Insulin resistance is extremely common. In the United States, roughly 38% of nondiabetic adults have it, based on national survey data from 2017–2018. That’s up from about 25% two decades earlier, meaning the prevalence has increased by more than half in just 20 years. When you include people who already have type 2 diabetes (which insulin resistance nearly always precedes), the total number of affected Americans is even higher.
How Prevalence Has Changed Over Time
National health survey data tracking U.S. adults from 1999 to 2018 shows a steady climb. The age-adjusted prevalence of insulin resistance rose from 24.8% in 1999–2000 to 38.4% in 2017–2018. High insulin levels, a closely related marker, climbed from 28.2% to 41.4% over the same period. These figures exclude people already diagnosed with diabetes, so they reflect otherwise “healthy” adults whose bodies are quietly struggling to process blood sugar normally.
The increase tracks with rising rates of obesity, sedentary lifestyles, and diets high in processed carbohydrates and added sugars. But insulin resistance isn’t limited to people who are visibly overweight. It can develop in people with a normal BMI, particularly if they carry excess fat around the midsection.
Who Is Most Affected
Certain groups consistently show higher rates. Men have a higher prevalence than women across nearly all age groups. Hispanic and non-Hispanic Black adults are more affected than non-Hispanic white adults. Lower income and lower educational attainment also correlate with higher rates, likely reflecting differences in access to fresh food, safe places to exercise, and preventive healthcare.
Age is another major factor. Your cells naturally become less responsive to insulin as you get older, which is why the condition becomes more common after 40 and especially after 60. But increasingly, insulin resistance is showing up in adolescents and young adults, driven by rising childhood obesity rates.
Insulin Resistance in Women With PCOS
Polycystic ovary syndrome is one of the conditions most tightly linked to insulin resistance. In a study of 271 women with PCOS, 64% were insulin resistant after adjusting for other factors. That’s dramatically higher than the general female population. The relationship runs both directions: insulin resistance worsens the hormonal imbalances behind PCOS, and the hormonal disruption of PCOS can further impair insulin sensitivity. For many women, irregular periods, difficulty losing weight, or fertility struggles are what ultimately lead to the discovery of underlying insulin resistance.
How It Differs From Prediabetes
Insulin resistance and prediabetes are related but not the same thing. Insulin resistance is the underlying mechanism: your muscle, fat, and liver cells stop responding well to insulin, forcing your pancreas to produce more of it to keep blood sugar in check. As long as your pancreas can compensate, your blood sugar stays normal. You’re insulin resistant, but you don’t yet have prediabetes.
Prediabetes develops when your pancreas can no longer keep up. Blood sugar starts creeping above normal, though not high enough for a diabetes diagnosis. This means you can be insulin resistant for years before it ever shows up on a standard blood sugar test. The National Institute of Diabetes and Digestive and Kidney Diseases notes that healthcare professionals don’t routinely test for insulin resistance itself, since the most accurate test is mainly used in research settings. Prediabetes, by contrast, is diagnosed with common blood tests like fasting glucose or hemoglobin A1C.
This gap matters because it means many people with insulin resistance don’t know they have it. Their fasting glucose looks fine, so nothing gets flagged. The condition can quietly progress for a decade or more before blood sugar numbers cross into the prediabetes or diabetes range.
Signs Your Body May Show
Because insulin resistance doesn’t cause obvious symptoms early on, physical signs can be easy to miss or dismiss. One of the more visible markers is a darkened, velvety patch of skin, typically on the neck, armpits, or groin. This skin change, called acanthosis nigricans, is strongly correlated with high insulin levels. A study of over 1,400 children found it in 7.1% of the group overall, but rates varied sharply by ethnicity: it appeared in roughly 13% of Black children and about 6% of Hispanic children, while being rare in white non-Hispanic children. The severity of the darkening tracks closely with how elevated someone’s fasting insulin is.
Other common patterns include persistent difficulty losing weight (especially around the belly), fatigue after meals, strong sugar cravings, and skin tags. None of these are definitive on their own, but a cluster of them in someone with risk factors is worth investigating.
How It’s Detected
Standard checkups typically measure fasting blood glucose and sometimes A1C, but these only catch the problem once blood sugar has already started rising. A fasting insulin test can reveal the condition earlier. In a healthy person with normal insulin sensitivity, fasting insulin should stay below 25 mIU/L alongside normal blood sugar levels. Levels above that suggest your pancreas is working overtime to compensate for resistant cells.
Some clinicians use a calculation called HOMA-IR, which combines your fasting insulin and fasting glucose into a single score. While cutoff values vary by population, a HOMA-IR above roughly 2.5 to 2.8 is generally considered a sign of insulin resistance. If you’re concerned, asking your doctor for a fasting insulin test alongside your regular glucose check gives a much more complete picture of your metabolic health than glucose alone.
Why the Numbers Keep Climbing
The sharp rise in prevalence over the past two decades isn’t genetic. Human biology hasn’t changed in 20 years. What has changed is the food environment, activity levels, sleep patterns, and chronic stress loads that most people live with. Ultra-processed foods now make up the majority of calories in the average American diet, and these foods tend to spike blood sugar and insulin repeatedly throughout the day. Sedentary work has become the norm. Sleep deprivation, which independently worsens insulin sensitivity, is widespread.
The practical takeaway is that insulin resistance is no longer a niche metabolic condition. It affects more than one in three American adults who don’t even have diabetes yet, it’s getting more common every year, and it often goes undetected until it has already progressed to prediabetes or worse. The same lifestyle factors that drive it, particularly diet, physical activity, and body composition, are also the most effective tools for reversing it, often without medication.