Kidney stones are a sign that minerals and salts in your urine have concentrated enough to form solid crystals. Most stones are made of calcium oxalate or calcium phosphate. Passing one is often a signal of an underlying pattern — low urine volume, a diet high in sodium or oxalate, or in some cases a medical condition that raises your risk. The stone itself is a symptom. What caused it is the real question.
Most people who form a stone never form another. For those who do, the pattern usually points to something you can change. Knowing what your stone is made of, and why it formed, matters more than the stone itself.
What Are Kidney Stones a Sign Of?
A kidney stone is a sign that your urine became supersaturated with stone-forming minerals. When urine is too concentrated, or when it lacks enough water and natural inhibitors, crystals can clump together and grow into a stone.
The most common type — calcium oxalate — points to several possible factors. Low fluid intake is the most frequent. A diet very high in sodium raises calcium in the urine. So does eating large amounts of high-oxalate foods like spinach, rhubarb, and almonds, especially when combined with low fluid intake. Some people simply absorb more oxalate from food than others.
Uric acid stones are a sign of persistently acidic urine. They are more common in people with gout, type 2 diabetes, obesity, or a diet heavy in animal protein. Struvite stones are different — they are a sign of repeated urinary tract infections caused by certain bacteria that produce urease, an enzyme that makes urine more alkaline and encourages stone growth. These stones can grow quickly and are more common in women with recurrent infections.
Cystine stones are rare and are a sign of a genetic condition called cystinuria, in which the kidneys leak an amino acid called cystine into the urine. This is inherited and typically shows up earlier in life than other stone types.
In short, the stone type tells you a lot. If you have passed a stone, ask your doctor whether it was analyzed. Stone composition guides what to do next.
What Symptoms Suggest You Have a Kidney Stone?
The classic symptom is severe, cramping pain that starts in your back or side and moves toward your lower abdomen and groin as the stone travels down the ureter. The pain often comes in waves rather than staying constant.
Other common signs include:
- Blood in the urine, which may be pink, red, or brown, or visible only under a microscope
- Nausea and vomiting, often triggered by the pain itself
- Pain or burning when you urinate, especially as the stone nears the bladder
- A frequent urge to urinate or urinating small amounts
- Cloudy or foul-smelling urine, which may suggest infection
Fever and chills are not typical of an uncomplicated stone. When they occur alongside stone symptoms, they can signal an infected urinary tract and warrant urgent medical attention. An obstructed kidney with infection is a medical emergency.
Small stones may pass with little or no pain. Larger stones, or stones that block urine flow, tend to cause the severe pain people describe.
What Causes Kidney Stones to Form?
Stones form when the balance in your urine tips toward crystallization. Several forces drive that shift.
Low urine volume is the single biggest contributor. When you don’t drink enough water, urine becomes concentrated and minerals have less fluid to stay dissolved in. This is why people in hot climates and those who work physically demanding jobs are at higher risk.
Diet plays a direct role. High sodium intake increases calcium excretion in urine. A diet heavy in animal protein raises uric acid and lowers urine citrate, a natural stone inhibitor. High-oxalate foods contribute in some people, though the effect varies widely.
Medical conditions raise risk in specific ways. Hyperparathyroidism causes high blood calcium. Recurrent urinary infections can lead to struvite stones. Gout, obesity, and type 2 diabetes are associated with uric acid stones. Some medications, including certain diuretics and calcium supplements taken without food, can increase risk in some people.
Family history matters. A parent or sibling with stones raises your own risk, and some inherited conditions directly cause stone formation.
One point that often gets lost: dietary calcium is not the villain. In fact, eating normal amounts of calcium with meals can lower oxalate absorption and reduce stone risk. The problem is usually too little calcium in the diet, not too much.
When Should You See a Doctor?
See a doctor if you have severe pain in your back or side that doesn’t ease, blood in your urine, fever with urinary symptoms, or pain so intense you can’t sit still. These are signs that need prompt evaluation.
