Most kidney stones pass on their own with a combination of fluids, pain control, and time. Stones smaller than 4 mm have about a 78% chance of passing naturally, typically within one to two weeks. What you do during that window can make a real difference in how quickly the stone moves and how much pain you experience along the way.
Size Determines Whether a Stone Can Pass
Before anything else, the single biggest factor is how large the stone is. Research using CT imaging found these spontaneous passage rates: stones 1 to 4 mm passed 78% of the time, stones 5 to 7 mm passed about 60% of the time, and stones 8 mm or larger dropped to 39%. No stones larger than 10 mm passed on their own in that study. A stone under 4 mm may clear in one to two weeks. Larger stones can take two to three weeks, and once a stone reaches the bladder, it usually passes within a few days.
If your stone hasn’t passed within four to six weeks, that’s the point where your doctor will likely recommend a procedure. Current urology guidelines say stones up to 10 mm in the lower ureter can be given roughly 30 days to pass with medication support before surgical options are considered.
Drink Enough Fluid to Keep Urine Flowing
Staying well-hydrated is the most consistently recommended strategy. The goal is to produce enough urine volume that the stone keeps moving through the ureter rather than sitting in one spot. The NHS recommends aiming for up to 3 liters (about 100 ounces) of fluid per day. Water is the best choice. You don’t need to drink it all at once, just spread it throughout the day so your urine stays pale and dilute.
Adding citrus can help, too. Drinking half a cup of lemon juice concentrate diluted in water each day, or the juice of two lemons, increases citrate levels in urine. Citrate binds to calcium and can reduce the formation of new stones while you’re trying to pass the current one.
Managing the Pain
Kidney stone pain can be severe, and controlling it matters for more than just comfort. When pain is managed well, you can stay hydrated, stay mobile, and let the stone do its work. Anti-inflammatory pain relievers like ibuprofen are the preferred first-line option. A large meta-analysis found that NSAIDs provide the most sustained pain relief compared to opioids or acetaminophen, with fewer side effects. People taking NSAIDs were less likely to vomit and needed fewer doses of backup pain medication.
Opioids work about equally well for the initial spike of pain at the 30-minute mark, but they come with more nausea and are less effective over time. Acetaminophen is another option, though people taking it also tended to need additional pain relief more often than those on anti-inflammatories.
Heat can help, too. Placing a heating pad or hot water bottle on your lower back or side where the pain is worst relaxes the surrounding muscles and can ease the cramping sensation that comes in waves as the stone moves.
Alpha-Blocker Medications
Your doctor may prescribe an alpha-blocker, a type of medication that relaxes the smooth muscle lining the ureter to give the stone more room to pass. Current American Urological Association guidelines recommend offering this medication for stones up to 10 mm in the ureter, typically for about 30 days. The evidence on how well it works is mixed. At least one well-designed trial found no improvement in passage rates or time to expulsion compared to placebo, while other studies have shown modest benefits, particularly for larger stones in the 5 to 10 mm range. It’s worth discussing with your doctor, especially if your stone is on the bigger side of what can pass naturally.
Keep Moving
Gentle physical activity can help a stone migrate through the ureter. Walking for 30 to 60 minutes a day is the most commonly suggested exercise, since the combination of gravity and body movement may nudge the stone along. Light stretching, yoga, and low-impact cycling are also considered safe. You don’t need to push through intense exercise, and if a workout significantly increases your pain, scale back. The point is to stay upright and moving rather than lying still all day.
Cut Back on Salt
High sodium intake makes your kidneys excrete more calcium into your urine, which can worsen conditions in the urinary tract while you’re trying to pass a stone. The effect is significant: every extra 6 grams of salt per day can increase urinary calcium by about 40 mg in most people, and that number doubles in people who are prone to forming stones. Reducing salt intake by even a moderate amount has been shown to lower urinary calcium within just a few days. While you’re passing a stone, keeping sodium low reduces the calcium concentration your stone has to travel through and helps prevent new stones from forming behind it.
Signs a Stone Won’t Pass Safely
Most stones pass without complications, but certain situations require urgent medical attention. A fever combined with a kidney stone suggests infection behind the blockage, and current guidelines call that a reason for emergency drainage of the kidney. Persistent vomiting that prevents you from keeping fluids down can lead to dehydration and stall the process entirely. Pain that becomes unmanageable despite medication, or complete inability to urinate, also warrants a trip to the emergency room.
If your stone is between 5 and 10 mm, you and your doctor are essentially watching and waiting. Stones in that range pass more than half the time, but the odds are lower than with smaller stones, and the timeline is longer. Knowing the size of your stone from imaging gives you the clearest picture of what to expect and when to shift from patience to intervention.