Most kidney stones smaller than 5 mm will pass on their own with enough fluids, pain management, and time. Stones 4 mm or smaller pass spontaneously about 72 to 87% of the time, while 5 mm stones have roughly a 60% chance. Once stones reach 10 mm or larger, that rate drops to 27%, and medical intervention is usually needed. What you do in the hours and days after symptoms start can make a real difference in how quickly and comfortably a stone passes.
Managing the Pain
Kidney stone pain is notoriously intense, often described as worse than childbirth. It hits in waves as the stone moves through the ureter, the narrow tube connecting your kidney to your bladder. Anti-inflammatory painkillers (NSAIDs like ibuprofen or naproxen) are the first-line choice because they do two things at once: they reduce pain and they decrease swelling in the ureter, which helps the stone move. A Cochrane review of clinical trials found that NSAIDs significantly reduced renal colic pain within 30 minutes compared to placebo.
A heating pad on your lower back or side can also help relax the muscles around the ureter. Warm baths work similarly. These won’t speed up stone passage, but they can take the edge off between pain spikes.
How Much Water You Actually Need
Fluid intake is the single most important thing you control during a stone episode. Drinking enough water keeps urine dilute and helps push the stone along. People actively passing a stone, or anyone who has had one before, should aim for at least 2 liters (8 cups) and ideally 3 liters (12 cups) of water per day, according to guidance from UT Southwestern Medical Center. That’s more than the standard “8 glasses a day” advice, and it needs to be spread throughout the day, including before bed.
A good benchmark: your urine should be pale yellow or nearly clear. If it’s dark, you’re not drinking enough. Avoid drinks that dehydrate you, particularly alcohol and excessive caffeine, while you’re trying to pass a stone.
Medications That Help Stones Pass
For stones between 5 and 10 mm, your doctor may prescribe a medication called tamsulosin, which relaxes the smooth muscle in the ureter and widens the passage. In a study published through the American Academy of Family Physicians, tamsulosin increased the stone passage rate from 61% to 83% for stones in this size range. This approach is called medical expulsive therapy, and it’s typically tried for a few weeks before considering a procedure. The medication was originally developed for prostate issues, but it works on the same type of muscle tissue in the urinary tract.
When a Stone Needs Emergency Attention
Most stones are painful but not dangerous. A few situations change that equation. Seek immediate care if you experience:
- Pain so severe you cannot sit still or find any comfortable position
- Pain with fever and chills, which can signal an infection behind a blocked stone
- Persistent nausea and vomiting that prevents you from keeping fluids down
- Blood in your urine
- Difficulty passing urine or a complete stop in urine flow
A stone that completely blocks the ureter, especially with an infection present, can become a urological emergency. Fever and chills alongside stone symptoms should never be ignored.
The Calcium Paradox
Most kidney stones are made of calcium oxalate, so many people assume they should cut calcium from their diet. This is one of the most common mistakes stone formers make, and it actually increases risk. Here’s why: when you eat calcium-rich foods alongside meals, the calcium binds to oxalate in your digestive tract before either gets absorbed. That bound complex passes through your stool instead of reaching your kidneys. A low-calcium diet does the opposite. It leaves oxalate free to be absorbed into your bloodstream and filtered through your kidneys, where it can crystallize into stones.
Research published in Mayo Clinic Proceedings confirmed that diets with balanced calcium and oxalate content reduce oxalate absorption, while low-calcium diets promote it. The key is getting calcium from food (dairy, fortified plant milks, leafy greens) rather than supplements, and eating it with meals so it can intercept oxalate in the gut.
Foods to Watch
For people with calcium oxalate stones, limiting dietary oxalate to 40 to 50 mg per day is a commonly recommended target. Some of the highest-oxalate foods include spinach, rhubarb, beets, nuts (especially almonds and cashews), chocolate, and sweet potatoes. You don’t have to eliminate these entirely, but eating large amounts regularly raises your risk. Pairing high-oxalate foods with calcium-rich foods at the same meal helps offset the effect.
Reducing sodium matters too. High salt intake causes your kidneys to excrete more calcium into the urine, giving stones more raw material. Processed foods, canned soups, and fast food are the biggest culprits. Cutting back on animal protein, particularly red meat, also helps because it increases uric acid and lowers citrate levels in urine, both of which promote stone formation.
Lemon Juice and Citrate
Citrate is a natural stone inhibitor. It binds to calcium in urine and prevents crystals from clumping together. Many stone formers have low urinary citrate, a condition that makes recurrence more likely. Doctors sometimes prescribe potassium citrate supplements, but lemon juice is a dietary alternative that provides meaningful amounts. About 85 cc (roughly one-third cup) of pure lemon juice contains approximately 60 milliequivalents of citrate, which matches the typical therapeutic dose of prescription potassium citrate.
A practical approach: squeeze half a lemon into a glass of water several times a day. This also helps increase your overall fluid intake. The evidence is strongest for calcium-based stones. For uric acid stones, citrate works differently by raising urine pH, making urine less acidic and creating an environment where uric acid crystals can actually dissolve.
Uric Acid Stones Are Different
About 10 to 15% of kidney stones are made of uric acid rather than calcium. These form in acidic urine and have a unique advantage: they can sometimes be dissolved without surgery. The goal is to make your urine more alkaline through diet changes and, in many cases, prescribed alkalinizing agents. Reducing purine-rich foods (organ meats, shellfish, red meat, and beer) lowers uric acid production. Your doctor can monitor your urine pH and adjust treatment accordingly.
What Passing a Stone Looks Like
Once a stone leaves the kidney, it typically takes one to three weeks to reach the bladder, though smaller stones can pass in days. The worst pain usually occurs while the stone is in the ureter. Once it drops into the bladder, most people feel dramatic relief. Passing the stone from the bladder out through the urethra is usually painless or mildly uncomfortable.
Your doctor will likely ask you to strain your urine through a fine mesh or filter to catch the stone. This matters because lab analysis of the stone tells you exactly what type it is, which shapes your prevention strategy going forward. Without knowing the composition, dietary changes are guesswork. Save any fragments you catch, even small ones, and bring them to your follow-up appointment.
Preventing the Next Stone
Kidney stones recur in roughly half of people within five to ten years. Prevention is largely about daily habits. Drinking 2 to 3 liters of water daily is the single most effective measure. Beyond that, eat calcium with meals, limit sodium and animal protein, keep oxalate intake moderate, and add citrus to your water. If you’ve had more than one stone, a 24-hour urine collection test can identify your specific metabolic risk factors, letting your doctor tailor prevention precisely to your body chemistry.