Prediabetes rarely announces itself with obvious symptoms. Over 115 million American adults have it, and 8 in 10 of them don’t know. The only reliable way to confirm prediabetes is a blood test, but there are risk factors, subtle body changes, and screening guidelines that can tell you whether it’s time to get one.
Why Prediabetes Is Easy to Miss
Prediabetes doesn’t usually cause signs or symptoms you’d notice day to day. Unlike full type 2 diabetes, which can trigger obvious thirst, frequent urination, fatigue, and blurred vision, the prediabetic stage is mostly silent. Your blood sugar is elevated above normal but not yet high enough to produce those classic warning signals.
What’s happening inside your body, though, is significant. Your cells are becoming less responsive to insulin, the hormone that moves sugar from your blood into your cells for energy. To compensate, your pancreas works harder, pumping out more insulin to keep blood sugar in check. This can go on for years. But over time, the insulin-producing cells in your pancreas become overworked and start to burn out, losing the ability to keep up with demand. That tipping point is when blood sugar climbs from prediabetic into diabetic range. Up to 70% of people with prediabetes eventually develop type 2 diabetes if nothing changes.
Physical Signs Worth Checking
One visible clue is darkened, velvety patches of skin, a condition called acanthosis nigricans. These patches typically appear on the back of the neck, in the armpits, or in the groin. The skin may also feel thicker than surrounding areas. This discoloration is directly linked to insulin resistance and is one of the few things you can spot in a mirror.
Skin tags in the same areas, particularly the neck and armpits, are another physical marker. On their own, skin tags are common and harmless. But clusters of skin tags alongside darkened skin patches can point to an underlying metabolic problem worth investigating.
If you’ve started noticing increased thirst, more frequent trips to the bathroom, unexplained fatigue, or tingling in your hands or feet, those symptoms suggest your blood sugar may have already crossed from prediabetes into type 2 diabetes territory.
Risk Factors That Should Prompt Testing
The U.S. Preventive Services Task Force recommends screening for prediabetes in adults aged 35 to 70 who are overweight (BMI of 25 or higher) or obese. If you’re Asian American, the threshold is lower: a BMI of 23 or above. And if you’re American Indian, Alaska Native, Black, Hispanic or Latino, or Native Hawaiian or Pacific Islander, screening at a younger age is appropriate because these populations face disproportionately higher diabetes rates.
Beyond BMI, waist circumference is a useful at-home check. Carrying excess fat around your midsection is a stronger predictor of insulin resistance than overall body weight. The thresholds to watch: less than 31.5 inches (80 cm) for women, less than 37 inches (94 cm) for most men, and less than 35 inches (90 cm) for South Asian men. Measuring above these numbers increases your metabolic risk.
Other factors that raise your likelihood include a family history of type 2 diabetes, a history of gestational diabetes, polycystic ovary syndrome, physical inactivity, and age over 45.
The Three Blood Tests That Diagnose Prediabetes
Any of three standard blood tests can identify prediabetes. Your doctor will typically choose one based on convenience and your individual situation.
- 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 and can be done at any time of day, making it the most convenient option.
- Fasting blood glucose: Taken after at least eight hours without eating. A result between 100 and 125 mg/dL falls in the prediabetic range.
- Oral glucose tolerance test: You drink a sugary solution, then have your blood drawn two hours later. A reading between 140 and 199 mg/dL signals prediabetes.
Numbers below those ranges are normal. Numbers above them indicate type 2 diabetes. If your result lands in the prediabetic zone, your doctor will typically retest to confirm.
Damage Can Start Before a Diabetes Diagnosis
One of the most important things to understand about prediabetes is that it isn’t a harmless waiting room before “real” diabetes. Blood sugar levels between normal and diabetic can already begin affecting small blood vessels and nerves throughout your body.
Between 11% and 25% of people with prediabetes already have peripheral neuropathy, which shows up as numbness, tingling, or pain in the feet and hands. An estimated 13% to 21% experience neuropathic pain specifically. The small nerve fibers that carry pain and temperature signals and regulate things like heart rate and digestion are among the first affected. Retinal damage, the kind that can eventually threaten vision, occurs in an estimated 8% to 12% of people with prediabetes. Early kidney changes have also been documented at prediabetic glucose levels.
None of this means damage is inevitable, but it does mean prediabetes deserves to be treated seriously rather than brushed off as “borderline.”
Prediabetes Is Reversible
The most encouraging fact about prediabetes is that it responds well to lifestyle changes. The landmark Diabetes Prevention Program study found that losing just 5% to 7% of body weight, roughly 10 to 14 pounds for someone weighing 200 pounds, reduced the risk of progressing to type 2 diabetes by 58%. That reduction came from a combination of modest weight loss and about 150 minutes of moderate physical activity per week, like brisk walking for 30 minutes five days a week.
The CDC’s National Diabetes Prevention Program offers structured, year-long programs based on this research, available in person and online across the country. Participants work with a lifestyle coach to make gradual changes to eating, activity, and stress management. The focus is on sustainable habits rather than aggressive dieting.
For many people, these changes are enough to bring blood sugar back into a normal range. The key is catching prediabetes early enough to act on it, which circles back to the core challenge: you have to test for it, because your body probably won’t tell you on its own.