Prediabetes rarely announces itself with obvious symptoms, which is why most of the 98 million American adults who have it don’t know. The only reliable way to confirm prediabetes is a blood test, but certain physical signs, risk factors, and lifestyle patterns can tell you whether testing should be a priority. Here’s what to look for and what the numbers mean.
Why Prediabetes Is Easy to Miss
Prediabetes doesn’t usually cause symptoms you’d notice day to day. Unlike full-blown type 2 diabetes, where blood sugar climbs high enough to trigger obvious thirst, frequent urination, or blurred vision, prediabetes sits in a gray zone. Your blood sugar is above normal but not yet high enough to set off alarms. Most people feel completely fine, which is exactly why it goes undetected for years.
There is one visible clue worth checking for: darkened, velvety patches of skin in body creases like the neck, armpits, or groin. This condition, called acanthosis nigricans, is a direct sign of insulin resistance and commonly appears in people with prediabetes or obesity. The patches can also show up on elbows, knees, or hands. If you’ve noticed skin darkening in these areas that doesn’t wash off or fade, it’s worth mentioning to your doctor.
What’s Happening Inside Your Body
To understand prediabetes, it helps to know what insulin actually does. When you eat, your body breaks food into glucose (sugar) and releases it into your bloodstream. Your pancreas responds by producing insulin, a hormone that acts like a key, unlocking your cells so they can absorb that glucose for energy. In prediabetes, your cells start ignoring insulin’s signal. Your muscles, liver, and fat tissue become less responsive, a process called insulin resistance.
At first, your pancreas compensates by pumping out more insulin. This extra effort keeps blood sugar in a normal range for a while. But over time, the insulin-producing cells in your pancreas begin to wear down. They can’t keep up with the increased demand, and blood sugar starts creeping upward. This gradual decline in pancreas function is detectable in the prediabetes stage, well before type 2 diabetes develops. The process can unfold over years, giving you a real window to intervene.
Risk Factors That Raise Your Odds
Certain factors make prediabetes significantly more likely. You don’t need symptoms to warrant screening if several of these apply to you:
- Weight: Carrying extra weight, especially around the midsection, is the single strongest risk factor. Fat tissue in the abdomen releases inflammatory compounds that directly interfere with insulin signaling.
- Age: Risk increases after 35, which is why current screening guidelines now start at that age.
- Family history: A parent or sibling with type 2 diabetes raises your risk considerably.
- Ethnicity: Black, Hispanic, Native American, Asian American, and Pacific Islander populations face higher rates of prediabetes and type 2 diabetes.
- Physical inactivity: Sedentary habits reduce your muscles’ ability to use glucose efficiently.
- History of gestational diabetes: Developing diabetes during pregnancy signals underlying insulin resistance that persists after delivery.
- Polycystic ovary syndrome (PCOS): This hormonal condition is closely tied to insulin resistance, and women with PCOS are at elevated risk regardless of weight.
The Three Tests That Diagnose Prediabetes
A blood test is the only definitive way to know. Doctors typically use one of three options, and any single abnormal result is enough for a diagnosis.
The A1C test measures your average blood sugar over the past two to three months. It doesn’t require fasting and can be drawn at any time of day, making it the most convenient option. A result between 5.7% and 6.4% falls in the prediabetes range. Below 5.7% is normal; 6.5% or higher indicates type 2 diabetes.
The fasting plasma glucose test measures blood sugar after you haven’t eaten for at least eight hours. A result between 100 and 125 mg/dL signals prediabetes. At 126 mg/dL or above, on two separate tests, the diagnosis shifts to diabetes.
The oral glucose tolerance test is less common but more sensitive. You drink a sugary solution, then your blood sugar is measured two hours later. A reading between 140 and 199 mg/dL indicates prediabetes.
When to Get Screened
Both the U.S. Preventive Services Task Force and the American Diabetes Association recommend screening starting at age 35 for adults who are overweight or obese. The ADA goes further, recommending that all adults with overweight or obesity plus at least one additional risk factor get tested regardless of age. After an initial normal result, repeat screening every three years is the standard recommendation. If you have multiple risk factors or borderline results, your doctor may suggest testing more frequently.
Can You Test at Home?
Over-the-counter A1C test kits exist, but their accuracy varies widely. A University of Florida study compared several home A1C tests against standard lab results. The benchmark for accuracy is that a home test should land within 5% of the lab value at least 90% of the time. Only one product, Home Access, came close, with 82% of its samples meeting that standard. Two other FDA-cleared tests hit that accuracy mark in fewer than half their samples.
A home kit can give you a rough sense of where you stand, but it’s not reliable enough to rule prediabetes in or out on its own. If a home result comes back in the 5.7% to 6.4% range, or if you have risk factors, follow up with a lab test through your doctor.
What Happens If You Do Nothing
Prediabetes is not a guaranteed path to diabetes, but the odds aren’t in your favor without changes. Roughly 5 to 10% of people with prediabetes progress to type 2 diabetes each year. Within a decade, about 12.5% will have crossed that threshold. Over a full lifetime, up to 70% of people with prediabetes eventually develop type 2 diabetes.
The flip side of those numbers is encouraging. In the same large pooled analysis of 19 studies, 36% of people with prediabetes reverted to normal blood sugar within 10 years. Prediabetes is one of the few conditions where the trajectory is genuinely changeable.
How to Reverse Prediabetes
The most effective intervention isn’t medication. It’s a combination of regular exercise and modest weight loss. The target that research consistently supports is 150 minutes of moderate exercise per week (brisk walking counts) combined with losing at least 7% of your body weight if you’re overweight. For someone weighing 200 pounds, that’s 14 pounds.
In a major study tracking people with prediabetes, those who hit the 150-minute weekly exercise target were more than four times as likely to have normal blood sugar levels at their one-year follow-up compared to those who exercised less. About 58% of participants met that exercise goal, suggesting it’s achievable for most people with sustained effort.
Dietary changes that help the most include reducing refined carbohydrates (white bread, sugary drinks, processed snacks), increasing fiber intake through vegetables, legumes, and whole grains, and eating balanced meals that pair carbs with protein or fat to slow glucose absorption. You don’t need a radical overhaul. Consistent, moderate changes sustained over months produce measurable results in blood sugar levels.
The timeline for improvement varies, but many people see meaningful changes in A1C within three to six months of consistent lifestyle shifts. Your doctor will likely recheck your levels at that point to track progress.