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Kidney Stones

Crystals that clump together in the urinary tract until they are large enough to block it. This page exists largely to correct one piece of advice that was long the standard3 and is the opposite of what the evidence shows: cutting dietary calcium makes calcium stones more likely, not less1.

Kidney & Blood Evidence-Based

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🚨 Seek emergency care for severe flank pain WITH fever or shivering. A stone blocking a kidney that then becomes infected is a surgical emergency, and it can become life-threatening within hours. Also call 911 or go to the emergency department now for pain with vomiting that stops you from keeping fluids down, for pain that painkillers do not control, for inability to pass urine at all or for stone pain if you have only one working kidney. Ordinary stone pain is severe but not usually dangerous; it is the combination with fever that changes everything.
Definition

What Are Kidney Stones?

Solid deposits that form when the urine becomes concentrated enough for dissolved minerals to crystallize, stick together and grow. Most are made mainly of calcium oxalate8. That is why the oxalate advice here is written for stone formers and nobody else. If you form calcium oxalate stones, keep high-oxalate greens but eat them with a calcium food.

The pain does not come from the stone sitting in the kidney, where stones are frequently silent for years. It comes when one moves into the ureter (the narrow tube to the bladder) and blocks it. Pressure builds behind the obstruction, and that is the pain people describe as the worst of their lives.

Stones are a recurring condition rather than a one-off event. Without a change in what drives them, up to half of people form another within 5 years8, which is why prevention rather than treatment is the whole point of this page.

💡 Key Insight: Calcium in food binds oxalate in the gut, so the two leave together in the stool rather than the oxalate being absorbed and excreted in urine. Cut the calcium and you free the oxalate. This is the mechanism behind the finding that has still not reached most kitchen tables.
Cross-section of a kidney showing a stone forming in the renal pelvis, the ureter with a stone lodged part way down causing urine to back up, and the bladder below

🥛 Dietary calcium protects

In more than 45,000 men, higher dietary calcium intake was associated with a lower risk of symptomatic stones1. The direction surprises almost everyone, including some clinicians.

💊 Supplements do not

In women, dietary calcium was again protective while supplemental calcium was associated with higher risk2. Timing is the likely explanation: food calcium meets oxalate in the gut; a pill taken apart from meals does not.

💧 Fluid is the foundation

A five-year randomized trial in first-time stone formers found that increasing urine volume cut recurrences to fewer than half, compared with no intervention4. Nothing else on this page is that cheap.

By the Numbers

Kidney Stones by the Numbers

1 in 11
people in the United States have had a kidney stone, more men than women, in national survey data from 2007 to 2010 12
Up to half
of people who have had a kidney stone form another within 5 years of the first8
12 vs 27
recurrences within 5 years among about 100 first-time stone formers in each group, with high water intake against no change4
12 vs 23
recurrences over 5 years among 60 men in each group, on a normal-calcium, low-salt, low-animal-protein diet against a low-calcium diet3
45,619
men followed for 4 years, in whom a higher dietary calcium intake went with a lower risk of kidney stones1
1 g
of vitamin C a day raised urinary oxalate in calcium stone formers within 3 days; the body converts vitamin C to oxalate, which is why stone formers are advised to avoid vitamin C supplements10
Signs & Symptoms

Symptoms of Kidney Stones

Symptoms of a kidney stone include sharp pain in the back, side, lower abdomen or groin; pink, red or brown blood in the urine; a constant need to urinate, pain while urinating or passing little or no urine; cloudy or bad-smelling urine; and nausea and vomiting15. Fever or chills with any of these needs emergency care, as the warning at the top of this page explains.

Stone Types, and Why They Matter

The dietary advice differs by stone type, which is why having a stone analyzed changes what you should actually do.

