Kidney Stones: Causes and How to Reduce Your Risk
- , by SANUSq Research team
- 8 min reading time
Anyone who has passed a kidney stone will tell you the pain is unforgettable — but the good news is that a few sensible habits can substantially cut your risk of another.
What kidney stones are
Kidney stones are hard deposits that form in the kidneys when certain substances in the urine — most often calcium, oxalate and uric acid — become concentrated enough to crystallise and clump together. Small stones often pass unnoticed in the urine, but a larger one can lodge in the urinary tract and cause the intense, cramping pain (renal colic) that sends people to A&E, sometimes with nausea, blood in the urine or the need for medical intervention. Kidney stone symptoms, when they appear at all, therefore tend to be that one-sided cramping pain in the back or side, nausea, blood in the urine, or difficulty passing it. They're common, and unfortunately they tend to recur, which is exactly why prevention is worth taking seriously.
Calcium oxalate stones are the most common type, and diet along with adequate hydration can meaningfully influence stone formation — low dietary calcium and high dietary sodium both raise the risk, while good fluid intake dilutes the urine and reduces the concentration of stone-forming substances (the role of diet in kidney stone prevention, 2025).
Hydration: the single most important step
If there's one thing to take away, it's this: drink more water. The most consistent, best-evidenced way to prevent kidney stones is simply to keep your urine dilute, so that stone-forming minerals stay dissolved rather than crystallising.
A meta-analysis found that higher fluid intake significantly reduced the recurrence of calcium stones, and that a low-sodium, normal-calcium diet also markedly reduced recurrence (dietary treatment and fluid intake meta-analysis, 2021).
A useful rule of thumb is to drink enough that your urine stays pale straw-coloured through the day — more in hot weather or when you're active. It's the simplest, cheapest preventive measure there is.
The counterintuitive truth about calcium
Here's the point that surprises most people: if you're prone to the common calcium-oxalate stones, cutting calcium out of your diet is usually the wrong move. Adequate dietary calcium actually binds to oxalate in the gut, so it's carried out in the stool rather than absorbed and sent to the kidneys, where it could form stones. Very low-calcium diets can therefore backfire and increase risk. The better targets are usually cutting back on salt (high sodium raises urinary calcium) and being moderate with high-oxalate foods and animal protein — while keeping calcium intake normal, ideally from food. This is a good example of why self-treating with drastic dietary cuts can do more harm than good.
Sensible dietary habits
Beyond hydration and normal calcium, a few habits help. Go easy on salt and heavily processed foods. Be moderate rather than extreme with very high-oxalate foods (such as spinach, rhubarb, nuts and beetroot) — and pairing them with a calcium-containing food can help bind the oxalate. Keep animal protein moderate, as large amounts raise stone-forming factors in the urine, and plenty of fruit and vegetables helps in the opposite direction by raising protective urinary citrate. Magnesium and citrate are both thought to help inhibit stone formation, part of the wider case for a mineral-rich, plant-forward diet we make in the benefits of magnesium and the anti-inflammatory diet.
Not all stones are the same
It's worth knowing that kidney stones come in a few types, because prevention can differ slightly depending on which you form. Calcium oxalate stones are by far the most common, and the hydration-and-diet advice here is aimed mainly at them. Uric acid stones are linked with high animal-protein intake and acidic urine, and tend to affect people with gout or metabolic syndrome; plenty of fruit and vegetables, which make the urine less acidic, particularly helps here. Less common are struvite stones (often related to certain urinary infections) and cystine stones (an inherited condition). This variety is one more reason that, after a first stone, it's genuinely useful to have a passed stone analysed if possible — knowing the type lets prevention be targeted rather than generic, which is where a doctor's input pays off.
Other things that raise the risk
Diet and fluid are the levers most within your control, but a few other factors matter. A family history of stones raises risk, as does living or working somewhere hot, where fluid losses are high and urine concentrates without your noticing. Some medical conditions and medications also increase risk, which is another reason a recurrent stone deserves proper investigation rather than dietary guesswork.
When to see a doctor
Kidney stones are a medical matter, and this article is about lowering risk, not self-treating an attack. Severe pain in the side or back, blood in the urine, fever, or difficulty passing urine all warrant prompt medical attention. Anyone who has had a stone should talk to their doctor about prevention — because stones can reflect an underlying metabolic issue, a doctor may analyse a passed stone or run tests to tailor advice, and in some cases prescribe specific treatment. Kidney stone treatment itself is strictly a medical matter: decisions about pain relief, medication or removing a stone belong with a doctor, and nothing in this article is a substitute for that. Recurrent stones in particular deserve proper investigation rather than guesswork.
Frequently asked questions
How can I prevent kidney stones?
The best-evidenced step is drinking plenty of water to keep urine dilute. Alongside that: go easy on salt, keep dietary calcium normal (not low), be moderate with high-oxalate foods and animal protein, and eat plenty of fruit and vegetables. Anyone with recurrent stones should see a doctor.
Should I avoid calcium to prevent kidney stones?
Usually no — this is a common misconception. Adequate dietary calcium binds oxalate in the gut so it isn't absorbed, which can actually lower the risk of the common calcium-oxalate stones. Very low-calcium diets can backfire. Cutting salt is generally more useful.
How much water should I drink to prevent stones?
Enough to keep your urine pale straw-coloured through the day, and more in hot weather or when active. Keeping the urine dilute stops stone-forming minerals from crystallising, and it's the simplest and most effective preventive measure.
What foods cause kidney stones?
High salt intake and large amounts of animal protein raise stone-forming factors in the urine, and very high-oxalate foods (spinach, rhubarb, nuts, beetroot) can contribute for some people. Moderation, good hydration and normal calcium intake matter more than eliminating single foods.
Are kidney stones likely to come back?
Unfortunately, they often recur, which is why prevention is so worthwhile. Good hydration and sensible diet substantially lower the odds. Because recurrent stones can reflect an underlying issue, they deserve proper medical investigation to tailor prevention.
When should I see a doctor about kidney stones?
Seek prompt medical attention for severe side or back pain, blood in the urine, fever, or difficulty passing urine. Anyone who has had a stone should discuss prevention with their doctor, who may test to find the cause and tailor advice or treatment.
References
- Ojo OA, Brown N, Yaceczko S, et al. The Role of Diet in Kidney Stone Pathogenesis and Prevention. Curr Urol Rep. 2025;26(1):74. PMID 41258546
- Wang Z, Zhang Y, Wei W. Effect of dietary treatment and fluid intake on the prevention of recurrent calcium stones and changes in urine composition: A meta-analysis and systematic review. PLoS One. 2021;16(4):e0250257. PMC8055022
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