Quick Answer
Kidney stones form when your urine contains more crystal-forming substances (calcium, oxalate, uric acid) than the fluid in your urine can dilute.
#1 Culprit: NOT ENOUGH WATER.
4 Types of Stones & Their Causes
1. Calcium Stones (Most Common)
Usually calcium oxalate. Caused by high oxalate foods (spinach, peanuts, chocolate) or high doses of Vitamin D. Surprise: Eating calcium-rich foods actually prevents them (but taking calcium pills can cause them).
2. Uric Acid Stones
Form in people who don't drink enough fluid, eat a high-protein diet (lots of meat), or have gout.
3. Struvite Stones
Form in response to an infection, like a urinary tract infection (UTI). These can grow quickly and become quite large.
4. Cystine Stones
Caused by a hereditary disorder (cystinuria) that causes the kidneys to excrete too much of a specific amino acid.
How to Prevent Them
Drink More
Aim for 2.5 to 3 liters of water a day.
Limit Sodium
Salt increases calcium in your urine.
Medical Review
Reviewed by: Ricardo Hamilton, MD
Last Updated: December 15, 2025
Sources: National Kidney Foundation, Mayo Clinic