TypeRoughly how commonWhat drives itWhat changes
Calcium oxalateThe large majorityConcentrated urine, high urinary oxalate, low urinary citrate, high sodiumFluid, normal dietary calcium with meals, less salt, moderate oxalate
Calcium phosphateLess commonAlkaline urine, high urinary calciumFluid and salt still matter; alkalinizing agents may not suit, so type-specific advice is needed
Uric acidUncommonPersistently acidic urine, high urateFluid, less animal protein and treating gout where present. These can sometimes be dissolved
StruviteUncommonUrinary infection with urea-splitting bacteriaDiet does not treat these. They need urological and antibiotic management
CystineRareAn inherited transport disorderVery high fluid intake and specialist care
💡 Catch the stone and keep it. If you pass one, strain your urine and keep the stone for analysis. The type determines whether you should be reducing oxalate, reducing animal protein or doing something else entirely, and guessing wrong wastes years. Ask for a metabolic evaluation too, particularly after a second stone or a first stone in a child.
⚠️ Some conditions raise stone risk through absorption, not diet. Fat malabsorption, as in Crohn's disease, after bowel resection or after some weight-loss surgery, causes unabsorbed fat to bind calcium in the gut, which leaves oxalate free to be absorbed. This is called enteric hyperoxaluria, and in that situation the usual advice needs specialist adjustment rather than simply following this page. See also celiac disease and ulcerative colitis.
Causes

Causes of Kidney Stones

Stones form when urine carries more stone-forming minerals than it can keep dissolved; fluid and diet drive most of it, and a few medical causes need finding because diet will not fix them9.

CauseHow It Contributes to Kidney StonesWhat Helps
Not enough fluidConcentrated urine lets crystals form and grow; first-time stone formers made less urine than people without stones4, and not drinking enough is one of the main causes13Enough fluid, mainly water, to keep urine pale, spread through the day, unless a clinician has told you to limit fluid9; in a 5-⁠year trial it cut recurrences to fewer than half4
Salt, animal protein and sugarHigher sodium and sugar intakes went with more stones in women2, and more animal protein with more stones in men1Less salt and moderate animal protein with normal calcium, the diet that gave about half the recurrences of a low-calcium diet3
Too little calcium with mealsCalcium in food binds oxalate in the gut. A low-calcium diet raised urinary oxalate and led to more recurrences than a normal-calcium diet3Normal calcium from food eaten with meals; high-oxalate foods paired with a calcium food rather than cut out, as the diet section says
Supplements and some medicinesThe body converts vitamin C to oxalate, and 1 g a day raised urinary oxalate in calcium stone formers10; calcium supplements went with higher risk while food calcium did not2; antacids, diuretics and certain antibiotics can also raise the risk13Stopping vitamin C supplements if you form calcium oxalate stones and getting the vitamin from food; any calcium supplement taken with meals and cleared with your clinician; a prescriber review, never stopping a medicine yourself
Obesity and diabetesStones were more common with obesity, and obesity and diabetes were strongly associated with a history of stones12Weight management where relevant; for uric acid stones in particular, losing excess weight matters9
Medical causes and family historyAn overactive parathyroid gland raises blood calcium and can lead to calcium stones9; urinary infection causes struvite stones, and a family history or earlier stones make more stones likely13Blood calcium tests and a 24-⁠hour urine collection, as the diagnosis section describes; parathyroid surgery can prevent further stones9, and struvite stones need antibiotic and urological care
Diagnosis

How Kidney Stones Are Diagnosed

Diagnosing the stone is the easy part. Working out why it formed is the part that prevents the next one, and the part most often skipped.

TestWhat it shows
CT of the urinary tractWhether a stone is present, its size and where it sits, which decides treatment. Worth knowing: Says nothing about why it formed.
UltrasoundObstruction and larger stones, without radiation; usually first in pregnancy. Worth knowing: Misses small stones, particularly in the ureter.
Stone analysisThe stone type, which determines the entire dietary plan. Worth knowing: Requires actually catching the stone, so strain your urine.
24-⁠hour urine collectionVolume, calcium, oxalate, citrate, uric acid, sodium; the most informative test for prevention. Worth knowing: Inconvenient, and one collection may not represent a typical day.
Blood calcium and parathyroid hormoneScreens for overactive parathyroid glands, a treatable cause. Worth knowing: Easily missed if nobody thinks to check.
Kidney functionWhether repeated stones or obstruction have caused damage. Worth knowing: The chronic kidney disease guide covers kidney function in more detail.
Medication and supplement reviewSeveral medicines, and vitamin C supplements, raise stone risk. Worth knowing: Requires someone to ask; supplements in particular are rarely volunteered.
💡 Ask for the 24-⁠hour urine collection. It is the test that turns generic advice into your advice: whether your problem is low volume, high oxalate, high calcium, low citrate or high sodium. Those five point in different directions, and following the wrong one achieves nothing while feeling like effort.
Treatment Comparison

