Kidney Stones: What They Are and How to Lower Your Risk

Kidney stones are hard deposits that form inside the kidneys when certain minerals and salts become concentrated enough in the urine to crystallize. They are common, painful when they pass, and for many people, likely to recur without some changes in diet and habits. Understanding what causes stones and how they are typically managed can make the experience less confusing if you or a family member is affected.

How do kidney stones form?

Urine normally carries dissolved minerals such as calcium, oxalate, and uric acid without any issue. Stones form when these substances become too concentrated, often because of low fluid intake, and begin to crystallize and stick together. Over time, these crystals can grow into stones ranging from the size of a grain of sand to, in less common cases, much larger.

What are the common types of kidney stones?

Calcium oxalate stones are the most common type, forming when calcium combines with oxalate, a compound found naturally in many plant-based foods. Uric acid stones form when urine is consistently too acidic, often linked to diet or conditions like gout. Struvite stones are less common and are usually associated with urinary tract infections. Cystine stones are the rarest and are linked to an inherited condition that causes the kidneys to excrete too much of a particular amino acid. Knowing which type of stone a patient has formed helps guide prevention strategies, since the dietary and medical approach differs by stone type.

What are the symptoms of a kidney stone?

Small stones may pass without any noticeable symptoms at all. Larger stones, or stones that become lodged while moving through the urinary tract, often cause sudden and severe pain in the back or side, pain that can radiate toward the lower abdomen or groin. Other symptoms can include blood in the urine, nausea, and a frequent or urgent need to urinate. Fever combined with stone symptoms can signal an infection and generally warrants prompt medical attention.

Who is most at risk for kidney stones?

Not drinking enough fluids is one of the most significant and modifiable risk factors for kidney stones. Diets high in sodium or animal protein, a family history of stones, certain medical conditions, and having formed a stone before all increase the likelihood of future stones. Climate and lifestyle also play a role, since people who lose more fluid through sweat without replacing it are more prone to concentrated urine.

How can you lower your risk of another stone?

For most people, the single most effective prevention step is drinking enough water throughout the day to keep urine light in color and dilute. Reducing sodium intake, moderating animal protein, and getting adequate dietary calcium from food, rather than avoiding calcium altogether, can also help reduce the risk of calcium stones. Because prevention strategies depend on the type of stone involved, testing to identify stone composition and individual risk factors is often part of a longer-term prevention plan for people who form stones repeatedly.

This article is for general education and is not a substitute for medical advice. Please consult your physician if you suspect a kidney stone or have questions about prevention specific to you.