Most small kidney stones pass on their own, but the process can take anywhere from a few days to several weeks depending on the stone’s size. Stones smaller than 4mm pass naturally about 80% of the time, averaging around 31 days. Stones between 4mm and 6mm can take 45 days or longer. The good news: there are several evidence-backed strategies that can shorten that timeline and reduce pain along the way.
Drink 2 to 3 Liters of Water Daily
Fluid intake is the single most important thing you can control. Water increases urine volume, which pushes the stone through the ureter (the narrow tube connecting each kidney to the bladder). The NHS recommends drinking up to 3 liters of fluid per day, which works out to roughly 12 eight-ounce glasses. Spread this out over the entire day rather than drinking large amounts at once, and keep a water bottle nearby overnight since stones often cause flare-ups at night.
You’ll know you’re drinking enough when your urine stays pale yellow or nearly clear. Dark urine means you need more fluid. Water is ideal, but other non-sugary beverages count too.
Add Lemon Juice to Your Water
Lemon juice contains citric acid, and citrate (a salt in citric acid) binds to calcium and helps block stone formation. While this won’t dissolve a stone that’s already formed, it can prevent small fragments from clumping into something larger and may help the chemical environment in your urinary tract stay more favorable for passage. Harvard Health recommends drinking half a cup of lemon juice concentrate diluted in water each day, or the juice of two lemons, to meaningfully increase urinary citrate levels.
Use Anti-Inflammatory Pain Relief
Kidney stone pain comes from the ureter spasming around the stone, and managing that inflammation does more than just reduce discomfort. It can also reduce swelling in the ureter wall, giving the stone more room to move. A large meta-analysis covering nearly 2,000 patients found that NSAIDs (like ibuprofen) worked at least as well as opioids for acute kidney stone pain at 30 minutes after treatment. Patients who took NSAIDs also vomited less often and needed fewer rescue pain treatments compared to those given opioids.
Over-the-counter ibuprofen or naproxen is a reasonable first choice. If you have kidney disease, stomach ulcers, or are on blood thinners, check with your doctor first since NSAIDs can worsen those conditions.
Ask About Alpha-Blocker Medication
For stones up to 10mm in the lower ureter, the American Urological Association recommends a class of prescription medication called alpha-blockers, typically given for about 30 days. These drugs work by relaxing the smooth muscle lining the ureter, widening the passage so the stone can move through more easily. They’ve been shown to increase the likelihood of passing a stone without surgery, reduce pain episodes, and result in fewer emergency room visits.
This is something your doctor prescribes after confirming the stone’s size and location, usually with a CT scan. If your stone is in the distal (lower) ureter and under 10mm, this medication is considered a standard part of treatment, not an unusual request. Don’t hesitate to ask about it.
Stay Physically Active
Movement helps. Gravity and the physical jostling of activity can assist a stone in working its way down the ureter. Urologists specifically recommend activities like bicycling and jumping jacks to help dislodge stones. Walking is also beneficial and more manageable when you’re in pain. The key is to avoid staying sedentary for long stretches. Even short walks throughout the day are better than lying in bed, though you should obviously rest during acute pain flare-ups.
What Size Stones Can You Actually Pass?
Size is the biggest factor in whether a stone will pass on its own or require a procedure. Here’s a general breakdown:
- Under 4mm: These pass naturally about 80% of the time, typically within a month with adequate hydration.
- 4mm to 6mm: These often require medical management (like alpha-blockers) and can take 45 days or longer.
- 6mm to 10mm: Passage is possible, especially with medication, but the odds decrease as size increases. Your doctor may recommend a trial of passage for up to 30 days before considering a procedure.
- Over 10mm: Spontaneous passage is unlikely. Surgical options like shock wave therapy or a scope-based procedure are typically recommended.
If you don’t know your stone’s size, imaging is important. A stone that seems manageable based on pain level could still be too large to pass safely.
Warning Signs That Need Immediate Attention
Most kidney stones are painful but not dangerous. However, a stone that blocks urine flow completely or causes infection can become a medical emergency. Get care right away if you experience:
- Pain so severe you can’t sit still or find any comfortable position
- Fever or chills along with stone pain (this suggests infection)
- Nausea and vomiting that prevent you from keeping fluids down
- Blood in your urine
- Difficulty passing urine or a complete stop in urine output
A fever combined with a blocked ureter is particularly serious because infected urine trapped behind a stone can lead to sepsis. This situation requires urgent drainage, not a wait-and-see approach.
A Realistic Timeline
Even with perfect hydration, medication, and activity, passing a kidney stone is not an overnight process. For a small stone, expect at least a week or two of discomfort, with intermittent sharp flare-ups as the stone moves. The pain typically shifts from your back and side down toward your groin as the stone progresses through the ureter. Once it drops into the bladder, the worst is over. Passing it from the bladder out of the body usually causes little to no pain.
Strain your urine through a fine mesh or coffee filter so you can catch the stone when it passes. Your doctor can analyze its composition, and knowing whether it’s calcium-based, uric acid, or another type directly shapes what you should change in your diet to prevent the next one.