Most people with prediabetes have no obvious symptoms, which is exactly why 8 in 10 adults who have it don’t know. The condition is defined by blood sugar levels that are higher than normal but not yet high enough to qualify as type 2 diabetes. For most people, the only reliable way to know is a blood test, but there are risk factors and subtle physical signs that can tell you whether screening makes sense.
Why Prediabetes Rarely Feels Like Anything
Prediabetes develops gradually over years. What’s happening inside your body is a slow breakdown in how you process sugar. Normally, insulin moves sugar from your blood into your cells for energy. When your cells start ignoring insulin’s signal (a process called insulin resistance), your pancreas compensates by pumping out more insulin to keep blood sugar in check. For a while, this works. You feel fine because your blood sugar stays relatively normal, even though your pancreas is working overtime.
The trouble starts when your insulin-producing cells can’t keep up with the demand. They begin to wear out, and blood sugar creeps higher. This is the prediabetic phase. Because the rise is gradual, your body adapts, and you don’t feel the shift. That’s why waiting for symptoms is not a useful strategy.
Skin Changes That Signal Insulin Resistance
One physical sign worth knowing about is acanthosis nigricans: patches of dark, thick, velvety skin that develop in body folds and creases, most commonly the back of the neck, armpits, and groin. The affected skin may also be itchy or develop small skin tags. These changes develop slowly, so you might not notice them right away.
Acanthosis nigricans is strongly linked to insulin resistance. People who have it are much more likely to develop type 2 diabetes. It’s not a diagnosis on its own, but if you notice darkened, thickened skin in those areas, it’s a meaningful reason to get your blood sugar tested.
Risk Factors That Should Prompt Screening
The CDC’s prediabetes risk assessment scores you on seven factors: age, sex, history of gestational diabetes, family history of diabetes, high blood pressure, physical activity level, and weight. Each one adds points, and the more you accumulate, the higher your risk. Here’s what increases your score:
- Age over 40. Risk climbs with each decade, with the highest points assigned at 60 and older.
- Being male. Men carry slightly higher statistical risk at any given weight.
- Gestational diabetes. Women who had high blood sugar during pregnancy remain at elevated risk years later.
- A parent or sibling with diabetes. Family history is one of the strongest predictors.
- High blood pressure. Hypertension and insulin resistance frequently travel together.
- Sedentary lifestyle. Regular physical activity improves how your cells respond to insulin.
- Higher body weight. Excess weight, especially around the midsection, is the single largest modifiable risk factor.
Ethnicity also matters. If you’re Black, Hispanic or Latino, American Indian, Alaska Native, Asian American, or Pacific Islander, your risk is disproportionately higher. Asian Americans in particular face increased risk at lower body weights, roughly 15 pounds below the thresholds that apply to other groups.
When to Get Tested
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 (a BMI of 25 or higher). If you’re Asian American, the threshold drops to a BMI of 23. And if you belong to a population with higher diabetes prevalence, screening at a younger age is reasonable even without other risk factors.
These recommendations apply to people who feel perfectly healthy. You don’t need symptoms to justify asking your doctor for a blood sugar check. If you have multiple risk factors, screening earlier than 35 is appropriate.
The Three Blood Tests That Diagnose Prediabetes
Doctors use three tests, and any one of them can identify prediabetes. The most common is the A1C test, which measures your average blood sugar over the past two to three months. An A1C between 5.7% and 6.4% falls in the prediabetes range. Below 5.7% is normal; 6.5% or higher is diabetes.
The second option is a fasting plasma glucose test, taken after you haven’t eaten for at least eight hours. A result between 100 and 125 mg/dL indicates prediabetes. The third 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 puts you in prediabetic territory.
Your doctor may use one or a combination. The A1C is convenient because it doesn’t require fasting and reflects a longer window of blood sugar behavior rather than a single snapshot.
Damage Can Start Before a Diabetes Diagnosis
One of the most important things to understand about prediabetes is that it’s not a “pre” problem. The body doesn’t wait for a diabetes diagnosis before damage begins. Research shows that microvascular complications, the kind of small blood vessel damage associated with diabetes, can develop while blood sugar is still in the prediabetic range.
Retinopathy, or damage to the blood vessels in the eyes, occurs in an estimated 8% to 12% of people with prediabetes. Changes in nerve function show up in 18% to 25% of prediabetic patients, particularly affecting the small nerve fibers that carry pain and temperature signals and regulate functions like heart rate and digestion. Early kidney damage, detected through protein in the urine, also appears at higher rates in people with elevated but sub-diabetic blood sugar.
These numbers challenge the common assumption that prediabetes is a warning with no real consequences yet. The window between “normal” and “diabetic” is not a safe zone. It’s a period when prevention matters most, precisely because the body is already accumulating harm.
What Happens Inside Your Body During Prediabetes
Excess body fat, particularly the type stored around organs, makes your cells less responsive to insulin. When circulating levels of saturated fatty acids are high (from diet or from fat stores breaking down), those fats compete with glucose for entry into your cells. The result is a traffic jam: sugar builds up in your blood while your tissues struggle to use it efficiently.
Your pancreas responds by producing more and more insulin. For a time, this compensatory phase keeps things in balance. But the insulin-producing cells have a ceiling. Once they’re working at maximum capacity, any further rise in blood sugar can’t trigger more output. Fat deposits within the pancreas itself can worsen the problem, creating a toxic local environment that accelerates the decline. The progression from compensating pancreas to exhausted pancreas is the bridge between prediabetes and type 2 diabetes.
How Likely Is Progression to Type 2 Diabetes
Not everyone with prediabetes develops diabetes. In a large study tracking progression over time, the 10-year risk for a 45-year-old with prediabetes ranged from about 9% to 25%, depending on how prediabetes was defined and measured. That means the majority of people at any given point will not progress within a decade, but a significant minority will.
The factors that push someone toward progression are the same ones that caused prediabetes in the first place: continued weight gain, inactivity, and worsening insulin resistance. Landmark research has shown that modest weight loss (5% to 7% of body weight) and 150 minutes of moderate physical activity per week can cut the risk of progression by more than half. These aren’t extreme changes. For someone weighing 200 pounds, that’s 10 to 14 pounds. For exercise, it works out to about 30 minutes of brisk walking five days a week.
Prediabetes is reversible in many cases. Blood sugar levels can return to the normal range with sustained lifestyle changes, and the earlier you catch it, the more effective those changes tend to be.