Kidney stones affect roughly 1 in 11 American adults, making them one of the most common urinary tract conditions. Based on national survey data covering nearly 38,000 adults, about 9.25% of the U.S. population has had at least one kidney stone. That number has been climbing for decades, driven by rising obesity rates, dietary shifts, and even warming temperatures.
Overall Prevalence in the U.S.
The 9.25% figure comes from the most recent analysis of the National Health and Nutrition Examination Survey, which tracks health conditions across a representative sample of American adults. That translates to tens of millions of people who have experienced a stone at some point in their lives. Globally, an estimated 106 million new cases were recorded in 2021 alone, with more than two-thirds occurring in men.
These numbers likely undercount the true burden, since small stones can pass without symptoms and never get diagnosed. People who have had one stone face particularly steep odds of getting another: recurrence rates reach as high as 50% within five years and 80 to 90% within ten years. For many people, kidney stones aren’t a one-time event but a recurring condition that requires long-term dietary and medical management.
Who Gets Kidney Stones Most Often
Men develop kidney stones at roughly twice the rate of women, though that gap has been narrowing over the past few decades. Women’s rates have risen faster than men’s, possibly due to increasing rates of obesity and metabolic conditions that raise stone risk across both sexes.
Most first-time stones appear between ages 30 and 60, with risk climbing through middle age. But kidney stones aren’t limited to adults. After a period of declining rates, pediatric kidney stone diagnoses started climbing globally around 2015 and have continued trending upward since. A South Carolina study tracking over 4.6 million people found that children had double the risk of developing stones compared to earlier estimates, a shift many researchers attribute to changes in childhood diet and hydration habits.
Geography Plays a Surprising Role
Where you live meaningfully affects your risk. The southeastern United States is known as the “Stone Belt” because residents there are about 50% more likely to develop kidney stones than people living in other parts of the country. Heat and humidity increase fluid loss through sweat, concentrating the minerals in urine that form stones. That same South Carolina study found women in the region had a nearly 45% lifetime risk of developing the condition.
Climate projections suggest this geographic pattern will expand. A widely cited model estimates that the share of the U.S. population living in high-risk zones will grow from 40% in 2000 to 56% by 2050, and to 70% by 2095. That could mean 1.6 to 2.2 million additional lifetime cases by mid-century, concentrated in California, Texas, Florida, and the Eastern Seaboard. The body responds to heat relatively quickly: one study found peak stone formation occurred just 90 days after military personnel deployed to hot, arid climates.
Types of Kidney Stones
Not all kidney stones are the same, and knowing the type matters because it determines what dietary changes can help prevent the next one.
- Calcium oxalate stones account for 35 to 70% of all cases, making them by far the most common. They form when calcium binds with oxalate, a compound found in foods like spinach, nuts, and chocolate. Despite the name, restricting calcium intake doesn’t help and can actually increase risk. The key is reducing oxalate-heavy foods and staying well hydrated.
- Struvite stones make up about 15% of cases. They tend to form after urinary tract infections and can grow quickly, sometimes filling a large portion of the kidney.
- Uric acid stones represent roughly 10% of stones. They’re linked to diets high in animal protein and to conditions like gout. Urine that’s consistently acidic creates the environment for these stones to form.
- Cystine stones are rare, accounting for about 2% of cases. They result from an inherited condition that causes the kidneys to excrete too much of a specific amino acid.
Why Rates Keep Climbing
Kidney stones were less common a generation ago. Several overlapping trends explain the rise. Obesity is one of the strongest risk factors: excess body weight changes the chemical composition of urine in ways that promote stone formation, increasing the excretion of calcium, oxalate, and uric acid. As obesity rates have climbed worldwide, stone rates have followed. Metabolic conditions like diabetes and metabolic syndrome carry similar effects.
Dietary patterns also play a role. Higher sodium intake pulls more calcium into the urine. Diets heavy in animal protein make urine more acidic. Inadequate fluid intake, especially in people who drink sugary beverages instead of water, concentrates the minerals that crystallize into stones. Rising temperatures compound all of these factors by increasing the amount of fluid lost to sweat, particularly for people who don’t compensate by drinking more water.
The combination of these forces means kidney stones are no longer a condition primarily affecting middle-aged men. They’re increasingly common in women, in younger adults, in children, and in geographic regions that were previously lower risk. For a condition that already affects nearly one in ten American adults, the trajectory points toward kidney stones becoming even more prevalent in the coming decades.