Most kidney stones pass on their own within one to three weeks, but the timeline depends heavily on the stone’s size and location. A stone smaller than 4 mm typically passes in one to two weeks, while stones between 4 and 6 mm can take closer to three weeks or longer. Once a stone reaches the bladder, the final stretch usually takes just a few days.
How Size Affects Passage Time
Size is the single biggest factor in how long you’ll be waiting. A study tracking patients with stones allowed to pass naturally found that average passage times ranged from about 12 days for stones under 2 mm to 37 days for stones between 4 and 6 mm. That’s a threefold difference based on just a few millimeters.
Stones under 4 mm have the most predictable timelines. The vast majority pass without any procedure. As stones get closer to 5 or 6 mm, the odds of needing intervention climb, and the wait becomes less predictable. Stones larger than 6 mm rarely pass on their own and typically require a procedure to break them up or remove them.
Where the Stone Is Matters Too
A kidney stone doesn’t just drop straight out. It has to travel from the kidney through a narrow tube called the ureter, into the bladder, and then out through the urethra. The ureter is the bottleneck, and where the stone sits within it changes your odds considerably.
Stones near the bottom of the ureter, closest to the bladder, pass on their own about 75 to 79% of the time. Stones stuck higher up, near the kidney, pass spontaneously only about 48% of the time. Mid-ureter stones fall in between at around 60%. The closer a stone is to the bladder when it’s discovered, the less time you’ll likely spend waiting.
What Each Phase Feels Like
The worst pain usually hits when a stone first enters the ureter and gets stuck. This is the classic kidney stone episode: sudden, intense pain in your side or lower back that can radiate to your groin. It often comes in waves as the ureter contracts, trying to push the stone along. Nausea and vomiting are common during these flare-ups.
Pain doesn’t stay constant for the entire passage period. You may have intense episodes lasting 20 minutes to an hour, followed by stretches of relief when the stone isn’t actively moving or blocking urine flow. Some people describe days of relative comfort between painful episodes. The pain’s location can shift as the stone moves lower, migrating from the flank toward the lower abdomen and groin. Once the stone drops into the bladder, the sharp pain typically stops. Passing it from the bladder through the urethra may cause some burning or pressure, but it’s far less painful than the ureter phase.
How to Help a Stone Pass Faster
Drinking enough fluid to produce at least 2.5 liters of urine per day is the standard recommendation during stone passage. Higher urine volume keeps things flowing and helps push the stone along. For most people, that means drinking roughly 3 liters of water throughout the day, since some fluid is lost through sweat and breathing.
For stones between 5 and 10 mm, a type of medication called an alpha-blocker can significantly improve your chances. These drugs relax the smooth muscle in the ureter, widening the passage. In a large meta-analysis, patients taking an alpha-blocker passed their stones 85% of the time compared to 66% with placebo. The average time to pass was also shorter, roughly 14 days versus longer waits without the medication. For smaller stones under 5 mm, these drugs didn’t show a meaningful benefit, likely because small stones already pass at high rates on their own.
Staying physically active, rather than lying in bed, is generally encouraged. Walking and normal movement may help the stone migrate downward, though no study has pinpointed exactly how much activity speeds things up.
When Waiting Is No Longer the Right Call
Urological guidelines generally allow up to about 30 days for a stone 10 mm or smaller to pass with the help of medication. If the stone hasn’t moved by four to six weeks, it’s time to discuss a procedure.
Some situations call for faster action regardless of the timeline. A fever alongside a kidney stone can signal an infection trapped behind the blockage, which is a serious and potentially dangerous situation. Persistent vomiting that prevents you from staying hydrated, pain that doesn’t respond to medication, or a complete blockage of urine flow all warrant urgent evaluation. If you have only one functioning kidney or both ureters are blocked, the threshold for intervention is much lower.
What Happens If a Stone Won’t Pass
When a stone is too large or too stubborn to pass naturally, the two most common procedures are shock wave therapy and a scope-based approach. Shock wave therapy uses sound waves from outside the body to break the stone into smaller fragments that can then pass on their own over the following days to weeks. The scope-based approach involves a thin instrument passed through the urethra and bladder into the ureter, where the stone is either grabbed or broken apart with a laser.
Recovery from either procedure is typically quick. Most people return to normal activities within a few days, though some soreness and blood in the urine are normal in the short term. A small temporary tube called a stent is sometimes placed in the ureter after the procedure to keep it open while swelling goes down, usually removed within a week or two.
Why Some People Pass Stones Faster Than Others
Beyond size and location, individual anatomy plays a role. People with naturally wider ureters tend to pass stones more easily. Prior stone passage can also make subsequent episodes faster, possibly because the ureter has been stretched before. Stone composition matters too: smooth, round stones move more easily than jagged or irregularly shaped ones, which can catch on the ureter walls.
Men generally have a slightly harder time with the final phase of passage because the urethra is longer, but the ureter phase, where most of the pain and delay occurs, is similar between sexes. Hydration habits, body size, and even the amount of physical activity you’re getting during the passage period all contribute to individual variation. Two people with identically sized stones can have very different experiences.