Kidney stones in women are caused by a combination of dietary habits, hormonal shifts, underlying health conditions, and anatomical factors unique to female biology. While stones have historically been more common in men, that gap is shrinking fast. Data from the National Health and Nutrition Examination Survey shows that kidney stone prevalence among U.S. women rose steadily from 6.5% in 2007–2008 to 9.4% in 2017–2018, while rates in men held relatively flat. Today, roughly 1 in 10 American women will deal with a kidney stone at some point.
Too Little Fluid, Too Much Salt
The most straightforward cause is not drinking enough water. When urine becomes concentrated, minerals like calcium and oxalate can crystallize and clump together. Clinical guidelines recommend producing at least 2.5 liters of urine per day to keep stone risk low, though research shows that even modest increases in fluid intake can cut recurrence risk by more than half.
High sodium intake is a less obvious but powerful driver. When you eat a lot of salt, your kidneys flush out more sodium, and calcium gets dragged along with it. An extra 6 grams of salt per day (roughly a teaspoon) can increase urinary calcium by about 40 milligrams daily in healthy people. In someone who has already formed stones, that same extra salt can double the calcium loss to around 80 milligrams per day. People consuming more than 10 grams of salt daily are roughly five times more likely to have excess calcium in their urine compared to those eating less. Salt also lowers urinary citrate, a substance that normally prevents crystals from forming. In studies where salt intake jumped from about 3 grams to nearly 15 grams per day, citrate levels dropped by about 20%.
Animal protein compounds the problem. Diets high in both salt and animal protein raise urinary calcium in an additive way, meaning the two together are worse than either alone.
Hormonal Changes and Menopause
Estrogen plays a protective role against kidney stones. It slows bone breakdown (which releases calcium into the blood) and helps the kidneys reabsorb calcium rather than dump it into urine. Estrogen also appears to support healthy citrate excretion, and citrate is one of the body’s main defenses against crystal formation. Studies show that citrate levels in women fluctuate with estrogen across the menstrual cycle, and premenopausal women generally excrete less calcium and oxalate and more citrate than men of the same age.
When estrogen levels decline during menopause, those protective effects weaken. More calcium ends up in the urine, citrate drops, and stone risk climbs. This hormonal shift is one reason kidney stone rates in women increase significantly after midlife and helps explain the closing gender gap in overall prevalence.
Pregnancy Raises Risk Temporarily
Pregnancy creates several conditions that favor stone formation. Early in pregnancy, rising progesterone relaxes and widens the ureters (the tubes connecting the kidneys to the bladder), which slows urine flow and allows minerals more time to crystallize. The kidneys also filter blood at a higher rate during pregnancy, which pushes more calcium into the urine. Urinary tract infections, already more common in pregnant women, add another layer of risk. These factors combine to make kidney stones a recognized complication of pregnancy, though they remain relatively uncommon overall.
UTIs and Struvite Stones
Most kidney stones are made of calcium oxalate or calcium phosphate. But women face a disproportionate risk for a different type called struvite stones, which form after urinary tract infections. Certain bacteria change the chemical environment of urine, making it less acidic and creating ideal conditions for struvite crystals. Because UTIs occur far more often in women, struvite stones are also more common in women. Recurrent or untreated infections are the biggest risk factor. Unlike other stone types, struvite stones can grow quickly and become quite large, sometimes filling an entire section of the kidney.
Obesity and Metabolic Syndrome
Carrying excess weight is one of the strongest predictors of kidney stone formation. Research from the National Kidney Foundation found that people with all five traits of metabolic syndrome (large waist circumference, high blood sugar, high triglycerides, low HDL cholesterol, and high blood pressure) were roughly twice as likely to have kidney stones as those without the syndrome. Even having just a few of those traits raised risk: stone prevalence climbed from 3% among people with none to 7.5% among those with three. For women, the waist circumference threshold associated with increased risk is 35 inches or more.
Insulin resistance, a core feature of metabolic syndrome and type 2 diabetes, makes urine more acidic. Acidic urine favors the formation of uric acid stones, a type that can be particularly common in people with diabetes or prediabetes.
Medications and Supplements
Several commonly used medications can promote stone formation. Topiramate, prescribed for migraines and seizures, is linked to calcium phosphate stones. Calcium-based antacids, vitamin C supplements in high doses, overuse of laxatives, and certain medications for depression can also raise risk. If you take any of these regularly and have a history of stones, it is worth discussing alternatives or monitoring strategies with your provider.
Dietary Calcium: A Counterintuitive Finding
Many women assume they should cut back on calcium to prevent stones, but the opposite is true. Research published in Mayo Clinic Proceedings found that a daily calcium intake of about 1,200 milligrams from food (the same amount recommended for the general population) was associated with the lowest risk of stone formation. Calcium from food binds to oxalate in the digestive tract, preventing it from being absorbed and eventually reaching the kidneys. The key distinction is the source: calcium from dairy and other foods is protective, while calcium supplements taken between meals may increase risk because they don’t interact with oxalate during digestion.
Telling Stones Apart From a UTI
Because UTIs and kidney stones share symptoms like frequent urination, cloudy urine, and discomfort, many women initially mistake one for the other. The pain pattern is the most reliable difference. UTI pain typically centers in the lower abdomen near the pubic bone and causes a burning sensation during urination. Kidney stone pain tends to hit the back, side, or flank in sharp, stabbing waves and can radiate to the lower abdomen or groin. Visible blood in the urine (pink, red, or brown) is more characteristic of stones than infections. Nausea and vomiting commonly accompany stones but are unusual with a straightforward UTI. Both conditions can cause fever, so that alone won’t distinguish them.
Adding to the confusion, a kidney stone that blocks urine flow can actually trigger a UTI, meaning both problems can occur simultaneously. Any combination of severe flank pain, blood in the urine, or fever warrants prompt evaluation.