Kidney stones: symptoms, treatment and prevention in the UK

Kidney stones are hard crystals that form in the kidney and may pass into the ureter, where they can cause severe wave-like flank pain, nausea and blood in the urine. Small stones may pass without a procedure, but severe pain, fever, shivering or blood in urine needs urgent medical help. The best long-term prevention is not a generic "low oxalate" diet: it starts with stone analysis, enough fluid, normal dietary calcium, lower salt, and targeted treatment if stones recur.¹²

What kidney stones are

Kidney stones form when urine becomes concentrated enough for minerals and waste products to crystallise. Those crystals can grow into a stone in the kidney, move into the ureter, irritate the urinary tract or block urine flow. The pain is often not from a sharp stone scraping the kidney; it is from obstruction, pressure and spasm as the urinary tract tries to move the stone.

The commonest stones contain calcium, usually calcium oxalate or calcium phosphate. Other stones include uric acid stones, infection-related struvite stones, cystine stones from a rare inherited condition, and drug-related stones. The type matters because the prevention plan changes. A person with calcium oxalate stones and high urinary calcium needs a different plan from someone with uric acid stones, recurrent infection stones or cystinuria.

NHS guidance says waste products can form crystals that collect inside the kidneys, and risk is higher if you do not drink enough fluids, take some medicines, or have a condition that raises certain substances in urine.¹ Family history, previous stones, dehydration, hot environments, bowel disease or bowel surgery, recurrent UTIs, gout, obesity, high salt intake and some supplements or medicines can all shift the risk.

Symptoms and emergency signs

Small stones may cause no symptoms and pass unnoticed. A stone that moves into the ureter can cause classic renal colic: severe pain in the side or back that comes in waves, often moving towards the groin, with nausea, vomiting, restlessness, sweating, urinary urgency or visible blood in urine. People often cannot get comfortable.

Kidney stone pain can overlap with appendicitis, ectopic pregnancy, ovarian torsion, gallbladder disease, kidney infection, testicular problems, abdominal aortic aneurysm and severe back pain causes. That is why new severe flank or abdominal pain deserves medical assessment rather than assuming it is "just another stone". If you are pregnant, have one kidney, known kidney disease, fever, shivering, vomiting, confusion, difficulty passing urine, or uncontrolled pain, do not wait it out.

How they are diagnosed

NICE recommends urgent low-dose non-contrast CT within 24 hours for adults with suspected renal colic. Pregnant women should be offered ultrasound instead of CT, and children and young people should have urgent ultrasound first.² This is a practical balance: CT is very good at finding stones and alternative diagnoses, but ultrasound avoids radiation where that matters most.

Urine tests can check for blood, infection and pH. Blood tests may check kidney function, infection markers and calcium. NICE says to consider stone analysis for adults with ureteric or renal stones and to measure serum calcium in adults with stones.² If you pass a stone, try to catch it in a clean container or sieve and ask whether it can be sent for analysis.

People with recurrent stones, children, unusual stone types, one kidney, kidney disease, bowel disease, high calcium, suspected cystinuria or repeated infection stones may need deeper metabolic assessment. This can include 24-hour urine testing for volume, calcium, oxalate, citrate, uric acid, sodium and other markers. The point is to stop guessing. A low-oxalate diet is not the answer to every stone, and a calcium restriction can backfire.

Treatment options

Acute treatment starts with pain and nausea control, then deciding whether the stone is likely to pass or needs intervention. NICE recommends NSAIDs as first-line pain relief for suspected renal colic, intravenous paracetamol if NSAIDs are contraindicated or insufficient, and opioids only if those options are contraindicated or not giving enough relief. NICE also says not to offer antispasmodics.² NSAIDs are not suitable for everyone, especially some people with kidney disease, stomach ulcers, anticoagulants, heart failure or late pregnancy, so clinician advice matters.

Some stones pass with time, pain control and monitoring. NICE says to consider alpha blockers for distal ureteric stones less than 10 mm, noting this was an off-label use when the guideline was published.² Do not start someone else's tamsulosin or use it without advice, especially if you have low blood pressure, take blood-pressure medicines or are pregnant.

