Prediabetes rarely produces obvious symptoms. That’s the most important thing to know: 8 in 10 adults who have it don’t know they have it, according to the CDC. Your blood sugar is running higher than normal but not yet high enough to qualify as type 2 diabetes, and at that level, your body doesn’t send the kind of alarm signals most people expect. Still, there are subtle physical changes, risk factors, and lab markers worth understanding, because without intervention, many people with prediabetes develop type 2 diabetes within five years.
Why Prediabetes Is Usually Silent
The classic diabetes warning signs, like intense thirst, frequent urination, blurred vision, and tingling in your hands or feet, generally don’t show up until blood sugar has climbed into the diabetic range. That’s because your body can still compensate during prediabetes. Your pancreas works harder, pumping out extra insulin to force glucose into cells that have become less responsive. For a while, this brute-force approach keeps blood sugar from spiking dramatically, which means you feel more or less fine even as damage quietly accumulates.
What’s actually happening under the surface is insulin resistance: cells in your muscles, fat tissue, and liver stop responding well to insulin. Glucose builds up in your blood instead of entering cells for energy. Eventually the pancreas can’t keep up, and blood sugar rises further. But during the prediabetic window, the rise is gradual enough that most people notice nothing at all.
Physical Signs That Can Appear
One visible change linked to prediabetes is darkened, velvety patches of skin, a condition called acanthosis nigricans. These patches are typically brown or black and show up in skin folds: the back of the neck, armpits, groin, and under the breasts. The skin may feel thicker than normal, and small skin tags sometimes develop in the same areas. This happens because elevated insulin levels stimulate skin cell growth. If you’ve noticed these patches and can’t explain them, it’s worth getting your blood sugar checked.
Some people also report persistent fatigue or low energy, which makes sense physiologically. When your cells resist insulin, they’re less efficient at pulling glucose from your blood to use as fuel. The result can be a vague, ongoing tiredness that doesn’t improve much with sleep. This symptom is easy to dismiss or blame on stress, which is part of why prediabetes goes undetected so often.
Damage Starts Before Diabetes
One reason prediabetes matters, even without symptoms, is that it’s not a harmless waiting room. Research published in the American Heart Association’s journal Circulation found that people with prediabetes already show measurable dysfunction in their smallest blood vessels, the ones that supply the eyes, skin, kidneys, and nerves. The decline in microvascular function during prediabetes was roughly one quarter to one half as severe as in people with full type 2 diabetes.
This supports what researchers call the “ticking clock hypothesis”: the cardiovascular damage associated with diabetes doesn’t start at diagnosis. It starts years earlier, during prediabetes, when arteries begin to stiffen and blood vessel linings stop working as well. That’s why catching prediabetes early has value beyond simply preventing diabetes. It’s a chance to slow or stop vascular damage that contributes to heart disease, kidney problems, and cognitive decline.
Who Should Get Screened
Because symptoms are unreliable, screening is the only way most people find out. The U.S. Preventive Services Task Force recommends that adults aged 35 to 70 who are overweight or obese get screened for prediabetes. For Asian Americans, screening is recommended at a lower BMI threshold of 23 or above, because the risk starts earlier at lower body weights. For Black, Hispanic/Latino, American Indian/Alaska Native, and Native Hawaiian/Pacific Islander adults, screening may be appropriate before age 35 due to higher population-level diabetes rates.
Certain life events also raise your risk substantially. Women who had gestational diabetes during pregnancy, or who delivered a baby weighing more than 9 pounds, face a significantly higher chance of developing prediabetes later. Polycystic ovary syndrome (PCOS) is another major risk factor: more than half of women with PCOS develop type 2 diabetes before age 40, often passing through prediabetes first. A family history of type 2 diabetes, a sedentary lifestyle, and carrying excess weight around the midsection all add to the risk.
How Prediabetes Is Diagnosed
Three blood tests can identify prediabetes, and your doctor may use any one of them. The most common is the A1C test, which reflects your average blood sugar over the past two to three months. An A1C between 5.7% and 6.4% falls in the prediabetic range. A fasting blood sugar test measures glucose after you haven’t eaten for at least eight hours; a result between 100 and 125 mg/dL indicates prediabetes. The third option is an oral glucose tolerance test, where you drink a sugary solution and have your blood sugar measured two hours later; a reading between 140 and 199 mg/dL signals prediabetes.
Any result at or above these ranges moves into diabetic territory. Any result below them is considered normal, though levels near the upper edge of “normal” still warrant attention and lifestyle monitoring.
Reversing Prediabetes With Lifestyle Changes
Prediabetes is one of the few conditions where the word “reversible” genuinely applies. The landmark Diabetes Prevention Program study established that modest weight loss, just 5% to 7% of body weight, combined with 150 minutes of physical activity per week dramatically cuts the risk of progressing to type 2 diabetes. For someone weighing 200 pounds, that’s a loss of 10 to 14 pounds. The exercise doesn’t need to be intense; brisk walking counts.
Participants in structured prevention programs who hit at least 150 minutes of weekly activity had a 50% success rate in reaching the 5% weight loss goal. And the data showed a steep relationship between activity and results: going above 150 minutes per week was associated with substantially higher success rates. These aren’t extreme changes. They’re the kind of adjustments, eating smaller portions, swapping processed carbs for whole grains and vegetables, walking after meals, that are sustainable over years.
The payoff goes beyond blood sugar numbers. Because vascular damage is already underway during prediabetes, the cardiovascular benefits of losing weight and moving more start immediately. You’re not just preventing a future diagnosis. You’re protecting blood vessels, kidneys, and nerves that are already under strain.