Most kidney stones pass on their own within one to three weeks, though the exact timeline depends heavily on the stone’s size and where it’s sitting in your urinary tract. Stones smaller than 4 mm often pass in one to two weeks, while larger stones can take three weeks or more. About 94% of stones that will pass on their own do so within six weeks.
Timeline by Stone Size
Size is the single biggest factor in how long you’ll be waiting. Stones smaller than 4 mm have the easiest path out: most pass within one to two weeks. Larger stones, in the 4 to 6 mm range, typically need two to three weeks. European urology data shows that roughly 75% of stones under 5 mm pass without intervention, while about 62% of stones 5 mm and above eventually make it out on their own. The average time to expulsion across all sizes is about 17 days, with a range of 6 to 29 days.
Once a stone reaches 10 mm, spontaneous passage becomes unlikely, and most urologists will recommend a procedure rather than continued waiting.
How Location Affects Passage Time
Your urinary tract has three main zones a stone travels through: the proximal ureter (closest to the kidney), the mid-ureter, and the distal ureter (closest to the bladder). A stone near the bladder has much less distance to travel and passes faster, averaging about 21 days. A stone stuck near the kidney averages closer to 36 days.
Each millimeter of stone size adds roughly five days to the timeline. So a 3 mm stone near the bladder might pass in under two weeks, while a 6 mm stone near the kidney could take well over a month. Once the stone finally drops into the bladder itself, the hardest part is over. It typically passes out within a few days after that.
What Each Stage Feels Like
The pain from a kidney stone isn’t constant. It comes in waves as the stone moves and temporarily blocks the flow of urine. The worst pain usually hits when the stone enters the ureter, the narrow tube connecting your kidney to your bladder. This is the classic “flank pain” that radiates from your back toward your lower abdomen and groin. You may also feel nausea, notice blood in your urine, or have a frequent, urgent need to urinate.
Pain can spike for hours, then ease up for a day or two as the stone shifts position. Many people mistake a quiet period for the stone having passed, only to have another episode when it starts moving again. The pain generally shifts lower in your abdomen as the stone progresses down the ureter, which is actually a good sign. Once it reaches the bladder, most people feel significant relief. Passing the stone from the bladder through the urethra is usually quick and far less painful.
Medications That Speed Things Up
For stones 10 mm or smaller, doctors often prescribe a type of medication called an alpha-blocker. These drugs relax the smooth muscle lining the ureter, giving the stone a wider path. A large analysis of 24 clinical trials found that alpha-blockers shortened passage time by about 3.8 days on average compared to no medication. That may not sound like much, but when you’re in pain, four fewer days matters.
The American Urological Association recommends this approach for up to 30 days. After that window, a follow-up imaging scan is typically ordered to check whether the stone has moved, stayed put, or is causing a backup of urine in the kidney.
When Waiting Becomes Risky
Not every stone should be given time to pass. A stone that stays lodged in one spot can block urine flow and cause the kidney to swell, a condition called hydronephrosis. Without treatment, severe or prolonged hydronephrosis can cause lasting kidney damage and, in rare cases, kidney failure.
Intervention is needed regardless of stone size if you develop any of these:
- Fever or signs of infection. A blocked ureter plus bacteria is a urological emergency.
- Pain that doesn’t respond to medication. If over-the-counter and prescription painkillers can’t control the pain, waiting is no longer reasonable.
- Declining kidney function. This is especially urgent if you have only one functioning kidney or if both ureters are blocked.
- No progress after four to six weeks. If the stone hasn’t moved on follow-up imaging, your urologist will likely recommend a procedure.
A Realistic Expectation
If you’ve just been told you have a kidney stone, here’s the practical picture. A small stone (under 5 mm) in the lower ureter has a strong chance of passing within two weeks, especially with medication and plenty of fluids. A mid-sized stone (5 to 7 mm) higher up in the ureter could take three to five weeks and has a lower, though still reasonable, chance of passing on its own. Anything at or above 10 mm will very likely require a procedure.
During the waiting period, staying well hydrated helps keep urine flowing and can nudge the stone along. Straining your urine through a mesh cup or fine strainer is worth the hassle, because capturing the stone lets your doctor analyze its composition and recommend dietary changes to prevent the next one. About half of people who pass a kidney stone will form another within five to seven years, so knowing what yours is made of is genuinely useful information.