Prediabetes is a condition where your blood sugar levels are higher than normal but not yet high enough to qualify as type 2 diabetes. More than 115 million American adults have it, and 8 in 10 of them don’t know. That’s because prediabetes rarely causes noticeable symptoms, making blood tests the only reliable way to catch it.
What Happens in Your Body
Your body uses a hormone called insulin to move sugar from your bloodstream into your cells, where it’s used for energy. In prediabetes, your cells stop responding to insulin as well as they should. Your muscles, fat, and liver essentially start ignoring insulin’s signal to absorb sugar. Your pancreas compensates by producing more insulin, but over time it can’t keep up. The result is sugar building up in your blood at levels that are abnormal but haven’t crossed into diabetes territory.
This process doesn’t happen overnight. It develops gradually over years, which is why prediabetes sits in a gray zone between healthy blood sugar and full diabetes.
How Prediabetes Is Diagnosed
Three standard blood tests can identify prediabetes, and only one needs to come back abnormal for a diagnosis:
- A1C test: Measures your average blood sugar over the past two to three months. A result between 5.7% and 6.4% indicates prediabetes. Below 5.7% is normal, and 6.5% or higher means diabetes.
- Fasting blood sugar: Taken after you haven’t eaten for at least eight hours. A reading of 100 to 125 mg/dL falls in the prediabetes range. Normal is under 100, and 126 or above is diabetes.
- Oral glucose tolerance test: You drink a sugary solution, and your blood sugar is checked two hours later. A result between 140 and 199 mg/dL signals prediabetes.
Risk doesn’t jump suddenly at these cutoffs. It rises continuously, getting disproportionately higher as your numbers climb toward the upper end of each range. Someone at 6.3% A1C carries more risk than someone at 5.8%, even though both technically have prediabetes.
Who Should Get Screened
The U.S. Preventive Services Task Force recommends screening for adults aged 35 to 70 who are overweight or obese. Being overweight is the single strongest risk factor. Other factors that increase your chances include a family history of diabetes, a history of gestational diabetes during pregnancy, polycystic ovarian syndrome, and older age.
If you’re Asian American, screening is recommended at a lower BMI (23 and above instead of the usual 25) because diabetes risk rises at lower body weights in this population. Earlier screening is also recommended for Black, Hispanic/Latino, American Indian/Alaska Native, and Native Hawaiian/Pacific Islander adults, who develop diabetes at higher rates overall.
Symptoms Are Rare, but Not Nonexistent
Prediabetes typically causes no symptoms at all. That’s what makes it so easy to miss. However, one visible sign that sometimes appears is darkened, velvety patches of skin on the neck, armpits, or groin. This condition, called acanthosis nigricans, happens when elevated insulin levels stimulate skin cell growth. Small skin tags in these areas can also be a clue.
If you start noticing increased thirst, frequent urination, fatigue, or blurred vision, those are signs your blood sugar may have already crossed from prediabetes into type 2 diabetes.
The Risk of Doing Nothing
Without changes, roughly 2% of people with prediabetes progress to type 2 diabetes each year. Over five years, about 9% of people with A1C-defined prediabetes make that transition. Those numbers may sound modest, but the risk compounds over time, and prediabetes itself isn’t harmless while you wait.
Even before reaching diabetes, elevated blood sugar takes a toll on your cardiovascular system. A large meta-analysis published in The BMJ found that people with prediabetes had a 16% higher risk of coronary heart disease and a 14% higher risk of stroke compared to people with normal blood sugar, over roughly a decade of follow-up. Your heart and blood vessels don’t wait for a diabetes diagnosis to start accumulating damage.
Prediabetes Can Be Reversed
The most encouraging thing about prediabetes is that it responds well to lifestyle changes. The landmark Diabetes Prevention Program study found that losing 5% to 7% of body weight (10 to 14 pounds for a 200-pound person) reduced the risk of developing type 2 diabetes by 58%. Participants achieved this through a combination of healthier eating and about 150 minutes of moderate physical activity per week, roughly 30 minutes on most days.
That 58% reduction is larger than what most medications can offer. The changes don’t need to be dramatic. Walking counts. So does swapping refined carbohydrates for whole grains, eating more vegetables, and reducing portion sizes. The CDC runs a National Diabetes Prevention Program with structured year-long courses designed around these principles, available in person and online across the country.
When Medication Enters the Picture
For some people, lifestyle changes alone aren’t enough or aren’t realistic. Metformin, a widely used and inexpensive medication, can help lower blood sugar in the prediabetes stage. Clinical trials found it was most effective for adults under 60, those with a BMI over 35, and women who had gestational diabetes. It’s not typically a first-line approach for everyone with prediabetes, but it’s an option worth discussing if you fall into a higher-risk group or haven’t seen results from lifestyle changes alone.
What Prediabetes Means for You Practically
A prediabetes diagnosis is not a diabetes diagnosis. It’s a warning that your metabolism is heading in a direction you want to correct. Many people bring their blood sugar back into the normal range and stay there. The key is knowing you have it in the first place, which is why screening matters so much given that the vast majority of people with prediabetes are unaware.
If you’ve been told your blood sugar is “a little high” or “borderline,” that likely means prediabetes. Ask for your specific numbers. Knowing whether your A1C is 5.8% or 6.3% gives you a clearer picture of how much ground you need to cover and how urgently. Then focus on the changes with the biggest proven payoff: modest weight loss and regular physical activity.