Most people with prediabetes have no obvious symptoms, which is exactly why 8 in 10 of the 115 million American adults with the condition don’t know they have it. The only reliable way to confirm prediabetes is a blood test, but certain physical signs, risk factors, and a simple at-home screening can tell you whether it’s time to get one.
Prediabetes Rarely Causes Noticeable Symptoms
Unlike full-blown diabetes, prediabetes doesn’t typically make you feel sick. You probably won’t notice increased thirst, frequent urination, or fatigue at this stage. Blood sugar levels are elevated enough to cause internal damage but not high enough to produce the classic warning signs most people associate with diabetes.
There is one visible clue worth checking for: patches of dark, thick, velvety skin in body folds and creases, most commonly the back of the neck, armpits, and groin. This condition, called acanthosis nigricans, develops slowly and is strongly linked to insulin resistance, the underlying problem that drives prediabetes. The affected skin may feel itchy, develop small skin tags, or have a slight odor. If you notice these patches, it’s a strong signal your body is struggling to process insulin properly.
Risk Factors That Should Prompt Testing
Because symptoms are so unreliable, your personal risk profile matters more. The CDC’s prediabetes risk test scores seven factors, and the more that apply to you, the more urgently you should get blood work done:
- Age: Risk climbs with each decade, particularly after 40.
- Weight: Carrying extra weight, especially around the midsection, is the single biggest modifiable risk factor. A waist measurement over 35 inches for women or over 40 inches for men signals higher risk.
- Family history: Having a parent or sibling with type 2 diabetes increases your odds significantly.
- High blood pressure: A current or past diagnosis adds to your risk.
- Physical inactivity: A sedentary lifestyle independently raises your chances.
- Gestational diabetes: Women who had diabetes during pregnancy remain at elevated risk years later.
The U.S. Preventive Services Task Force recommends routine screening for adults aged 35 to 70 who are overweight or obese. If you’re Asian American, screening is recommended at a lower BMI threshold (23 instead of 25) because metabolic complications can develop at lower body weights. Black, Hispanic/Latino, American Indian/Alaska Native, and Native Hawaiian/Pacific Islander adults should also consider screening before age 35, since these populations face disproportionately high diabetes rates.
The Three Blood Tests That Confirm Prediabetes
Your doctor can use any of three tests. Each measures blood sugar differently, and any one of them is enough for a diagnosis.
A1C Test
This is the most convenient option because it doesn’t require fasting. It measures your average blood sugar over the previous two to three months. A result between 5.7% and 6.4% means prediabetes. Below 5.7% is normal, and 6.5% or higher indicates diabetes.
Fasting Blood Glucose
You fast overnight for at least eight hours, then have blood drawn. A reading between 100 and 125 mg/dL falls in the prediabetes range. Below 100 is normal, and 126 or above points to diabetes. This test captures how well your body manages blood sugar at rest, without any food influence.
Oral Glucose Tolerance Test
This one takes more time. You fast overnight, have your blood drawn, drink a sugary solution, and then have blood drawn again two hours later. A two-hour result between 140 and 199 mg/dL indicates prediabetes. This test reveals how efficiently your body clears sugar after a meal, which can catch problems the fasting test sometimes misses. Some people have normal fasting levels but struggle to process sugar after eating, and this test picks that up.
It’s possible to have a normal result on one test and a prediabetic result on another. If your doctor suspects prediabetes, they may run more than one to get the clearest picture.
What a Prediabetes Diagnosis Actually Means
Prediabetes isn’t a guarantee that you’ll develop type 2 diabetes, but the odds aren’t small. Without intervention, roughly 5% to 10% of people with prediabetes progress to full diabetes each year, and about 70% will eventually develop it over their lifetime. Those numbers make it clear that prediabetes is a serious warning, not a vague suggestion that something might go wrong someday.
The encouraging part is that this stage is reversible. Your blood sugar is elevated but hasn’t crossed the line into permanent metabolic dysfunction. Losing 5% to 7% of your body weight (about 10 to 14 pounds for someone who weighs 200) and getting 150 minutes of moderate physical activity per week, roughly 30 minutes five days a week, has been shown to cut the risk of progressing to diabetes by more than half.
How to Check Your Risk Right Now
The CDC offers a free one-minute risk test you can take online at cdc.gov/prediabetes. It scores you on the seven factors listed above: age, sex, gestational diabetes history, family history, blood pressure, physical activity, and weight category. A score of 5 or higher means your risk is elevated enough to warrant a blood test. The quiz doesn’t diagnose anything, but it takes the guesswork out of deciding whether lab work is worth pursuing. Given that 2 in 5 American adults already have prediabetes and the vast majority don’t know it, taking 60 seconds to check is a reasonable first step.