Prediabetes usually has no noticeable symptoms, which is exactly why most people who have it don’t know. About 98 million American adults have prediabetes, and the only reliable way to confirm it is through a blood test. The good news is that testing is simple, and catching it early gives you a real window to reverse course before it becomes type 2 diabetes.
Why Prediabetes Is Hard to Feel
Unlike full type 2 diabetes, prediabetes rarely causes the classic warning signs people associate with blood sugar problems. You won’t typically notice increased thirst, frequent urination, or blurred vision at this stage. Those symptoms tend to appear after blood sugar has climbed high enough to cross into diabetes territory. Prediabetes is what’s happening underneath: your body is producing more and more insulin to keep blood sugar in check, but the system is starting to strain.
Here’s what’s going on inside. Your pancreas releases insulin to move sugar from your blood into your cells. In prediabetes, your cells gradually stop responding to insulin as well as they should. Your pancreas compensates by pumping out even more insulin, which paradoxically makes the problem worse over time. The excess insulin causes your cells to pull even more of their insulin receptors off the surface, further reducing their sensitivity. It’s a feedback loop: more insulin leads to more resistance, which leads to more insulin. Eventually, your pancreas can’t keep up, and blood sugar starts rising.
Physical Clues Worth Checking
While most people feel perfectly fine, there is one visible sign strongly linked to the insulin resistance behind prediabetes: dark, velvety patches of skin in body creases. This condition, called acanthosis nigricans, most commonly appears on the neck, armpits, or groin, though it can also show up on your elbows, knees, or hands. These patches aren’t just dry skin. They’re a direct signal that your body is producing unusually high levels of insulin. If you notice this kind of skin darkening, it’s worth getting your blood sugar checked.
Skin tags, particularly clusters of them around the neck or armpits, are another soft indicator of insulin resistance, though they’re less specific on their own.
The Three Blood Tests That Diagnose It
A diagnosis comes down to one of three standard blood tests. Your doctor may order any of them, and sometimes more than one to confirm.
A1C test: This measures your average blood sugar over the past two to three months. It doesn’t require fasting. A normal result is below 5.7%. Prediabetes falls between 5.7% and 6.4%. At 6.5% or above, it’s diabetes.
Fasting plasma glucose: This measures your blood sugar after at least eight hours without eating. Normal is below 100 mg/dL. Prediabetes ranges from 100 to 125 mg/dL. At 126 mg/dL or above, it’s diabetes.
Oral glucose tolerance test: You drink a sugary solution, and your blood sugar is measured two hours later. Normal is below 140 mg/dL. Prediabetes is 140 to 199 mg/dL. Diabetes is 200 mg/dL or above.
The A1C is the most convenient since it doesn’t require fasting or waiting around a lab for two hours. It’s also the most commonly used for initial screening.
Can You Test at Home?
Home A1C kits are available over the counter, but their accuracy varies significantly. A 2022 study tested three commercial home-use A1C kits against lab reference values. The best performer matched the lab result within an acceptable margin 82% of the time. The worst matched only 29% of the time. None of the three met the national standardization goal of 90% accuracy. More than half of the samples from two of the kits were off by more than 0.5 percentage points, which is enough to misclassify someone as normal when they’re actually prediabetic, or vice versa.
A home kit can give you a rough idea, but if the result is anywhere near the prediabetic range, get a lab test to confirm. The difference between 5.6% and 5.8% matters here, and home kits aren’t precise enough to make that call reliably.
Risk Factors That Should Prompt Testing
Screening is generally recommended starting at age 35, or earlier if you have additional risk factors. The more of these that apply to you, the stronger the case for getting tested:
- Weight: Carrying extra weight, particularly around the midsection, is the single strongest risk factor. A waist circumference above 40 inches for men or 35 inches for women significantly increases risk.
- Family history: A parent or sibling with type 2 diabetes raises your odds considerably.
- Physical inactivity: Being active fewer than three times a week is an independent risk factor.
- History of gestational diabetes: If you developed diabetes during pregnancy, your long-term risk is elevated.
- Polycystic ovary syndrome (PCOS): This condition is closely tied to insulin resistance.
- Ethnicity: Risk varies across populations. Black, Hispanic, Native American, Asian American, and Pacific Islander individuals face higher rates of progression to type 2 diabetes.
- Age: Risk rises after 35 and continues climbing, partly because muscle mass tends to decline and body fat increases with age.
If none of these apply and your initial screening is normal, repeating the test every three years is reasonable. If you have multiple risk factors, testing every one to two years gives you a better safety net.
How Quickly Prediabetes Becomes Diabetes
Without any changes, roughly 5 to 10% of people with prediabetes progress to full type 2 diabetes each year. That rate varies depending on how high your numbers already are, your weight, and your genetics, but the math is straightforward: within a decade, a substantial percentage of people with untreated prediabetes will have diabetes.
The flip side is encouraging. Prediabetes is one of the most reversible conditions in medicine. 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, like brisk walking, reduces the risk of progressing to diabetes by 58%. That number comes from one of the largest diabetes prevention trials ever conducted, and the results have held up across age groups and ethnic backgrounds.
The changes don’t need to be dramatic. Consistent moderate improvements in diet and activity level are what drive results. People who make these shifts sometimes bring their A1C back below 5.7%, effectively returning to normal blood sugar regulation.
What to Watch For if You’re Already Prediabetic
If you’ve been told you have prediabetes, the symptoms of progression toward type 2 diabetes are worth knowing. Increased thirst and frequent urination are the earliest and most common signs that blood sugar is climbing beyond the prediabetic range. Persistent fatigue that doesn’t improve with sleep, blurred vision, and slow-healing cuts or sores also signal worsening blood sugar control. Numbness or tingling in your hands or feet suggests nerve involvement, which typically means blood sugar has been elevated for a while.
Any of these developing in someone with known prediabetes warrants a new round of testing rather than waiting for your next scheduled check.