Prediabetes means your blood sugar is higher than normal but not yet high enough to qualify as type 2 diabetes. It’s a warning stage, not a diagnosis of diabetes itself, and it affects roughly 1 in 3 American adults. The good news: prediabetes is reversible with lifestyle changes, and catching it early can prevent or significantly delay the progression to full diabetes.
How Prediabetes Is Defined by the Numbers
Doctors diagnose prediabetes using one of three blood tests, each with a specific range that falls between “normal” and “diabetic.”
- A1C test: 5.7% to 6.4% (this reflects your average blood sugar over the past two to three months)
- Fasting blood sugar: 100 to 125 mg/dL (measured after not eating for at least eight hours)
- Oral glucose tolerance test: 140 to 199 mg/dL two hours after drinking a sugary solution
Any result above these ranges points to type 2 diabetes. Any result below them is considered normal. Prediabetes sits in that middle zone, and a single test in that range is usually enough for a diagnosis, though your doctor may repeat the test to confirm.
What’s Happening Inside Your Body
To understand prediabetes, it helps to know how your body normally handles sugar. When you eat, your digestive system breaks food into glucose, which enters your bloodstream. Your pancreas then releases insulin, a hormone that acts like a key, unlocking your cells so they can absorb that glucose for energy.
In prediabetes, two things start to go wrong at the same time. First, your cells, particularly in your muscles and liver, become less responsive to insulin. This is called insulin resistance. Your liver, which normally stores and releases glucose in a regulated way, may start dumping too much sugar into your blood between meals. Meanwhile, your muscle cells don’t absorb glucose as efficiently after you eat.
Second, your pancreas can’t fully compensate. Healthy insulin-producing cells would ramp up production to overcome the resistance, but in prediabetes, the early burst of insulin your pancreas releases after a meal is already blunted. Research published in Diabetes Care found that this decline in insulin function starts surprisingly early, even before blood sugar crosses into the official prediabetes range. The drop in first-phase insulin secretion begins when fasting glucose rises above just 90 mg/dL, well within what’s considered “normal.”
This means prediabetes isn’t a switch that flips. It’s a gradual process where your body’s ability to manage sugar slowly erodes over months and years.
Why Most People Don’t Know They Have It
Prediabetes rarely causes symptoms you’d notice. You won’t feel your blood sugar creeping up from 95 to 110 mg/dL. That’s why screening matters and why so many people are caught off guard by the diagnosis.
One visible sign worth knowing about: dark, thick, velvety patches of skin, most commonly in the armpits, groin, or back of the neck. This condition, called acanthosis nigricans, is strongly linked to insulin resistance. The patches develop slowly and may be itchy or have a slight odor. If you notice this kind of skin change, it’s a meaningful signal that your body is struggling with insulin, even if you feel fine otherwise.
Who’s at Higher Risk
Weight is the single strongest risk factor. The more fat tissue you carry, especially around your abdomen, the more resistant your cells tend to become to insulin. A waistline over 40 inches in men or 35 inches in women is a red flag. But prediabetes isn’t exclusively a weight issue. People with normal weight can develop it too, particularly if other risk factors are present.
Those other factors include being over 45, having a parent or sibling with type 2 diabetes, and belonging to certain ethnic groups. Black, Hispanic, American Indian, Asian American, and Native Hawaiian or Pacific Islander populations all face disproportionately higher rates, though the biological reasons aren’t fully understood. A history of gestational diabetes raises your risk as well, and so does polycystic ovary syndrome (PCOS).
Smoking increases risk, as do certain medications like steroids, antipsychotics, and some HIV treatments. Medical conditions tied to insulin resistance, including obstructive sleep apnea, fatty liver disease, and Cushing’s syndrome, also make prediabetes more likely.
The US Preventive Services Task Force recommends screening for adults aged 35 to 70 who are overweight or obese. If you’re from a higher-risk ethnic group, screening should start earlier. For Asian Americans, a lower BMI threshold of 23 (rather than the usual 25) is used because metabolic risks appear at lower body weights in this population.
Damage Can Start Before Diabetes
One of the most important things to understand about prediabetes is that it’s not a harmless waiting room. Damage to your smallest blood vessels, the ones that supply your eyes, kidneys, nerves, and heart, can begin during the prediabetic stage itself.
A large study published in Circulation by the American Heart Association found that people with prediabetes already showed measurable declines in the function of these tiny blood vessels compared to people with normal blood sugar. The small arteries in the eyes of people with prediabetes dilated less effectively, and blood flow responses in the skin were reduced. The impairment was roughly one-quarter to one-half as severe as what’s seen in people with established type 2 diabetes.
This matters because it means the cardiovascular damage traditionally associated with diabetes, including increased risk of heart failure, stroke, kidney problems, and cognitive decline, doesn’t wait for a diabetes diagnosis to begin. It starts accumulating during prediabetes. That’s a strong reason to take the diagnosis seriously rather than treating it as a “borderline” result that doesn’t require action.
How Likely Prediabetes Is to Become Diabetes
Without intervention, roughly 5 to 10% of people with prediabetes progress to type 2 diabetes each year. Over a decade, about 12.5% will have made that transition. Those numbers may sound modest, but they compound over time, and the risk is higher for people with additional risk factors or A1C values closer to the diabetic threshold.
The flip side is encouraging: prediabetes can return to normal blood sugar levels. Not everyone progresses. A significant number of people revert to normal glucose metabolism, especially with lifestyle changes.
Reversing Prediabetes With Lifestyle Changes
The landmark Diabetes Prevention Program trial established a clear formula that remains the gold standard. Participants who made modest lifestyle changes reduced their risk of developing type 2 diabetes by 58%. The targets were straightforward: 150 minutes of moderate physical activity per week (like brisk walking, about 30 minutes five days a week), reduced intake of simple carbohydrates, higher fiber intake, and a weight loss goal of 7% of body weight for those who were overweight.
For someone weighing 200 pounds, that’s 14 pounds. It doesn’t require reaching an “ideal” weight. That relatively small amount of weight loss produced dramatic results in the study, and physical activity provided benefits even independent of weight loss. Exercise improves your muscles’ ability to absorb glucose and reduces insulin resistance directly.
These changes don’t need to happen all at once. Gradual, sustained adjustments work better than aggressive short-term diets. The key is consistency over months and years, not perfection in any given week. Regular follow-up testing, typically every one to three years, lets you and your doctor track whether your blood sugar is moving in the right direction.