Most small kidney stones pass on their own: Cleveland Clinic puts the figure at around 90% for stones under 6 mm, usually within one to three weeks. While you wait, the things that help are drinking enough water, pain relief your doctor approves, sometimes a prescribed tablet that relaxes the ureter, and catching the stone so it can be tested.
What you shouldn’t do is sit it out at home with fever, vomiting you can’t stop, or very little urine. Those need a hospital the same day. Here’s how to tell the difference, and how to lower the odds of another stone.
Will my stone pass on its own?
Size is the biggest factor, followed by where the stone sits. Your scan report (usually an ultrasound or a CT KUB) will give the size in millimetres and its position, for example “6 mm calculus in the right lower ureter”.
According to Cleveland Clinic:
| What your report says | What to expect |
|---|---|
| Stone smaller than 4 mm | May pass within 1 to 2 weeks |
| Stone smaller than 6 mm | Around 90% pass on their own |
| Stone larger than 6 mm | Around 60% pass on their own |
| Larger stones | Can take about 2 to 3 weeks to pass completely |
Cleveland Clinic advises following up with your doctor if a stone hasn’t passed within four to six weeks. If you’d like to understand why stones form in the first place, our article on causes and symptoms of kidney stones covers that.
Drink enough to keep your urine pale
The US National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) says drinking plenty of liquids helps move a stone along, and water is best. There’s no need to force down huge amounts at once; steady drinking through the day is the aim.
- Sip water regularly from morning to night, and keep a bottle at your desk or in your bag.
- Your urine should be pale yellow, not dark.
- Drink more on hot days, after exercise, and if you work outdoors or in a hot kitchen.
- Limit cola, very sweet drinks and alcohol.
If you have heart failure, kidney failure or have been told to restrict fluids, ask your doctor how much to drink. More water isn’t safe for everyone.
Managing the pain
Stone pain (renal colic) is a sharp pain in the back, side, lower belly or groin that may be constant or come and go. The European Association of Urology’s guideline names a non-steroidal anti-inflammatory (NSAID) as the first choice of painkiller for stone pain, depending on heart risk and side effects. Stronger medicines are a second option in hospital.
- Take only what your doctor prescribes or the pack leaflet allows. NSAIDs aren’t suitable if you have kidney disease, stomach ulcers, are pregnant, or take blood thinners, so check first.
If the pain isn’t controlled by the medicines you’ve been given, go back. The EAU says pain that doesn’t respond to painkillers is a reason to drain the kidney or remove the stone.
Medical expulsive therapy: the tablet that can help
For a stone stuck in the lower part of the ureter, your doctor may prescribe an alpha-blocker such as tamsulosin. These relax the muscle of the ureter so the stone can slip through. The EAU recommends offering alpha-blockers as one option for ureteral stones larger than 5 mm, with recent studies showing the most benefit for stones between 5 and 10 mm. This is an off-label use, so only take it on prescription, and ask your doctor about side effects such as dizziness when standing up.
Catch the stone if you can
Knowing what your stone is made of is the single most useful step for preventing the next one. MedlinePlus says you may be asked to collect your urine and strain it to catch the stone. A tea strainer kept only for this purpose, or a strainer from the pharmacy, works. Rinse the stone, let it dry, keep it in a clean container and take it to your doctor for stone analysis.
What doesn’t help, or might harm
- Beer “to flush it out”. It isn’t a treatment, and the EAU’s stone-prevention advice is to cut down on alcoholic drinks, not add them. Plain water does the flushing.
- Daily painkillers without a doctor. Repeated NSAIDs can strain the kidneys, the very organ you’re trying to protect.
- Waiting months. If the stone hasn’t passed within four to six weeks, go back to your doctor rather than carrying on at home.
- Unproven remedies. Kulthi (horse gram) water, banana stem juice and herbal “stone-breaking” mixes are popular, but they aren’t a substitute for a scan and follow-up.
When to see a doctor: red flags
The NIDDK lists symptoms that should be seen by a health care professional right away. Go to hospital the same day, or call 112, if you have:
- Fever or chills with stone pain. The EAU calls an obstructed kidney with signs of infection a urological emergency that may need urgent drainage.
- Very little or no urine, which can mean both sides are blocked
- A single kidney (from birth, surgery or a transplant) and any stone symptoms
- Pain you can’t control with the medicines you’ve been given
- Vomiting so that you can’t keep fluids or tablets down
- Cloudy or foul-smelling urine, burning when you pass urine, or blood in the urine
Our guide to early signs of kidney failure lists symptoms that mean your kidneys need checking.
Preventing the next stone, by stone type
Fluids come first. The EAU’s general advice is 2.5 to 3 litres of fluid a day, mainly water, aiming for 2 to 2.5 litres of urine. It also advises a balanced diet rich in vegetables and fibre, normal calcium intake, limited salt and animal protein, and a healthy weight. Beyond that, the NIDDK’s diet advice depends on stone type:
- Calcium oxalate (the most common type): don’t cut out calcium; get it from food such as milk, curd and paneer. Reduce salt, including namkeen, papad and pickles. If your doctor advises it, limit high-oxalate foods such as spinach, nuts, peanuts and wheat bran. For more on one common question, see our article on beetroot and kidney stones.
- Calcium phosphate: reduce salt and animal protein, and get calcium from food.
- Uric acid: limit animal protein such as red meat, organ meat, eggs and seafood, and lose weight if you’re overweight. Your doctor may prescribe medicine to make urine less acidic.
- Cystine: drinking enough water is the most important step, usually alongside specialist care.
Frequently asked questions
How big a kidney stone can pass naturally?
Most stones under 6 mm pass on their own. Larger stones can pass too, but less often. Your doctor will decide based on size, position and symptoms.
Does lemon water dissolve kidney stones?
Don’t count on it. Plain water helps a stone pass and lowers the chance of new ones. According to the EAU, the stones that can sometimes be dissolved are uric acid stones, using prescribed medicine that makes urine less acidic.
Should I strain my urine?
Yes, if your doctor asks. Catching the stone lets a lab test it, which guides how to prevent the next one.
Can I go to work while passing a stone?
Many people can, if pain is controlled and they can drink regularly. Keep water with you and know where the nearest hospital is in case red-flag symptoms start.
What if the stone doesn’t pass?
Your urologist may suggest shock wave lithotripsy, ureteroscopy (a thin scope passed up through the urethra) or, for bigger kidney stones, keyhole surgery through the back (PCNL).
This article is for general information and is not a substitute for advice from a doctor. If you have symptoms or a health condition, please consult a qualified healthcare professional.
