Most kidney stones smaller than 5 mm will pass on their own with enough fluids, good pain control, and time. Stones 4 mm or smaller pass about 98% of the time without any procedure, while 5 mm stones pass roughly 65% of the time. Once a stone reaches 6 mm or larger, the odds drop sharply, and medical intervention usually becomes necessary.
How long you’ll be waiting depends on where the stone is sitting in your urinary tract. Stones already in the lower part of the ureter (the tube connecting your kidney to your bladder) typically pass within about four weeks. Stones still in the upper ureter can take up to two months. Knowing your stone’s size and location, which your doctor can determine with a CT scan, gives you a realistic timeline.
How Much Water You Actually Need
Fluid intake is the single most controllable factor in helping a stone move. The goal is to produce at least 2 to 2.5 liters of urine per day, which generally means drinking 2.5 to 3 liters of fluid. That’s roughly 10 to 12 glasses. You want your urine to stay pale yellow or nearly clear throughout the day. If it looks dark, you’re not drinking enough.
The evidence behind this is solid. In a five-year randomized trial, people who increased their water intake to produce about 2.6 liters of urine daily had dramatically fewer stone recurrences than people who drank normally and produced only about 1 liter per day. A large UK study of over 439,000 people found that those drinking 13 or more glasses of fluid daily had a 50% lower risk of forming stones compared to those drinking six glasses or fewer. Water is the best choice, but beverages high in citric acid, like lemon juice and lime juice, can also be helpful because citrate interferes with stone crystal formation.
Pain Relief That Actually Works
Kidney stone pain comes from your ureter squeezing and swelling around the stone, not from the stone cutting tissue. Anti-inflammatory painkillers like ibuprofen and naproxen work directly on the swelling that causes pain, which is why they outperform stronger options for this specific type of pain. A large Cochrane review found that people given anti-inflammatories were 25% less likely to need additional rescue medication compared to those given opioid painkillers. Opioids also caused significantly more vomiting, which is the last thing you need when you’re trying to stay hydrated.
Over-the-counter ibuprofen or naproxen is a reasonable first step, taken with food. If that’s not enough to keep the pain manageable, your doctor can prescribe stronger anti-inflammatory options. A heating pad on your back or side can also help with muscle spasms around the ureter.
Do Alpha-Blockers Help?
You may have heard that a medication called tamsulosin (originally designed for enlarged prostates) can relax the ureter and help stones pass faster. This was widely prescribed for years, but a rigorous randomized trial found that tamsulosin produced a 50% stone passage rate compared to 47% with a placebo, a difference so small it was statistically meaningless. Some doctors still prescribe it for larger stones (5 to 10 mm) in the lower ureter, where the benefit may be more plausible, but for most stones, the evidence doesn’t strongly support it.
Stone Size and Your Odds
Size is the biggest predictor of whether a stone will pass without a procedure. Here’s what a study tracking nearly 400 stones found over 20 weeks:
- Under 3 mm: 98% pass on their own
- About 4 mm: 81% pass on their own
- About 5 mm: 65% pass on their own
- 6 mm: 33% pass on their own
- 6.5 mm or larger: only 9% pass on their own
If your stone is 6 mm or larger, waiting it out is generally not recommended. Stones that size stuck in the upper ureter are especially unlikely to pass and may need treatment within the first month to protect your kidney.
Movement and Physical Activity
Staying active can help. Walking and gentle movement use gravity and the natural jostling of your body to encourage a stone to migrate downward through the ureter. There’s no need to do anything extreme. Researchers have demonstrated that vibration and mechanical forces can dislodge small stones from the kidney, and one team at the University of Washington developed an ultrasound-based system that non-invasively pushes stones out of the kidneys. The principle is simple: motion helps, and lying in bed all day doesn’t. Walk as much as your pain allows.
Herbal Remedies
Chanca Piedra (“stone breaker”) is the most commonly discussed herbal option. It’s a tropical plant traditionally used in South America for kidney stones. One clinical study of 56 patients with stones under 10 mm found a decrease in stone size and reduced levels of problematic urinary compounds. Another study found that very small stones (under 3 mm) in the upper kidney were expelled, and stones of 3 to 4 mm shrank, but larger stones weren’t affected. A systematic review and meta-analysis, however, concluded that the clinical evidence supporting its effectiveness in reducing stone size remains limited. It appears safe, but it’s not a substitute for hydration and proper medical monitoring.
When Waiting Becomes Dangerous
Most stones are painful but not dangerous. A few situations change that equation and require urgent medical care:
- Fever with a kidney stone: This suggests infection behind the blockage, which can escalate to sepsis. Both the American Urological Association and European Association of Urology classify this as an emergency requiring immediate drainage of the kidney.
- Pain that won’t respond to any medication: Uncontrollable pain is an indication for stone removal, not just stronger painkillers.
- Decreased kidney function: If you have only one kidney, or if both ureters are blocked, waiting is not safe.
- No progress after a reasonable window: For lower ureteral stones, four weeks is a reasonable trial period. For upper ureteral stones, about two months. Beyond that, the risk of kidney damage increases.
If your stone does need a procedure, the two most common options are shock wave lithotripsy, which uses focused sound waves to break the stone into smaller fragments from outside your body, and ureteroscopy, where a thin scope is passed through your bladder to grab or laser the stone directly. Both are outpatient procedures with short recovery times.