Kidney Stones | Causes & Risk Factors


What causes kidney stones?

There are four types of kidney stones:

  • Calcium stone: This is the most common type of kidney stone. Calcium that is not used by your bones and muscles goes to your kidneys. Usually, the kidneys will get rid of the extra calcium through the urine. Calcium stones occur when some of the calcium remains in the kidneys and collects over time.
  • Struvite stone: A struvite stone is more common in women. It usually forms after a chronic urinary tract infection. These stones are usually made of ammonia.
  • Uric acid stone: A uric acid stone forms when there is too much uric acid in the urine. You may be at risk for this type of stone if you eat a high-protein diet or if you’ve received chemotherapy.
  • Cystine stone: A cystine stone is not very common. The disease that causes cystine stones to form runs in families and is called cystinuria.

Risk Factors

  • Not drinking enough fluids, especially water
  • Family history of kidney stones
  • Eating a diet high in protein and sodium but low in fiber
  • Being a man
  • Being between 20 and 70 years of age
  • Being bed-ridden or immobile for a long period of time
  • Certain medications


Medical Management of Common Urinary Calculi by PK Pietrow, M.D. and ME Karellas, M.D. (American Family Physician June 01, 2006,

Written by editorial staff

Reviewed/Updated: 03/14
Created: 07/06