Most people with prediabetes have no symptoms at all, which is exactly why it’s so easy to miss. About 25% of people with prediabetes will develop type 2 diabetes within three to five years, but a blood test is the only reliable way to catch it early. The good news: once you know, straightforward lifestyle changes can cut that risk dramatically.
Why Prediabetes Rarely Has Symptoms
Prediabetes is what happens when your blood sugar is higher than normal but not yet high enough to qualify as type 2 diabetes. Your body still produces insulin, the hormone that moves sugar from your blood into your cells. But over time, your cells start responding less effectively to that insulin. The pancreas compensates by producing more, which works for a while. During this phase, most people feel completely fine.
Because this process unfolds gradually over months or years, there’s no clear moment when you’d feel something change. That’s what makes screening so important. By the time symptoms like increased thirst, frequent urination, or blurred vision show up, blood sugar levels have often crossed into the diabetes range.
Physical Signs That Can Point to Insulin Resistance
While prediabetes itself is largely silent, insulin resistance (the underlying driver) can leave visible clues on your skin. The most recognizable is a condition called acanthosis nigricans: patches of darkened, velvety skin that typically appear on the neck, armpits, groin, or under the breasts. These patches may also itch or have a noticeable odor. Skin tags in these same areas are another common sign.
These skin changes don’t confirm prediabetes on their own, but they’re a strong signal that your insulin levels are running higher than they should be. If you notice them, it’s worth getting your blood sugar checked.
The Three Blood Tests Used for Diagnosis
A prediabetes diagnosis comes from one of three standard blood tests. You only need one abnormal result to qualify.
- A1C test: Measures your average blood sugar over the past two to three months. A result between 5.7% and 6.4% indicates prediabetes. This test doesn’t require fasting, which makes it the most convenient option.
- Fasting blood sugar: Taken after at least eight hours without eating. A result between 100 and 125 mg/dL falls in the prediabetes range.
- Oral glucose tolerance test: You drink a sugary solution, then have your blood drawn two hours later. A result between 140 and 199 mg/dL signals prediabetes.
Your doctor will typically start with an A1C or fasting blood sugar test since these are simpler. If results are borderline or inconsistent, they may follow up with one of the other tests to confirm.
When A1C Results Can Be Misleading
The A1C test works by measuring how much sugar has attached to your hemoglobin, the protein in red blood cells that carries oxygen. But certain hemoglobin variants can throw off that measurement, producing results that are falsely high or falsely low. These variants are more common in people with ancestry from Africa, South and Southeast Asia, the Mediterranean, and the Caribbean.
Conditions that affect red blood cells, like anemia or certain blood disorders, can also skew A1C results. If your A1C doesn’t match a fasting blood sugar test, or if your results seem inconsistent with previous testing, your doctor may switch to a glucose-based test instead. This is especially worth flagging if you have a family history of blood disorders or if your ancestors came from regions where hemoglobin variants are common.
Who Should Get Screened
The U.S. Preventive Services Task Force recommends screening for prediabetes in adults aged 35 to 70 who are overweight or obese (a BMI of 25 or higher). That starting age was recently lowered from 40 to 35, reflecting growing evidence that earlier detection matters.
Screening should start even younger if you belong to a population with higher diabetes rates, including American Indian/Alaska Native, Black, Hispanic/Latino, or Native Hawaiian/Pacific Islander communities. For Asian Americans, the BMI threshold drops to 23, since metabolic risk increases at a lower weight in this group.
Factors That Raise Your Risk
The CDC’s prediabetes risk assessment captures the major factors that increase your likelihood of developing the condition. Some are within your control, others aren’t, but knowing where you stand helps you decide whether to get tested.
- Family history: Having a parent or sibling with diabetes significantly raises your risk.
- Weight: A higher BMI is one of the strongest predictors.
- Physical inactivity: Regular movement improves how your body uses insulin. Being sedentary does the opposite.
- Age: Risk increases as you get older, particularly after 35.
- High blood pressure: This often travels alongside insulin resistance as part of a cluster of metabolic problems.
- Gestational diabetes: If you developed diabetes during pregnancy, your long-term risk of type 2 diabetes is elevated even after delivery.
- Race and ethnicity: Certain groups face disproportionately higher rates, likely due to a combination of genetic, environmental, and systemic factors.
The CDC offers a free online risk test that takes about a minute. It won’t replace a blood test, but a high score is a solid reason to schedule one.
What Happens If You Don’t Address It
Prediabetes is not a guarantee that diabetes is coming, but it’s not a neutral finding either. Roughly one in four people with prediabetes will progress to type 2 diabetes within three to five years. The progression isn’t random. It follows a feedback loop: elevated blood sugar forces the pancreas to release more insulin, the body’s insulin receptors become less responsive over time, and blood sugar climbs further. Without intervention, this cycle accelerates.
Beyond diabetes itself, prediabetes is associated with increased cardiovascular risk. The same metabolic dysfunction that raises blood sugar also contributes to high blood pressure, abnormal cholesterol levels, and inflammation in blood vessels.
How Lifestyle Changes Lower the Risk
The most encouraging data on prediabetes comes from the landmark Diabetes Prevention Program study. Participants who lost 5% to 7% of their body weight (10 to 14 pounds for someone weighing 200 pounds) and stayed physically active reduced their risk of developing type 2 diabetes by 58%. That’s a larger effect than what medication achieved in the same study.
The changes that drove those results weren’t extreme. Participants aimed for 150 minutes of moderate activity per week, roughly 30 minutes a day for five days. Walking counts. The weight loss target was modest by design, because even small reductions in body fat improve how your cells respond to insulin.
The CDC’s National Diabetes Prevention Program offers year-long structured programs based on this research. These are available in person and online, often covered by insurance, and led by trained lifestyle coaches. The program focuses on practical skills: meal planning, managing stress, building sustainable habits rather than short-term diets.
If blood tests confirm prediabetes, the most useful thing you can do is treat it as a warning you caught early rather than a diagnosis you’re stuck with. The window between prediabetes and diabetes is where intervention works best, and in many cases, blood sugar levels can return to normal range entirely.