About 98 million American adults have prediabetes, and 81% of them don’t know it. That’s because prediabetes rarely causes obvious symptoms. Most people discover it through a routine blood test, not because something felt wrong. But there are risk factors, subtle physical signs, and simple screening tests that can tell you where you stand.
Why Prediabetes Is Easy to Miss
Prediabetes means your blood sugar is higher than normal but not yet high enough to qualify as type 2 diabetes. Your cells, particularly in your muscles, fat, and liver, stop responding well to insulin. When that happens, your pancreas pumps out more insulin to compensate. For a while, this keeps blood sugar in check. But over time, your pancreas can’t keep up, and glucose starts building in your blood.
This process unfolds gradually over months or years, and it doesn’t produce the dramatic thirst, frequent urination, or fatigue that full-blown diabetes causes. That’s why screening matters so much: by the time you feel something, you may already have crossed into diabetes territory.
Physical Signs That Suggest Insulin Resistance
One visible clue is a skin condition called acanthosis nigricans: dark, velvety patches that show up in body creases like the neck, armpits, or groin. They can also appear on the hands, elbows, or knees. These patches are a sign of insulin resistance and are common in people with obesity. Not everyone with prediabetes develops them, but if you notice darkened, thickened skin in those areas, it’s worth getting your blood sugar checked.
Beyond skin changes, prediabetes itself has few reliable symptoms. Some people report increased fatigue or slightly blurred vision, but these overlap with dozens of other conditions. The most useful indicators aren’t symptoms at all. They’re risk factors.
Risk Factors That Should Prompt Screening
The U.S. Preventive Services Task Force recommends screening for prediabetes and type 2 diabetes in adults aged 35 to 70 who are overweight or obese. But screening should start earlier if you belong to a group with higher incidence (American Indian/Alaska Native, Asian American, Black, Hispanic/Latino, or Native Hawaiian/Pacific Islander) or if you have a family history of diabetes, a history of gestational diabetes, or polycystic ovarian syndrome.
Body weight is one of the strongest predictors. A BMI of 25 or higher puts most adults at increased risk. For Asian Americans, that threshold is lower at 23. For Pacific Islanders, it’s 26. Waist circumference tells a similar story: men with a waist larger than 40 inches and women with a waist larger than 35 inches face higher risk, because fat stored around the midsection is closely tied to insulin resistance.
Other factors that raise your odds include being physically inactive, having high blood pressure or abnormal cholesterol levels, and being over 45. The more of these that apply to you, the more important it is to get tested rather than waiting for symptoms that may never come.
The Three Tests That Diagnose Prediabetes
Any of three standard blood tests can identify prediabetes. Your doctor will typically start with one and may confirm with another.
- A1C test. This measures your average blood sugar over the past two to three months. A result between 5.7% and 6.4% indicates prediabetes. It doesn’t require fasting, which makes it convenient.
- Fasting blood sugar test. After an overnight fast (at least eight hours), a blood draw measures your glucose level. A result between 100 and 125 mg/dL falls in the prediabetes range.
- Oral glucose tolerance test. You fast overnight, have your blood drawn, drink a sugary solution, then have your blood drawn again two hours later. A two-hour result between 140 and 199 mg/dL signals prediabetes.
If your results come back normal but you have risk factors, screening every three years is a reasonable schedule. If your numbers are borderline or you gain weight, your doctor may want to recheck sooner.
Are At-Home A1C Kits Reliable?
You can buy over-the-counter A1C test kits at most pharmacies, and they offer a general snapshot without a doctor’s visit. But their accuracy varies significantly. A University of Florida study tested several popular kits against standard lab results. To be considered reliable, at-home results should fall within 5% of the lab value at least 90% of the time. One kit (Home Access) met that bar 82% of the time, which is close but still short. Two other kits hit the mark in only 46% and 29% of samples.
An at-home kit can be a reasonable first step if you want to screen yourself before scheduling an appointment. But if your result is in the prediabetes range, or if it’s normal but you have several risk factors, a lab-grade test through your doctor is worth the confirmation. The stakes of a missed diagnosis are too high for a coin-flip test.
What Happens If You Don’t Address It
Prediabetes is not a guaranteed path to diabetes, but the risk is real. Research tracking a large population found that about 4% of people with prediabetes converted to type 2 diabetes within six months, and roughly 20% converted within four years. The good news is that conversion rates have been declining, dropping from about 8% per year in 2000 to 4% per year by 2014, likely because of increased awareness and earlier intervention.
Still, those numbers mean that without changes, about one in five people with prediabetes will develop type 2 diabetes within a few years. And the consequences extend beyond blood sugar. Prediabetes itself raises risk for heart disease, stroke, and kidney problems even before it crosses into full diabetes.
What Actually Works to Reverse It
Prediabetes is one of the few conditions where lifestyle changes are genuinely as effective as medication for most people. The landmark Diabetes Prevention Program trial established two targets that cut the risk of progressing to diabetes by 58%: losing 5% to 7% of your body weight (10 to 14 pounds for someone who weighs 200) and getting at least 150 minutes of moderate physical activity per week. That’s about 30 minutes a day, five days a week, of something like brisk walking.
You don’t need to overhaul everything at once. Small, consistent shifts in diet, particularly reducing refined carbohydrates and sugary drinks, combined with regular movement produce measurable results within months. Many people see their A1C drop back below 5.7% within a year. The CDC’s National Diabetes Prevention Program offers structured, year-long group programs available in person and online to help people hit those benchmarks with coaching and accountability.
For some people, particularly those whose blood sugar is closer to the diabetes threshold or who haven’t been able to make lifestyle changes stick, a doctor may also prescribe metformin. But for most, the combination of modest weight loss and regular exercise remains the most effective intervention available.