How Do People Get Kidney Stones? Causes And Risks

Kidney stones form when certain minerals and salts in urine become concentrated enough to clump together into solid crystals. The most common type, calcium oxalate stones, develops when urine contains more oxalate or calcium than the fluid can dilute, or when it lacks enough citrate and other substances that normally keep crystals from sticking. Anyone can get them, but some people are far more prone than others.

How Do People Get Kidney Stones Causes And Risks

Urine is mostly water, but it also carries dissolved waste products. When the balance tips toward too much waste and too little water, those dissolved minerals can start to link up into crystals. Over weeks or months, crystals can grow into a stone.

The process usually involves several factors working together, not a single cause. Dehydration, diet, genetics, certain medical conditions, and some medications can all push the chemistry of urine in the wrong direction.

There are four main stone types, and each forms for somewhat different reasons:

• Calcium oxalate — the most common type, linked to low urine volume, high oxalate intake, and certain metabolic conditions.
• Calcium phosphate — associated with conditions like renal tubular acidosis and some urinary tract infections.
• Struvite — caused by urinary tract infections with bacteria that produce urease, an enzyme that raises urine pH.
• Uric acid — linked to low urine pH, gout, and a diet heavy in animal protein.

What Role Does Dehydration Play?

Low fluid intake is one of the strongest risk factors for kidney stones. When you drink less water, urine becomes more concentrated. Minerals that would normally stay dissolved are packed into less liquid, which makes crystallization more likely.

People who live in hot climates, work outdoors, or exercise heavily without drinking enough are at higher risk. So are people who simply do not feel thirsty often and drink little throughout the day.

The relationship is straightforward: more urine volume means more dilution, and more dilution means minerals are less likely to cluster into stones. Drinking water regularly through the day is one of the few prevention strategies that most clinicians agree on.

How Does Diet Affect Kidney Stone Risk?

Diet matters, but not always in the way people expect. A common misconception is that cutting all calcium from your diet prevents calcium oxalate stones. Research shows the opposite. Getting normal amounts of calcium from food actually helps because calcium binds oxalate in the gut before it can be absorbed and sent to the kidneys.

Several dietary factors are linked to higher stone risk:

• High sodium intake — extra sodium causes the kidneys to excrete more calcium in urine.
• High oxalate foods — spinach, rhubarb, beets, nuts, and chocolate are rich in oxalate. Eating large amounts regularly may raise risk, especially with low calcium intake.
• High animal protein — can lower urine pH and reduce citrate, a natural stone inhibitor.
• High fructose or sugary drinks — some studies link these to higher stone risk, though the evidence is less consistent than for sodium and oxalate.

Potassium-rich fruits and vegetables may help lower risk. Citrate from citrus fruits like lemons and oranges can bind calcium in urine and make stone formation less likely.

Who Is Most at Risk for Kidney Stones?

Kidney stones affect roughly 1 in 11 people in the United States at some point. Men are more likely to get them than women, though the gap has narrowed in recent decades. Most first stones appear between ages 30 and 60.

Risk factors that are well established include:

• A personal or family history of stones
• Previous kidney stone episodes
• Obesity and metabolic syndrome
• Diabetes and high blood pressure
• Gout
• Chronic dehydration
• Certain digestive conditions like Crohn’s disease or ulcerative colitis
• Bariatric surgery, which can change how the gut absorbs oxalate
• Some medications, including certain diuretics and calcium supplements taken without food

Having one stone raises the odds of having another. Recurrence rates are high, which is why doctors often recommend testing to find out what type of stone a person formed.

Can Medical Conditions Cause Kidney Stones?

Yes. Several conditions change the chemistry of urine in ways that promote stone formation.

Hyperparathyroidism causes the parathyroid glands to release too much parathyroid hormone, which raises blood calcium and pushes more calcium into urine. Renal tubular acidosis makes urine too alkaline and lowers citrate levels, which favors calcium phosphate stones. Primary hyperoxaluria is a rare genetic disorder that causes the liver to produce too much oxalate.

Chronic urinary tract infections with certain bacteria can lead to struvite stones. These stones can grow quickly and become large, sometimes filling part of the kidney.

Gout and other conditions that produce high uric acid can lead to uric acid stones, especially when urine is persistently acidic.

What Are the Symptoms of Kidney Stones?

Small stones may pass without any symptoms. Larger stones that block the flow of urine cause severe pain, typically in the flank or lower back, often radiating to the groin. The pain tends to come in waves as the stone moves.

Other common symptoms include blood in the urine, nausea, vomiting, and a frequent urge to urinate. Fever and chills may indicate an infection, which is a medical emergency requiring immediate care.

Pain from a kidney stone is often described as one of the most intense types of pain a person can experience. It is not usually constant. It shifts and intensifies as the stone travels through the ureter.

How Are Kidney Stones Diagnosed and Treated?

Doctors typically use imaging to confirm a stone. A non-contrast CT scan is the most accurate method. Ultrasound is often used first in children and pregnant women to avoid radiation. A urinalysis can show blood or infection, and blood tests can check kidney function and levels of calcium, uric acid, and other substances.

Treatment depends on stone size, location, and symptoms:

• Small stones — often pass on their own with hydration and pain control. Some clinicians prescribe medication to help relax the ureter.
• Medium stones — may require a procedure called extracorporeal shock wave lithotripsy, which uses sound waves to break the stone into smaller pieces.
• Large or blocking stones — may need ureteroscopy or percutaneous nephrolithotomy, procedures that remove or break up the stone directly.

Prevention after a first stone usually focuses on drinking enough water to produce at least 2.5 liters of urine per day, reducing sodium, and eating normal amounts of dietary calcium. Some people benefit from medications like thiazide diuretics, allopurinol, or potassium citrate, depending on their stone type and urine chemistry.

Can Kidney Stones Be Prevented?

Prevention is possible for many people, though not all. The most consistent evidence supports high fluid intake. Beyond that, dietary changes and sometimes medication can lower recurrence risk.

Key steps that most clinicians recommend:

• Drink enough water to keep urine pale yellow
• Limit sodium to less than 2,300 mg per day
• Get calcium from food, not supplements, unless a doctor advises otherwise
• Limit oxalate-rich foods if your urine oxalate is high
• Eat more fruits and vegetables, especially citrus
• Limit animal protein if you form uric acid stones

People who have had more than one stone may benefit from a 24-hour urine collection test. This test measures urine volume, pH, and levels of calcium, oxalate, citrate, and uric acid. The results can guide specific dietary or medication changes.

No prevention strategy works for everyone. Stone type, genetics, and underlying medical conditions all play a role. What works for one person may not work for another.