Most kidney stones pass on their own, and the single biggest factor determining whether yours will is its size. Stones smaller than 4 mm pass about 98% of the time without any procedure. At 5 mm, the odds drop to around 65%, and by 6 mm or larger, the chances fall sharply. While you wait, there are several things you can do to speed the process and manage the pain.
How Size Determines Your Odds
A study published in European Radiology tracked spontaneous passage rates over 20 weeks and found a clear relationship between stone width and the likelihood it would pass without intervention:
- Under 3.5 mm: 98% pass on their own
- 3.5 to 4.4 mm: 81%
- 4.5 to 5.4 mm: 65%
- 5.5 to 6.4 mm: 33%
- 6.5 mm or larger: 9%
If your stone is under 5 mm, your doctor will likely recommend watchful waiting with home management. Larger stones, or stones stuck in the upper part of the ureter, are more likely to need a procedure. The strategies below are most useful for stones in that passable range.
Drink Enough Fluid to Keep Urine Flowing
Staying well hydrated increases urine volume, which helps push the stone through the ureter. The NHS recommends aiming for up to 3 liters (about 100 ounces) of fluid per day. Water is the best choice, though other non-sugary drinks count too.
You don’t need to chug enormous amounts at once. Steady intake throughout the day keeps a consistent flow of urine moving through the system. If you’re vomiting and can’t keep fluids down, that changes the equation and you may need IV fluids in an urgent care or emergency setting.
Managing the Pain Effectively
Kidney stone pain, called renal colic, can be severe. It happens when the stone blocks urine flow and pressure builds in the kidney and ureter. Anti-inflammatory pain relievers like ibuprofen and naproxen are the first-line choice for a good reason: they don’t just mask the pain, they reduce the inflammation and swelling around the stone that causes it.
A large Cochrane review comparing anti-inflammatory pain relievers to opioid painkillers found that patients who took anti-inflammatories achieved greater pain reduction and were 25% less likely to need additional medication. Opioids, on the other hand, caused significantly more vomiting. This was especially true for one older opioid called pethidine (meperidine), which caused nausea at much higher rates and is now generally discouraged for kidney stone pain.
For at-home management, over-the-counter ibuprofen or naproxen taken as directed on the label is a reasonable starting point. A warm bath or heating pad on your back or side can also help relax the muscles around the ureter and take the edge off cramping between doses.
Alpha-Blocker Medication
Your doctor may prescribe a type of medication that relaxes the smooth muscle lining the ureter, making it easier for the stone to travel through. This approach is called medical expulsive therapy. These drugs were originally developed for prostate issues, but they work well on the ureter because the muscle tissue is similar.
A meta-analysis of nearly 6,000 patients across 55 trials found that this class of medication improved stone clearance rates by 49% compared to no treatment. The American Urological Association’s own analysis found a 73% stone-free rate with the medication versus 54% without it, specifically for stones under 10 mm in the lower ureter. The benefit is most pronounced for stones between 5 and 10 mm, right in the zone where passage is possible but not guaranteed.
Side effects are generally mild. Some people experience dizziness or lightheadedness, particularly when standing up quickly. The medication is typically taken once daily for up to four weeks or until the stone passes.
Movement and Sleep Position
Light physical activity like walking may help a stone move along. While there isn’t strong trial data proving that walking speeds passage, most urologists recommend staying active rather than lying still, since gravity and movement can help the stone progress through the ureter.
Sleep position is one area where there is data. A study found that patients who slept on the same side as their stone were stone-free 88% of the time at three months, compared to 70% of those who slept on the opposite side. The odds of clearing the stone were three times higher for those who slept stone-side down. This makes intuitive sense: gravity pulls the stone toward the ureter’s exit path. It’s a simple adjustment that costs nothing.
What About Lemon Juice and Herbal Supplements?
Lemon juice is often mentioned in kidney stone advice, and there is a real mechanism behind it. Citrate, a compound in citric acid, binds to calcium and helps prevent new stones from forming. Drinking half a cup of lemon juice concentrate diluted in water each day can increase citrate levels in your urine. However, this is primarily a prevention strategy. There is no strong evidence that lemon juice helps a stone that’s already formed move through the ureter faster.
One herbal supplement with some preliminary data is Chanca Piedra (Phyllanthus niruri), a tropical plant whose name literally translates to “stone breaker.” A small study of 56 patients with stones under 10 mm found that after 12 weeks of drinking the plant as a tea infusion, the average number of stones per patient dropped from 3.2 to 2.0. Some patients reported spontaneous stone passage between the 21st and 70th day of use. These results are interesting but come from a small, uncontrolled study, so the evidence is far from definitive.
Warning Signs That Need Immediate Attention
Most kidney stones, while painful, are not dangerous. But certain symptoms signal complications that require urgent care:
- Fever or chills: These are not normal with an uncomplicated kidney stone. They suggest a urinary tract infection behind the blockage, which can escalate to a serious kidney infection. An infected, obstructed kidney needs urgent treatment regardless of stone size.
- Inability to keep fluids down: Persistent vomiting leads to dehydration and makes it harder for the stone to pass. You may need IV fluids.
- Pain that doesn’t respond to medication: If over-the-counter or prescribed painkillers aren’t controlling the pain, the stone may be too large or too stuck to pass on its own.
- No urine output: Complete blockage of the ureter, especially if you only have one functioning kidney, can damage the kidney. Function can start to decline within two weeks of obstruction.
Any of these situations calls for a trip to the emergency room or an urgent call to your urologist. The presence of infection behind a blocked stone is the most time-sensitive scenario, because bacteria trapped in a backed-up kidney can enter the bloodstream quickly.