Larger stones, stones unlikely to pass, ongoing intolerable pain, infection, blocked kidney or kidney impairment may need a procedure. Options include shockwave lithotripsy, ureteroscopy and percutaneous nephrolithotomy. NICE gives size-based recommendations: for example, shockwave lithotripsy is commonly offered for renal stones under 10 mm, while renal stones larger than 20 mm, including staghorn stones, usually need percutaneous nephrolithotomy.² The right option depends on size, site, anatomy, infection risk, kidney function and local expertise.

Preventing recurrence

Prevention matters because NHS guidance estimates up to half of people who have had kidney stones will have them again within the following 5 years.¹ The first rule is dilute the urine. NICE advises adults to drink 2.5 to 3 litres of water per day, enough in practice to keep urine pale, unless a clinician has given you a fluid restriction.² A 5-year randomised trial by Borghi and colleagues found that high water intake, aiming for urine volume of at least 2 litres per day, reduced recurrence after a first idiopathic calcium stone.³

The second rule is: do not automatically cut calcium. NICE advises maintaining normal calcium intake, 700 to 1,200 mg per day for adults, while limiting salt to no more than 6 g per day.² The reason is counterintuitive. Calcium in food binds oxalate in the gut, reducing how much oxalate reaches urine. In a 5-year NEJM trial in men with recurrent calcium oxalate stones and hypercalciuria, a normal-calcium, low-animal-protein, low-salt diet protected better than a low-calcium diet.⁴

That does not mean calcium tablets are harmless. Food calcium and calcium supplements are not identical in stone risk, and high-dose supplements should be discussed if you form stones. The most practical food advice is to keep normal calcium with meals, reduce salt, avoid extreme animal-protein intakes, avoid dehydration, and tailor oxalate advice to your stone type and urine results. Spinach, rhubarb, beetroot, nuts, chocolate and tea are high-oxalate foods, but cutting them all without a diagnosis can make diet unnecessarily restrictive.

Citrate can help stop calcium stones crystallising. NICE advises adding fresh lemon juice to drinking water and considering potassium citrate for recurrent stones that are predominantly more than 50% calcium oxalate.² Potassium citrate is a medicine, not just lemon water, and it is not suitable for everyone, especially people with kidney impairment or high potassium risk. NICE also says to consider thiazides for adults with recurrent predominantly calcium oxalate stones and hypercalciuria after reducing sodium intake to 6 g daily or less; this was off-label use in 2019.²

Modern evidence reviews remain broadly consistent with that hierarchy. A 2026 AHRQ comparative review found the clearest adult dietary evidence for increased water intake and a normal-to-high calcium, low-sodium, low-animal-protein diet in selected recurrent stone formers, while pharmacological prevention depends on the metabolic abnormality and stone type.⁵ In plain English: more water and less salt are the base. Tablets come after the stone type and urine chemistry are understood.

A practical plan

During an acute attack, prioritise safety: pain control, temperature, urine flow, vomiting, pregnancy status, kidney history and whether infection is possible. Ask what imaging showed: kidney or ureter, size, position, blockage, hydronephrosis, infection signs, and whether the stone is likely to pass. If you are discharged, be clear on when to return and how follow-up will confirm the stone has passed.

After the attack, move to prevention. Keep the stone if it passes. Ask for stone analysis and serum calcium. If this is not your first stone, ask whether you need 24-hour urine testing or a urology or nephrology review. Bring a real diet and fluid history rather than saying you "drink loads". Urine colour, work conditions, exercise sweat, sleep, alcohol, salt, protein, supplements and bowel symptoms can all matter.

If kidney stones sit alongside recurrent UTIs, gout, high vitamin D intake, bariatric surgery, inflammatory bowel disease or unexplained high calcium, use the health library to map the overlap before assuming there is one cause. The start here guide can help you organise questions for a GP or urologist, while insights can help you separate evidence-based prevention from detox claims. If you are taking vitamin D, calcium, vitamin C, electrolytes, alkalinising powders or herbal products, check the plan with the stack builder before escalating doses.

This article is educational and does not constitute medical advice, diagnosis, or a treatment recommendation. Medication uses described as “off-label” are not licensed for that purpose in the UK and should only be considered under qualified clinical supervision. Always speak to your GP, pharmacist, or a registered specialist before starting, stopping, or changing any treatment. If you have severe or alarm symptoms - unintentional weight loss, blood in your stool, difficulty swallowing, persistent vomiting, a fever, or severe pain - seek urgent medical care.