Prediabetes rarely announces itself with obvious symptoms. Most of the 98 million American adults who have it don’t know it. The most reliable way to find out is a simple blood test, but there are physical signs and risk factors that can tell you whether screening makes sense for you right now.
What the Blood Tests Actually Measure
Three blood tests can identify prediabetes, and any one of them is enough for a diagnosis. The most common is the A1C test, which measures your average blood sugar over the past two to three months. A result between 5.7% and 6.4% falls in the prediabetes range, and the higher you are within that window, the greater your risk of progressing to type 2 diabetes.
A fasting blood glucose test measures your blood sugar after you haven’t eaten for at least eight hours (usually done first thing in the morning). A result between 100 and 125 mg/dL indicates prediabetes. Below 100 is normal, and 126 or above on two separate tests points to diabetes.
The third option is an oral glucose tolerance test, where you drink a sugary solution and have your blood drawn two hours later. A reading between 140 and 199 mg/dL at the two-hour mark means prediabetes. This test is less commonly used for routine screening because it takes longer, but it can catch blood sugar problems the other tests miss.
Physical Signs Worth Paying Attention To
Prediabetes is sometimes called a “silent” condition because it produces no symptoms in most people. That said, there are a few physical changes that signal the insulin resistance driving prediabetes.
The most visible one is dark, thick, velvety patches of skin, a condition called acanthosis nigricans. These patches most often show up on the back of the neck, in the armpits, or in the groin. The affected skin may also feel itchy, develop an odor, or sprout small skin tags. If you’ve noticed darkened skin in these areas and haven’t been able to explain it, insulin resistance is a likely cause.
Some people also notice increased thirst, more frequent urination, or persistent fatigue, but these symptoms tend to be subtle enough that they’re easy to dismiss. They become more noticeable as blood sugar levels climb closer to the diabetic range. Blurred vision that comes and goes is another sign that blood sugar may be higher than it should be.
Who Should Get Screened
The U.S. Preventive Services Task Force recommends prediabetes screening for all adults aged 35 to 70 who are overweight or obese (a BMI of 25 or higher). If you’re Asian American, screening is recommended at a lower BMI of 23 or above, because the risk of insulin resistance rises at a lower weight in this population. Screening should also start earlier than 35 if you are American Indian, Alaska Native, Black, Hispanic or Latino, or Native Hawaiian or Pacific Islander, since these groups develop diabetes at disproportionately high rates.
Beyond age and weight, a few other risk factors make screening more urgent. Waist size matters independently of overall weight: the risk of insulin resistance increases for men with waists larger than 40 inches and women with waists larger than 35 inches. A family history of type 2 diabetes, a personal history of gestational diabetes, or a diagnosis of polycystic ovary syndrome all raise your risk as well. If any of these apply to you, it’s worth asking for an A1C or fasting glucose test even if you feel fine.
What Happens Inside Your Body
Prediabetes is fundamentally a problem of insulin resistance. When you eat, your body breaks food down into glucose, and your pancreas releases insulin to help move that glucose into your cells for energy. When your blood sugar stays elevated over long periods, your cells gradually stop responding to insulin as well as they should. Your pancreas compensates by producing even more insulin, trying to force blood sugar into reluctant cells.
For a while, this extra insulin keeps your blood sugar in a manageable range. But the pancreas can only compensate for so long. When it can no longer keep up with demand, blood sugar begins to rise and stays elevated. That’s prediabetes. If nothing changes, the pancreas continues to lose ground, and blood sugar eventually crosses the threshold into type 2 diabetes.
Can You Check at Home?
Over-the-counter A1C test kits exist, but their accuracy varies significantly. A University of Florida study tested several home kits against standard lab-drawn blood and found wide differences. One kit had 82% of its samples within the accepted accuracy range, while two others hit that benchmark in only 46% and 29% of samples. That margin of error is large enough to give you a falsely reassuring result or an unnecessarily alarming one.
Home kits can be useful as a rough check, but they’re not reliable enough to rule prediabetes in or out on their own. A lab test ordered through your doctor or a walk-in lab gives you a result you can actually act on with confidence.
Prediabetes Is Reversible
The most important thing about catching prediabetes early is that it responds well to lifestyle changes. A CDC-recognized lifestyle change program, which focuses on modest weight loss and regular physical activity, can cut your risk of developing type 2 diabetes in half. You don’t need to overhaul your life overnight. Losing 5% to 7% of your body weight (about 10 to 14 pounds for someone who weighs 200) and getting 150 minutes of moderate activity per week, something like brisk walking, is enough to make a measurable difference in how your body handles blood sugar.
The key is acting on the information once you have it. Prediabetes can stay stable or reverse entirely with sustained changes, but it can also progress silently if ignored. If your numbers come back in the prediabetes range, repeat testing every one to two years helps you track whether you’re heading in the right direction.