Prediabetes is a condition where your blood sugar levels are higher than normal but not yet high enough to qualify as type 2 diabetes. It affects more than 115 million American adults, over 2 in 5, and 8 in 10 of them don’t know they have it. That gap between how common it is and how rarely it’s caught matters, because prediabetes is the stage where lifestyle changes are most effective at preventing progression to full diabetes.
How Prediabetes Is Diagnosed
Prediabetes is defined by three possible blood tests, and any one of them can confirm the diagnosis:
- A1C test: 5.7% to 6.4%. This measures your average blood sugar over the past two to three months.
- Fasting blood glucose: 100 to 125 mg/dL. This is a single blood draw after you haven’t eaten for at least eight hours.
- Oral glucose tolerance test: 140 to 199 mg/dL two hours after drinking a sugary solution. This measures how well your body handles a sudden spike in sugar.
Numbers below these ranges are considered normal. Numbers above them mean type 2 diabetes. The U.S. Preventive Services Task Force recommends screening for adults aged 35 to 70 who carry extra weight. If your results come back normal, repeating the test every three years is a reasonable schedule. People with risk factors may need earlier or more frequent testing.
What Happens Inside Your Body
Prediabetes is driven by two overlapping problems: your cells stop responding well to insulin, and your pancreas gradually loses the ability to compensate.
Insulin is the hormone that tells your cells to absorb sugar from the bloodstream. In a healthy body, the system works like a lock and key: insulin binds to receptors on your cells, triggering a chain reaction that pulls glucose inside. When you develop insulin resistance, that signaling process breaks down. The receptors may decrease in number, or the internal relay system inside the cell may malfunction. Either way, sugar stays in your blood longer than it should.
Your pancreas notices the rising blood sugar and tries to fix the problem by pumping out more insulin. For a while, this extra production keeps your levels in a normal range. But the insulin-producing cells (called beta cells) can only work that hard for so long. When they begin to fatigue and can’t keep pace with the demand, blood sugar starts creeping up, first into the prediabetic range and eventually, without intervention, into diabetic territory.
Excess body fat plays a central role. Fat tissue, especially around the midsection, triggers low-grade inflammation throughout the body, including in the liver, muscles, and pancreas. That chronic inflammation directly interferes with insulin signaling. Mitochondria, the structures inside cells that generate energy, also appear to function less efficiently in people with insulin resistance, which compounds the problem.
Who Is Most at Risk
Several factors raise your likelihood of developing prediabetes. Some you can change, others you can’t:
- Weight: Carrying extra weight, particularly around the abdomen, is the single most common driver of insulin resistance.
- Age: Risk increases at 45 and continues climbing.
- Family history: A parent or sibling with type 2 diabetes raises your odds significantly.
- Physical inactivity: Exercising fewer than three times a week is an independent risk factor.
- Ethnicity: African American, Hispanic/Latino, American Indian, Alaska Native, some Pacific Islander, and some Asian American populations face higher risk.
- History of gestational diabetes: Having had diabetes during pregnancy, or delivering a baby over 9 pounds, increases long-term risk.
- Non-alcoholic fatty liver disease: Fat buildup in the liver is closely tied to insulin resistance.
Having multiple risk factors doesn’t guarantee you’ll develop prediabetes, but it does mean screening is worth pursuing sooner rather than later.
Physical Signs You Might Notice
Prediabetes itself rarely causes obvious symptoms, which is why so many people have it without knowing. But insulin resistance can leave visible clues on the skin. The most recognizable is a condition called acanthosis nigricans: dark, thick, velvety patches of skin that typically appear in the armpits, groin, or on the back of the neck. The affected areas may feel slightly itchy, develop an odor, or produce small skin tags. These changes signal that insulin levels have been elevated for a prolonged period. If you notice these patches, they’re worth mentioning at your next appointment.
Health Risks Before Diabetes Develops
One common misconception is that prediabetes is harmless, just a warning sign with no real consequences until it becomes full diabetes. That’s not accurate. Damage to the cardiovascular system and kidneys can begin during the prediabetic stage.
People with prediabetes face a 15% greater risk for cardiovascular disease compared to those with normal blood sugar. Elevated blood sugar accelerates the buildup of fatty plaque in arteries, contributing to heart attacks and strokes. It also places extra strain on the kidneys, which work harder to filter excess sugar from the blood. Studies have found that people with prediabetes are up to twice as likely to develop chronic kidney disease, and the risk grows the longer blood sugar stays elevated.
Keeping blood pressure near 120/80 mmHg and LDL cholesterol at 70 mg/dL or below can offset much of that excess cardiovascular risk. These targets are tighter than what many people assume is “fine,” but for someone with prediabetes, the combination of slightly high blood sugar and slightly high cholesterol creates a compounding effect worth addressing early.
How Lifestyle Changes Reverse the Trend
The strongest evidence for preventing progression comes from the Diabetes Prevention Program, a large clinical trial that established two specific targets: lose 7% of your starting body weight, and get 150 minutes of moderate physical activity per week (roughly two and a half hours of brisk walking). Without intervention, many people with prediabetes develop type 2 diabetes within five years. The DPP showed that hitting those two targets cut that risk by 58%.
Seven percent of body weight is less than most people expect. For someone weighing 200 pounds, that’s 14 pounds. The study didn’t require extreme dieting or intense exercise. Brisk walking was the primary activity, and the calorie reduction was moderate. The key was consistency over months and years, not dramatic short-term effort.
These changes work because they directly address the underlying mechanism. Weight loss reduces the inflammation in fat tissue that disrupts insulin signaling. Exercise independently improves your cells’ ability to absorb glucose, even before significant weight loss occurs. Together, they give the pancreas breathing room, lowering the demand for insulin so beta cells aren’t driven to exhaustion.
When Medication Enters the Picture
For some people, lifestyle changes alone aren’t enough, or aren’t feasible at the intensity needed. Metformin, a medication that reduces the amount of sugar the liver releases into the bloodstream, is sometimes used alongside lifestyle changes for people with prediabetes. It has the strongest evidence of any medication for this purpose. In women with a history of gestational diabetes, metformin cuts the risk of progressing to type 2 diabetes by 50%, a benefit equal to lifestyle intervention alone in that group.
Metformin is not prescribed universally for prediabetes. It tends to be considered for people at particularly high risk: those with a BMI in the obese range, younger adults with prediabetes who have a long timeline ahead, or those whose blood sugar levels sit at the higher end of the prediabetic range and haven’t responded to lifestyle efforts. It works best as a complement to diet and activity changes, not a replacement.