Get emergency care if you have fever with chills and flank pain, if you can’t urinate at all, or if you have severe nausea and vomiting that prevent you from keeping fluids down. An infected or fully obstructed urinary tract can become serious quickly.
For milder symptoms — intermittent discomfort, a history of small stones, or blood in the urine without pain — a prompt but non-emergency appointment is reasonable. Your doctor can check for stones and look for underlying causes.
How Are Kidney Stones Diagnosed?
Diagnosis usually starts with your symptoms and a urine test. A urinalysis can detect blood, crystals, and signs of infection. Blood tests check kidney function and levels of calcium, uric acid, and other markers.
Imaging confirms the diagnosis. A non-contrast CT scan of the abdomen and pelvis is the most accurate way to find stones and see whether one is blocking urine flow. Ultrasound is often used first in certain situations, including pregnancy, where avoiding radiation matters.
If you pass a stone, your doctor may ask you to collect it so it can be analyzed. Knowing the stone’s composition is one of the most useful pieces of information you can get, because it guides prevention directly.
For people who form stones repeatedly, a 24-hour urine collection can show whether you are excreting too much calcium, oxalate, uric acid, or too little citrate. That test helps tailor prevention.
What Does a Kidney Stone Mean for Your Long-Term Health?
For most people, a single stone is an isolated event. Roughly half of those who have one stone will form another within several years, though the exact rate varies widely depending on the person and the cause.
The bigger picture depends on why the stone formed. If it was low fluid intake, the fix is straightforward. If it reflects an underlying condition like hyperparathyroidism, gout, or a genetic disorder, that condition needs its own attention.
Kidney stones are also associated with a higher long-term risk of chronic kidney disease in some people, particularly those who form stones repeatedly or have other kidney problems. This association does not mean every stone leads to kidney damage. It does mean that recurrent stones deserve real attention rather than being written off as a minor nuisance.
How Can You Lower Your Risk of Forming Another Stone?
The most effective step for most people is drinking enough fluid to keep urine pale and dilute. Many clinicians advise aiming for enough water to produce roughly 2 to 2.5 liters of urine a day, though the right target depends on your situation. Your doctor can give you a specific goal.
Reducing sodium intake helps because sodium drives calcium into the urine. Eating calcium-rich foods with meals — rather than cutting calcium — actually lowers oxalate absorption in most people. Limiting high-oxalate foods matters mainly for people who absorb oxalate heavily, so it is not a universal rule.
Getting adequate dietary calcium, moderating animal protein, and eating plenty of fruits and vegetables are reasonable general steps. For people with specific stone types, targeted measures apply: uric acid stones may be managed partly by reducing purine-rich foods and, in some cases, medication to raise urine pH. Struvite stones often require addressing the underlying infection, sometimes with surgical removal.
Some people benefit from medications such as thiazide diuretics or potassium citrate, but these are not for everyone. They are typically considered after a stone analysis and sometimes a 24-hour urine test. This is a conversation to have with your doctor, not a step to take on your own.
If you have passed a stone, ask what it was made of. That single question often shapes everything that follows.
Frequently Asked Questions
What is the most common cause of kidney stones?
Low fluid intake is the most common contributor, because it concentrates the minerals that form stones. Diet high in sodium and certain medical conditions also play a role.
Can kidney stones be a sign of something serious?
Most stones are not a sign of serious disease, but some point to underlying conditions like hyperparathyroidism, gout, or a genetic disorder. A stone analysis and, when needed, blood and urine tests help identify the cause.
Do kidney stones mean I have kidney disease?
No. Most people with stones have normal kidney function. Recurrent stones are associated with a higher long-term risk of kidney problems in some people, which is why repeated stones deserve medical attention.
What should I do if I think I have a kidney stone?
See a doctor promptly, especially if you have severe pain, blood in your urine, or fever. Fever with flank pain is an emergency and needs immediate care.
