Prediabetes means your blood sugar is higher than normal but not yet high enough to qualify as type 2 diabetes. It affects an estimated 115 million American adults, and 8 in 10 of them don’t know they have it. That gap between having the condition and knowing about it matters, because prediabetes is the stage where lifestyle changes can make the biggest difference.
How Prediabetes Is Diagnosed
Three common blood tests can identify prediabetes, and any one of them is enough for a diagnosis:
- A1C test: 5.7% to 6.4%. This measures your average blood sugar over the past two to three months.
- Fasting blood sugar: 100 to 125 mg/dL. You fast overnight and have blood drawn in the morning.
- Glucose tolerance test: 140 to 199 mg/dL at the two-hour mark. You drink a sugary solution, then your blood is tested two hours later to see how efficiently your body processes it.
Below these ranges is normal. At or above the upper end, you’d be diagnosed with type 2 diabetes. The U.S. Preventive Services Task Force recommends screening for adults aged 35 to 70 who have overweight or obesity, though your doctor may test earlier if you have other risk factors.
What Happens Inside Your Body
Prediabetes is driven by two problems that reinforce each other: insulin resistance and strain on the cells that produce insulin.
Insulin is the hormone that moves sugar from your blood into your cells for energy. When your cells stop responding to insulin efficiently, your pancreas compensates by pumping out more of it. For a while, this extra insulin keeps your blood sugar in a normal range. But over time, the constant overproduction wears down the insulin-producing cells in your pancreas. They start to falter, and blood sugar begins to creep up. That’s the prediabetes window: your body is still compensating, but the system is under strain. Excess sugar and fat in the bloodstream further damage those overworked cells, creating a cycle that, left unchecked, leads to type 2 diabetes.
Why Most People Don’t Know They Have It
Prediabetes rarely causes obvious symptoms, which is why the vast majority of people with the condition are unaware. You can have elevated blood sugar for years without feeling different.
One physical sign worth knowing about is dark, thick, velvety patches of skin that develop in body folds, particularly the armpits, groin, and back of the neck. This skin change is strongly linked to insulin resistance. The patches develop slowly, may feel itchy, and sometimes have a slight odor or develop small skin tags. Not everyone with prediabetes gets these patches, but if you notice them, they’re worth mentioning to your doctor.
Who Is Most at Risk
Several factors raise your likelihood of developing prediabetes:
- Weight: Having overweight or obesity is the single strongest risk factor.
- Age: Risk increases at 35 and continues climbing.
- Family history: A parent or sibling with type 2 diabetes raises your odds.
- Activity level: Being physically active fewer than three times a week.
- Pregnancy history: Having had gestational diabetes or delivering a baby over 9 pounds.
- Liver health: Non-alcoholic fatty liver disease is independently linked to insulin resistance.
- Ethnicity: African American, Hispanic or Latino, American Indian, Alaska Native, some Pacific Islander, and some Asian American populations face higher risk.
These factors are cumulative. A 40-year-old with a family history of diabetes who exercises rarely carries more risk than someone with just one of those factors alone.
The Damage Can Start Before Diabetes
A common misconception is that prediabetes is harmless, just a warning label. In reality, the elevated blood sugar during this stage can already begin affecting your body. Studies of people newly diagnosed with type 2 diabetes have found that those who had prediabetes beforehand had 76% higher odds of early-stage eye damage (retinopathy) and 14% higher odds of early kidney damage compared to people whose blood sugar had been normal. They also had a 7% increase in the odds of acute coronary syndrome, a serious heart condition.
These complications are generally milder than what develops with full diabetes, but they demonstrate that the damage doesn’t wait for an official diabetes diagnosis to begin. Blood vessels, nerves, and organs are sensitive to even modestly elevated sugar levels over time.
How Likely Prediabetes Progresses to Diabetes
Without lifestyle changes, 15% to 30% of people with prediabetes will develop type 2 diabetes within five years. That’s a wide range because individual risk depends heavily on where your numbers fall, how many risk factors you carry, and whether your condition is trending upward or staying stable.
The flip side of that statistic is important: most people with prediabetes don’t progress within that window, especially if they take action. Prediabetes is not a guarantee of diabetes. It’s a signal that your metabolism is heading in a direction you want to redirect.
What Actually Works to Reverse It
The most convincing evidence comes from the Diabetes Prevention Program, a landmark study that tested whether structured lifestyle changes could prevent type 2 diabetes in high-risk adults. Participants who lost 5% to 7% of their body weight (10 to 14 pounds for someone weighing 200 pounds) and added moderate physical activity reduced their risk of developing type 2 diabetes by 58%. That’s a larger reduction than any medication tested in the same study.
The physical activity target was 150 minutes per week of moderate exercise, which works out to about 30 minutes a day, five days a week. Walking counts. The weight loss didn’t require extreme dieting. Small, sustained changes in portion size and food choices were enough for most participants to hit the 5% to 7% target.
These results led the CDC to create the National Diabetes Prevention Program, a structured year-long program available across the country through community organizations, health systems, and online platforms. It pairs group coaching with gradual behavior changes rather than dramatic overhauls. If you’ve been told you have prediabetes, these programs are specifically designed for you and are often covered by insurance.
What to Expect After a Diagnosis
If your blood work comes back in the prediabetes range, your doctor will typically recommend retesting in one to three years to track your trajectory, sooner if you have multiple risk factors. The A1C test is the most convenient for monitoring because it doesn’t require fasting and captures a longer window of blood sugar behavior.
Your numbers can genuinely return to normal. Prediabetes is one of the few conditions where the trajectory is reversible with changes that don’t involve medication for most people. The key is catching it, which is why screening matters, and then treating it as the actionable warning it is rather than something to worry about later.