Kidney stones are small, hard mineral deposits that form inside your kidneys. They can be as tiny as a grain of sand or, in rarer cases, as large as a golf ball. While they usually begin silently, once a stone starts moving through the urinary tract, it can cause some of the most intense pain a person will ever experience.
The good news: kidney stones are largely preventable. Understanding what they are, why they form, and which foods and habits raise or lower your risk gives you real control — often more than people realize.
What Exactly Is a Kidney Stone?
Your kidneys filter about 50 gallons of blood every day, removing waste and extra water as urine. Dissolved in that urine are minerals and salts like calcium, oxalate, uric acid, sodium, and phosphate. Under the right conditions, those minerals can crystallize, clump together, and grow into a solid mass — a kidney stone.
Stones can stay in the kidney without causing symptoms, sometimes for years. Problems usually start when a stone breaks free and travels down the ureter, the thin tube that connects each kidney to the bladder.
Common Symptoms
Kidney stone symptoms often appear suddenly and may include:
- Severe pain in the side, back, or lower abdomen
- Pain that comes in waves and shifts as the stone moves
- Pain or burning during urination
- Pink, red, or brown urine (blood)
- Cloudy or foul-smelling urine
- Frequent, urgent need to urinate
- Nausea and vomiting
- Fever and chills (a possible sign of infection — seek medical care)
The Main Types of Kidney Stones
Not all kidney stones are the same. Knowing your stone type matters because different stones respond to different dietary and medical strategies.
| Stone Type | Approximate Share | Key Contributors |
|---|---|---|
| Calcium Oxalate | ~70–80% | High oxalate, low calcium intake, dehydration |
| Calcium Phosphate | ~10–15% | High urine pH, certain metabolic conditions |
| Uric Acid | ~5–10% | High animal protein intake, acidic urine, gout |
| Struvite | ~5–10% | Urinary tract infections |
| Cystine | <1% | Rare inherited disorder (cystinuria) |
Calcium Oxalate Stones
The most common type by far. Despite the name, these stones are less about too much dietary calcium and more about too much oxalate combined with too little calcium at meals. When you eat calcium and oxalate together, they bind in the gut and pass out of the body harmlessly.
Calcium Phosphate Stones
Less common than oxalate stones. They tend to form when urine is more alkaline and are often linked to specific metabolic conditions, so they usually require a tailored medical evaluation.
Uric Acid Stones
These form when urine is consistently too acidic. Diets very high in animal protein (especially organ meats and shellfish) and conditions like gout increase risk. Moderating protein and staying well-hydrated help.
Struvite Stones
Struvite stones grow in response to urinary tract infections and can become large quickly. They are treated medically, and the underlying infection must be resolved.
Cystine Stones
Cystine stones are rare and caused by an inherited genetic disorder called cystinuria, which makes the kidneys leak too much of the amino acid cystine into the urine.
Why Do Kidney Stones Form?
Stones form when three things happen at the same time:
- Urine is too concentrated. Not enough water dilutes stone-forming minerals.
- Levels of stone-forming substances are too high (for example, oxalate, uric acid, or cystine).
- Levels of stone-preventing substances are too low (for example, citrate).
Many factors can push those levels in the wrong direction:
- Chronic dehydration
- High-sodium diet
- Very high animal protein intake
- Very high oxalate intake without matching calcium
- Excess sugar and ultra-processed foods
- Obesity and metabolic syndrome
- Family history of stones
- Certain medications and medical conditions
Who Is at Risk?
Kidney stones affect about 1 in 10 people at some point in life, according to the National Kidney Foundation. Risk is higher in men, though rates in women have been climbing. People who have already had one stone are at especially high risk of forming another — which is why prevention is worth the effort.
Other risk factors include:
- Living or working in hot, dry climates
- Diets high in sodium, sugar, and animal protein
- Low fluid intake
- Obesity, diabetes, and high blood pressure
- Certain gastrointestinal conditions and bariatric surgery
How Are Kidney Stones Diagnosed?
Doctors typically diagnose kidney stones using a combination of:
- Physical exam and detailed history
- Urine tests (to look for blood, crystals, and infection)
- Blood tests (to check kidney function and mineral levels)
- Imaging — most often a low-dose CT scan or ultrasound
- Stone analysis after a stone is passed or removed, to identify the type
Stone analysis is one of the most useful tests, because knowing the type shapes prevention.
How Are Kidney Stones Treated?
Treatment depends on size, location, symptoms, and stone type.
- Small stones often pass on their own with fluids and pain management.
- Medications like alpha-blockers can relax the ureter and help stones pass.
- Shock wave lithotripsy (SWL) uses sound waves to break stones into smaller pieces.
- Ureteroscopy uses a thin scope to remove or break up stones directly.
- Percutaneous nephrolithotomy is a surgical option for very large stones.
How to Prevent Kidney Stones
Prevention is where you have the most leverage. Core habits that help most stone types:
1. Drink Enough Water
Hydration is the single most powerful tool. Most guidelines suggest aiming for 2.5–3 liters of fluid a day for stone-formers, or enough to produce at least 2 liters of urine daily. Pale yellow urine is a good target.
2. Moderate Sodium
High sodium intake increases how much calcium your kidneys dump into the urine, raising stone risk. Most adults should stay under about 2,300 mg per day; people with stones often benefit from going lower.
3. Get Calcium From Food
Aim for the daily recommended amount of calcium — mostly from food. Calcium binds oxalate in the gut and actually protects against calcium oxalate stones.
4. Watch Oxalate Intake if You Form Oxalate Stones
Very high-oxalate foods (like raw spinach, rhubarb, almonds, and beets) can drive up urinary oxalate. You do not need to eliminate them — pair them with calcium-containing foods and keep portions reasonable.
5. Moderate Animal Protein
Very high intake of meat, poultry, and seafood increases uric acid and can lower urinary citrate. Balance animal protein with plant-based sources.
6. Eat More Fruits and Vegetables
Most fruits and vegetables raise citrate, a natural stone inhibitor. Diets rich in produce (like the DASH pattern) are consistently linked to lower stone risk.
7. Limit Added Sugar and Sugary Drinks
Sugary sodas, especially those with high-fructose corn syrup, have been linked to higher stone risk. Water, citrus-infused water, and unsweetened beverages are better daily choices.
When Should You See a Doctor?
Seek medical care right away if you experience:
- Severe pain you cannot control
- Pain with fever or chills (possible infection)
- Blood in the urine
- Persistent nausea or vomiting
- Difficulty urinating
Anyone who has had a kidney stone should also consider a preventive workup — usually including a 24-hour urine test — to build a personalized prevention plan.
Trusted Resources
For more information, these organizations offer reliable, expert-reviewed content:
- National Kidney Foundation (NKF)
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK / NIH)
- Centers for Disease Control and Prevention (CDC)
- Academy of Nutrition and Dietetics
The Bottom Line
Kidney stones are common, painful, and — for most people — very preventable. The right combination of hydration, balanced nutrition, and awareness of your personal stone type can dramatically reduce your risk of ever forming another one. If you have already had a stone, work with your doctor and a registered dietitian to build a long-term prevention plan you can actually stick with.
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