. Excess fat, particularly around the liver and muscles, interferes with insulin’s ability to do its job. Fat buildup in the liver shifts the way lipids are processed, producing molecules that block insulin signaling. In muscle tissue, incomplete fat metabolism creates similar interference. The result is that your cells stop responding efficiently to insulin, so sugar stays in the blood longer than it should.
Second, the insulin-producing cells in your pancreas start to struggle. They’re forced to work harder and produce more insulin to compensate for the resistance. Over time, this chronic overwork causes stress and damage to those cells, reducing their ability to keep up with demand. When the pancreas can no longer compensate for the resistance, blood sugar climbs into the prediabetic range and, eventually, into diabetic territory.
Who Should Be Screened
The U.S. Preventive Services Task Force recommends screening for prediabetes in adults aged 35 to 70 who are overweight or obese. The American Diabetes Association casts a slightly wider net, recommending universal screening for everyone 45 and older regardless of weight, plus screening at any age for adults who are overweight and have at least one additional risk factor.
Those risk factors include having a parent or sibling with type 2 diabetes, being physically active fewer than three times a week, having a history of gestational diabetes or delivering a baby over 9 pounds, and having non-alcoholic fatty liver disease. African American, Hispanic, American Indian, Alaska Native, and some Asian American and Pacific Islander populations face disproportionately higher risk, so earlier screening (and screening at lower BMI thresholds) is appropriate. For Asian Americans specifically, guidelines suggest using a BMI cutoff of 23 rather than the standard 25.
If your results come back normal, repeating the test every three years is a reasonable schedule.
Prediabetes Carries Real Health Risks
It’s tempting to treat prediabetes as a “pre” condition that only matters if it progresses to full diabetes. Recent evidence shows that’s not the case. A large study published in Diabetologia found that people with prediabetes had a 38% higher risk of heart disease and stroke, a 37% higher risk of heart failure, and a 25% higher risk of chronic kidney disease compared to people with normal blood sugar. These elevated risks persisted even when researchers accounted for whether someone eventually developed diabetes. In fact, progression to diabetes explained less than a quarter of the excess risk. In other words, prediabetic blood sugar levels are doing damage on their own.
How Weight Loss and Exercise Change the Outcome
The most powerful evidence for reversing prediabetes comes from the Diabetes Prevention Program, a landmark trial involving over 1,000 participants across 27 centers. The lifestyle intervention had two straightforward goals: lose 7% of body weight and get 150 minutes of moderate physical activity per week, roughly 30 minutes of brisk walking five days a week. Participants who hit those targets reduced their risk of developing type 2 diabetes by 58%. A follow-up study from Johns Hopkins found that modest weight loss through healthy eating and exercise delayed the onset of type 2 diabetes by 34% over four years.
Seven percent of body weight is about 14 pounds for someone who weighs 200 pounds. That’s a meaningful but achievable target, and you don’t need to lose it all at once. Even partial progress toward these goals lowers risk.
What to Eat With Prediabetes
The Mediterranean diet is widely considered the best eating pattern for prediabetes, emphasizing whole grains, lean protein, healthy fats, and plenty of vegetables. A practical way to build meals is to fill half your plate with nonstarchy vegetables like leafy greens, a quarter with whole grains such as brown rice or quinoa, and a quarter with lean protein like chicken, fish, or tofu.
Fiber is especially important because it slows the absorption of sugar into your bloodstream. Aim for 25 to 30 grams per day from a variety of fruits, vegetables, and whole grains. Limiting saturated and trans fats by choosing lean cuts of meat and low-fat dairy also helps improve insulin sensitivity over time. These aren’t temporary restrictions. The people in prevention trials who sustained their habits saw the most lasting benefits.
When Medication Enters the Picture
For some people, lifestyle changes alone may not be enough, or the risk of progression is high enough that medication makes sense alongside diet and exercise. The American Diabetes Association’s 2025 guidelines recommend considering metformin for adults aged 25 to 59 with a BMI of 35 or higher, a fasting glucose of 110 mg/dL or above, an A1C of 6.0% or higher, 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. It’s not a substitute for lifestyle changes but rather an addition when the numbers suggest a higher probability of progressing to diabetes.