Conventional and Holistic Treatment for Kidney Stones

🌿 HOLISTIC
💊 CONVENTIONAL
🌿

Holistic / Functional Approach

Fluid, normal dietary calcium with meals, less salt, moderate animal protein

Best Randomized Evidence
A normal-calcium, low-salt, low-animal-protein diet produced roughly half the recurrence of a low-calcium diet over five years3
Cheapest Intervention
Increasing fluid to raise urine volume, which cut recurrences to fewer than half in a five-year randomized trial4
Timeline
Urine chemistry changes within days; the benefit is measured in stones not formed over years
Advantage
This is one of the few conditions on this site where dietary change has randomized trial evidence on the outcome that matters

Full Holistic Approach Includes

  • Enough fluid to keep urine pale, spread through the day and including before bed, since urine concentrates overnight.
  • Normal dietary calcium, eaten with meals, so it can bind oxalate in the gut. Not a low-calcium diet.
  • Less salt, because sodium drives calcium into the urine.
  • Moderate animal protein, which raises acid load, urinary calcium and uric acid.
  • Moderating the highest-oxalate foods if you are a calcium oxalate former, and pairing them with a calcium food rather than removing them.
  • Citrate from citrus, since citrate inhibits crystal formation.
  • Weight management where relevant; see the obesity guide.
🌿 Worth knowing: none of this passes a stone that is already stuck, and none of it dissolves calcium stones. This is prevention of the next one.
Supplement Protocol

Evidence-Based Supplements for Kidney Stones

This is a section mostly about what to stop taking.

🚨 Vitamin C supplements raise stone risk, and this is one of the better-documented supplement harms in nutrition. In a prospective study of more than 23,000 men, those taking vitamin C supplements had roughly double the rate of incident kidney stones compared with non-users over 11 years of follow-up115, and a later analysis found supplemental but not dietary vitamin C associated with higher risk in men, though not in women6. The body converts vitamin C to oxalate, and 1 g a day raised urinary oxalate in calcium stone formers10. If you form calcium oxalate stones, stop vitamin C supplements and get the vitamin from food. Note this cuts across our gout guide, where vitamin C modestly lowers urate: if you have both conditions, the stone risk wins, and it is a conversation for your clinician.
SupplementWhat it is forTypical rangeTimingNotes & cautions
Calcium, as food not a pill Binding oxalate in the gut. This is the most misunderstood item on the page. Normal dietary intake from food; do not restrict With the meal containing oxalate Supplemental calcium was associated with higher stone risk while dietary calcium was protective2, plausibly because a pill taken between meals never meets the oxalate. If a supplement is genuinely needed for bone health, take it with food and discuss it with your clinician; see osteoporosis.
Potassium citrate Raising urinary citrate, which inhibits crystal formation. Usually prescribed rather than bought, and guided by a 24-⁠hour urine result. A prescriber decision, based on your urine chemistry As prescribed Not a supplement to self-select. Potassium loading is hazardous in reduced kidney function and with several common medicines; see chronic kidney disease. Lemon juice in water is the food-level version and is much weaker.
Magnesium Sometimes used as a crystallization inhibitor. The evidence is thin and it is not a first-line measure. Only if intake from food is low, and cleared with your clinician With food Can loosen stools. Reduce or avoid in reduced kidney function, where magnesium accumulates. Do not add it while also taking potassium citrate without medical advice.
Vitamin D3 Correcting a deficiency. Not a stone treatment, and worth a conversation first. Set a daily dose with your clinician; most adults need no blood test first With a fat-containing meal Vitamin D raises calcium absorption, so discuss it with your clinician if you form calcium stones or have raised blood calcium. Avoid large intermittent doses; see osteoporosis.
🚨 What to avoid, specifically. Vitamin C supplements, for the reason above. Low-calcium diets, which are the intuitive move and the wrong one. High-dose vitamin D without discussing it first. Very high-protein or prolonged ketogenic diets, which raise urinary calcium and lower citrate. Large amounts of high-oxalate greens powders and green smoothies built on raw spinach, where the dose is far above what anyone would eat as a salad. And any product promising to dissolve stones: uric acid stones can sometimes be dissolved medically; calcium stones cannot be dissolved by anything you can buy.
💡 Where the real leverage is. Fluid, salt and eating calcium with your meals rather than avoiding it. Those three, plus getting the stone analyzed and a 24-⁠hour urine collection done, cover almost everything that reduces recurrence.
What to Expect

What to Expect Over Time

Passing a stone takes days to weeks; preventing the next one is a matter of years.

