The most telling sign you’re passing a kidney stone is intense pain in your side or lower back that comes in waves, often accompanied by blood in your urine. The pain typically starts suddenly, shifts location as the stone moves, and can radiate to your groin or lower abdomen. If you’re experiencing this combination of symptoms, a stone is one of the most likely explanations.
Where the Pain Starts and How It Moves
Kidney stone pain, called renal colic, begins as intense flank pain between your lower ribs and hip on the affected side. As the stone travels down the ureter (the narrow tube connecting your kidney to your bladder), the pain shifts. It can radiate to your back, groin, or lower abdomen, and the location of your pain roughly tracks where the stone currently sits.
The pain often comes in waves lasting 20 to 60 minutes. Between waves, you might feel a dull, constant ache, then get hit with sharp, severe pain that makes it impossible to sit still or find a comfortable position. Many people describe it as the worst pain they’ve ever felt. This restlessness is actually a useful clue: with most abdominal problems, lying still helps. With kidney stones, nothing does.
When the stone finally reaches the lower part of the ureter, near where it connects to the bladder, the pain often shifts more toward the groin and you may feel a strong, persistent urge to urinate. Once the stone drops into the bladder, many people experience a sudden, dramatic relief of pain. The stone still needs to pass out through the urethra, but that final stretch is wider and usually much less painful.
Changes in Your Urine
Blood in your urine is one of the most common signs of a kidney stone. It can look pink, red, or dark like cola, depending on how much blood is present. Sometimes the blood is only visible under a microscope, so your urine might look normal even while a stone is actively moving. But if you’re having flank pain and notice any color change in your urine, that’s a strong signal.
You may also feel a burning sensation when you urinate, need to go more frequently, or feel like you can’t fully empty your bladder. These symptoms overlap with a urinary tract infection, which makes sense: a stone can irritate the lining of the ureter and bladder in similar ways. If your urine becomes cloudy or foul-smelling, that could indicate an actual infection has developed alongside the stone.
Nausea, Vomiting, and Other Body-Wide Symptoms
When a kidney stone gets stuck in the ureter, it blocks urine flow. This causes the kidney to swell and the ureter to spasm, which triggers nausea and vomiting in many people. These aren’t just side effects of severe pain (though pain alone can cause nausea). The kidney and digestive system share nerve pathways, so a distressed kidney can directly upset your stomach.
Sweating and a general feeling of being unwell are also common during an active stone episode. If you develop a fever, chills, or feel shivery, that’s a different situation. Those symptoms suggest the stone has caused a kidney infection, which happens when blocked urine allows bacteria to build up. A fever during a stone episode needs prompt medical attention.
How Long It Takes to Pass
Stone size is the biggest factor in whether you’ll pass it on your own and how long it will take. Stones smaller than 4 millimeters (roughly the size of a grain of rice) pass on their own about 78% of the time. Stones between 5 and 7 millimeters still pass without intervention about 60% of the time. Once a stone reaches 8 millimeters or larger, the odds drop to around 39%.
Most small stones take a few days to a few weeks to pass completely. The timeline varies depending on where the stone is when symptoms start, how much fluid you’re drinking, and your individual anatomy. During this period, the pain can come and go. You might have a terrible day, feel fine the next morning, and then get hit again. This stop-and-start pattern is normal and reflects the stone moving, getting temporarily stuck, and moving again.
How to Catch the Stone
Your doctor will likely ask you to strain your urine so the stone can be analyzed. This tells you what type of stone you’re forming and helps guide prevention. The process is straightforward: urinate into a collection container or toilet insert, pour the urine through a fine mesh filter (your doctor’s office or a lab can provide one), and check the filter carefully after each use.
Kidney stones can be surprisingly small. Some look like a grain of sand or a tiny piece of gravel, so check the filter closely. Be especially careful with your first morning urine, since stones often move into the bladder overnight while you’re lying down. If you find something, place it on a tissue and let it air dry completely at room temperature for 24 hours before putting it in the dry container provided. Don’t put the stone in any liquid, don’t tape it to anything, and don’t send the filter itself to the lab. Any moisture or adhesive can interfere with the analysis.
Signs That Need Immediate Attention
Most kidney stones, while painful, pass without complications. But certain symptoms mean you should get medical care right away rather than waiting it out. A fever or chills during a stone episode suggests an infection, which can become serious quickly if a blocked ureter traps infected urine. Feeling hot and cold, shivery, or unusually weak and tired alongside stone pain are warning signs of the same problem.
If you completely lose the ability to urinate, that means the stone is fully blocking your ureter and urine has nowhere to go. Pain so severe that you can’t sit still, can’t keep fluids down due to vomiting, or that doesn’t respond at all to over-the-counter pain relief also warrants a visit. In these situations, doctors may need to help the stone along rather than letting it pass naturally.