Kidney stones do not appear out of nowhere. They form because of a specific chemistry problem in your urine — too much of certain substances, not enough of others, and not enough water to keep everything dissolved. Understanding what causes kidney stones is the first step toward preventing them.
In this guide, we break down the real causes of kidney stones in plain English: how they form, which foods and habits raise your risk, which medical conditions play a role, and which factors are actually within your control.
The Basic Chemistry Behind Kidney Stones
Every day, your kidneys filter waste and extra water out of your blood. The result is urine, which carries dissolved minerals like calcium, oxalate, uric acid, phosphate, sodium, and citrate.
Stones form when three things happen at the same time:
- Urine becomes too concentrated. There is not enough water to keep minerals dissolved.
- Stone-forming substances rise. Levels of calcium, oxalate, uric acid, or cystine climb.
- Stone-preventing substances drop. Levels of citrate — a natural inhibitor — fall.
When these conditions line up, minerals crystallize, clump together, and grow into stones. Over months or even years, those crystals can turn into stones large enough to cause pain and blockage.
The Main Causes of Kidney Stones
1. Not Drinking Enough Water
Dehydration is the single most important cause of kidney stones. When you drink too little, your urine becomes concentrated, and stone-forming minerals crystallize more easily. People living in hot climates, athletes, outdoor workers, and anyone who simply forgets to drink water are at higher risk.
Most stone-prevention guidelines suggest drinking enough fluid to produce at least 2 to 2.5 liters of urine per day. Pale yellow urine is a good visual cue.
2. A High-Sodium Diet
Salt does not directly form stones, but it makes the kidneys dump more calcium into your urine. More urinary calcium means more raw material for calcium-based stones.
Most sodium in the American diet does not come from the salt shaker — it comes from packaged and restaurant foods. Cutting back on processed foods is one of the most effective changes stone formers can make.
3. Too Much Animal Protein
Diets very high in meat, poultry, and seafood raise uric acid, increase urinary calcium, and lower urinary citrate. All three shifts favor stone formation. This does not mean you must eliminate animal protein — only that balancing it with plant proteins and vegetables helps.
4. Diets High in Oxalate (for Some People)
Oxalate is a natural compound in many plant foods. When it binds with calcium in the urine (instead of the gut), it can form calcium oxalate stones — the most common type. High-oxalate foods include spinach, rhubarb, beets, almonds, and certain teas. Most people do not need to eliminate these foods, but stone formers should keep portions reasonable and pair them with calcium-containing foods.
Learn more in our dedicated guide on calcium oxalate stones.
5. Not Enough Dietary Calcium
Counter-intuitively, low dietary calcium can actually cause more kidney stones. When calcium is present in the gut, it binds oxalate and prevents it from reaching the kidneys. Cutting calcium too aggressively frees more oxalate to be absorbed and excreted.
Getting the recommended calcium from food — spread throughout the day — helps most stone formers.
6. Too Much Added Sugar
Diets high in added sugars, especially fructose from sodas and sweetened drinks, are linked to higher stone risk. Sugary drinks may also crowd out water intake, compounding dehydration.
7. Being Overweight or Obese
Higher body weight is linked to lower urine pH (more acidic urine), which favors uric acid stones, and higher urinary calcium and oxalate. Insulin resistance also plays a role in changing urine chemistry. Even modest weight loss can improve stone risk.
8. Certain Medical Conditions
Conditions that raise stone risk include:
- Chronic urinary tract infections (linked to struvite stones)
- Gout and hyperuricemia (uric acid stones)
- Hyperparathyroidism (raises blood calcium and calcium in urine)
- Inflammatory bowel disease (Crohn's, ulcerative colitis)
- Chronic diarrhea
- Bariatric surgery and other malabsorptive surgeries
- Renal tubular acidosis
- Cystinuria (inherited cause of cystine stones)
- Diabetes and metabolic syndrome
- Chronic dehydration disorders
9. Medications
Some medications raise stone risk directly or indirectly:
- Certain diuretics
- Long-term high-dose calcium or vitamin D supplements
- Some HIV medications
- Topiramate and other anti-seizure drugs
- High-dose vitamin C
- Certain antacids used long-term
Never stop a prescribed medication without talking to your doctor — but do bring up your stone history so they can adjust when possible.
10. Genetics and Family History
Kidney stones tend to run in families. Part of this is inherited urine chemistry; part is shared eating habits and environment. Some rare stones, like cystine stones, are caused by a specific genetic disorder (cystinuria).
Modifiable vs. Non-Modifiable Risk Factors
| What You Can Change | What You Cannot Change |
|---|---|
| Daily fluid intake | Family history |
| Sodium intake | Age (risk rises in adulthood) |
| Animal protein intake | Sex (men are at higher risk overall) |
| Sugar and soda intake | Certain genetic disorders |
| Body weight | Climate you live in |
| Dietary calcium (from food) | Personal history of a prior stone |
Why Kidney Stones Are Becoming More Common
Rates of kidney stones have been climbing steadily for decades. Researchers point to several factors:
- Increases in obesity and metabolic disease
- Diets higher in processed food and sodium
- Higher intake of sugary drinks
- Warmer average temperatures and dehydration
- Aging population
- Widespread use of certain medications
The good news is that all of these are influenced by lifestyle — meaning prevention has real leverage.
How Doctors Identify Your Specific Causes
If you have had a kidney stone, your doctor may recommend:
- Stone analysis — sending a passed or removed stone to a lab to identify its type.
- Blood tests — measuring calcium, uric acid, kidney function, and parathyroid hormone.
- 24-hour urine collection — the gold standard for understanding your unique urine chemistry.
- Imaging — to identify silent stones still in the kidney.
A 24-hour urine test is especially valuable because it measures actual levels of calcium, oxalate, uric acid, citrate, sodium, and urine volume. Those numbers guide a personalized prevention plan.
A Note About Children
Kidney stones in children are rising faster than in adults. Common contributing causes include high-sodium diets, low water intake, obesity, and, in some cases, inherited disorders. Any child with a suspected stone should be evaluated by a pediatric urologist.
Realistic Next Steps
If you have already had a stone, or you have strong risk factors, focus on the changes with the biggest impact:
- Drink water throughout the day — every day
- Cut sodium by cooking more meals at home
- Balance animal protein with plant proteins
- Get calcium from food, not supplements
- Limit sugary drinks and sodas
- Work on gradual, sustainable weight loss if needed
- Ask your doctor about a 24-hour urine collection
For a full step-by-step approach, see our detailed kidney stone prevention guide.
References
- National Kidney Foundation — Kidney Stones and Diet.
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK / NIH) — Causes of Kidney Stones.
- Mayo Clinic — Kidney Stones: Causes and Risk Factors.
- Cleveland Clinic — Kidney Stones: Causes and Prevention.
- American Urological Association — Medical Management of Kidney Stones Guideline.
The Bottom Line
Kidney stones are caused by a mismatch in urine chemistry — and most of the factors that create that mismatch are within your control. Hydration, sodium, protein balance, dietary calcium, sugar intake, weight, and management of underlying medical conditions all matter. Understanding your personal causes is the key to a prevention plan you can stick with.
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