Kidney stone pain is one of the most intense physical experiences people report, with patients rating their worst pain at an average of 7.9 out of 10. That score is nearly identical to what first-time mothers report during labor (7 to 8 out of 10), which is why the comparison between kidney stones and childbirth comes up so often. But pain is only part of the picture. Kidney stones produce a distinct combination of sensations that can shift and change as the stone moves through your urinary tract.
Where the Pain Starts and How It Moves
The hallmark sensation is intense flank pain on one side of your body, between your lower ribs and hip. This is called renal colic, and it happens when a stone blocks the narrow tube (ureter) that connects your kidney to your bladder. The blockage causes pressure to build behind the stone, stretching the kidney and ureter wall. That pressure, not the stone scraping tissue, is the main source of the pain.
As the stone shifts position, the pain migrates. It can radiate to your back, your lower abdomen, or down into your groin. Many people describe a restless, can’t-get-comfortable quality to it. Unlike muscle pain or a pulled back, no position relieves it. You might feel a dull ache that never fully lets up, punctuated by sharp, cramping waves that last 20 to 60 minutes each. The pain typically reaches its worst point one to two hours after it begins.
Stone Size Doesn’t Predict Pain Level
One of the most counterintuitive facts about kidney stones is that a tiny stone can hurt just as much as a large one. A study published in the American Journal of Emergency Medicine found no correlation between stone size and pain scores. The researchers concluded that location within the ureter and the amount of pressure buildup matter far more than the stone’s dimensions. A 2 mm stone lodged in a tight spot can produce the same crippling pain as one twice its size.
Nausea, Vomiting, and Other Symptoms
Kidney stones don’t just cause pain in your side. The pressure and swelling in your kidney triggers nausea and vomiting in many people, which can be confusing if you don’t yet know what’s causing your symptoms. Some people initially think they have food poisoning or a stomach bug. The nausea tends to come in waves alongside the pain, driven by the same pressure buildup that’s stretching the kidney’s outer capsule.
You may also notice changes when you urinate. Blood in the urine is common and can make it look pink, red, or cola-colored. You might feel an urgent, persistent need to pee even when your bladder isn’t full, especially once the stone reaches the lower part of the ureter near the bladder. Some people experience a burning sensation during urination. These urinary symptoms can overlap with what a urinary tract infection feels like, and in fact, a stone can sometimes cause an infection by creating a blockage where bacteria thrive.
How Long the Whole Process Takes
The total time from first symptom to passing a stone depends heavily on size. About 80% of stones smaller than 4 mm pass on their own within roughly 31 days. For stones between 4 and 6 mm, the odds drop to about 60%, with an average timeline of around 45 days. Stones larger than 6 mm have only about a 20% chance of passing without intervention, and the process can take up to 12 months.
That doesn’t mean you’ll be in constant agony for weeks. The pain tends to come in episodes. You might have a brutal few hours, then feel relatively fine for days before the stone shifts again and triggers another round. Between episodes, you may feel a low-grade soreness in your flank or have no symptoms at all. The unpredictability is part of what makes the experience so stressful.
What It Feels Like When the Stone Finally Passes
For most people, there’s an unmistakable moment of relief. The pain drops away, sometimes within minutes, once the stone clears the ureter and enters the bladder. From the bladder, the stone usually passes out during urination with little additional pain, though you might feel a brief pinch or pressure. Some people hear the stone hit the toilet bowl. Others never see it at all but realize it’s gone because their pain disappears.
If your pain resolves but you never spot the stone, it’s worth following up with a doctor. In some cases, pain can temporarily improve even while the stone is still causing a partial blockage. Residual soreness in the flank area for a few days after passing a stone is normal.
Symptoms That Need Immediate Attention
Most kidney stone episodes, while painful, resolve safely. But certain symptoms signal a more dangerous situation. A fever above 101.5°F alongside kidney stone pain suggests an infection behind the blockage, which can escalate quickly. Cloudy or foul-smelling urine points in the same direction. Persistent vomiting that prevents you from keeping fluids down creates a dehydration risk. And pain that’s truly uncontrollable, meaning no position or over-the-counter medication touches it, is a reason to seek emergency care rather than wait it out.
People with only one functioning kidney, diabetes, or reduced kidney function face higher risks from a stone blockage, since a single obstructed kidney can cause damage more rapidly when there’s no healthy kidney compensating on the other side.