Treatment and supportive care, together
First Weeks

Most stones are small enough to pass in the urine, which can take a few weeks, with pain relief, plenty of fluid and sometimes a medicine to help the stone pass13. Catch the stone for analysis. Larger or blocking stones are broken up or removed9. The emergency signs are under When to Seek Care.

Months 1 to 3

Once the stone has passed or been removed, the stone analysis and a 24-⁠hour urine collection show what drove it9. More fluid comes first for almost everyone.

Months 3 to 12

Diet changes follow the stone type and urine results: less salt, moderate animal protein and normal calcium with meals for calcium oxalate stones3. Preventive medicine may be added for recurrent stones, sometimes for months or longer9.

Long Term

Up to half of people form another stone within 5 years8; with high water intake, recurrences in the trial were fewer and came later4.

When to Seek Care

Call 911 or go to the emergency department now for stone pain with fever, chills or shivering, which can mean a blocked, infected kidney14; for being unable to pass urine; for pain that painkillers do not control; for vomiting that stops you from keeping fluids down9; or for stone pain if you have only one working kidney. See a clinician promptly for blood in the urine or cloudy, bad-smelling urine.

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Next Steps

Preventing the Next Stone

Passing a stone takes days to weeks; preventing the next one is a matter of years. More fluid comes first for almost everyone, and cutting dietary calcium makes calcium stones more likely, not less. Further diet changes follow your stone type and urine results.

Explore Gout → Explore Chronic Kidney Disease →

References & Evidence Notes

Each numbered entry below is either a source you can follow or a note setting out what the evidence does and does not support. Both are numbered together so the markers in the text line up.

Last reviewed October 20, 2026. Supplement entries are cross-checked against the NIH National Center for Complementary and Integrative Health and the Linus Pauling Institute Micronutrient Information Center.7 This page is nutrition education, not medical advice, and it does not replace your doctor. An obstructing stone is a urological problem and diet does not treat it. The advice here is about preventing the next stone, it assumes calcium oxalate stones unless yours have been analyzed, and it is not a substitute for a metabolic evaluation. What nutrition education can do is help you understand the evidence well enough to have a better conversation with the clinician who does treat you.

  1. Curhan GC, et al. A prospective study of dietary calcium and other nutrients and the risk of symptomatic kidney stones. N Engl J Med. 1993;328(12):833-⁠838. PubMed 8441427. More than 45,000 men followed four years; higher dietary calcium intake was associated with a lower risk of symptomatic stones. Observational, and men only, but the direction has since been confirmed by a randomized trial. ↩ ↩ ↩
  2. Curhan GC, et al. Comparison of dietary calcium with supplemental calcium and other nutrients as factors affecting the risk for kidney stones in women. Ann Intern Med. 1997;126(7):497-⁠504. PubMed 9092314. Dietary calcium was associated with lower risk and supplemental calcium with higher risk, in the same population. The proposed explanation is timing: food calcium meets oxalate in the gut; a pill taken separately does not. ↩ ↩ ↩
  3. Borghi L, et al. Comparison of two diets for the prevention of recurrent stones in idiopathic hypercalciuria. N Engl J Med. 2002;346(2):77-⁠84. PubMed 11784873. 120 men randomized for five years; the normal-calcium, low-salt, low-animal-protein diet produced roughly half the recurrence of the low-calcium diet. The key trial on this page. It studied men with high urinary calcium and recurrent stones, so applying it to other groups is an extrapolation. ↩ ↩ ↩
  4. Borghi L, et al. Urinary volume, water and recurrences in idiopathic calcium nephrolithiasis: a 5-⁠year randomized prospective study. J Urol. 1996;155(3):839-⁠843. PubMed 8583588. First-time stone formers randomized to increased water intake or no specific intervention; recurrence was substantially lower in the water group over five years. ↩ ↩
  5. Thomas LDK, et al. Ascorbic acid supplements and kidney stone incidence among men: a prospective study. JAMA Intern Med. 2013;173(5):386-⁠388. PubMed 23381591. Men taking vitamin C supplements had roughly twice the rate of incident kidney stones compared with non-users. Observational, and in men, but the mechanism is well established: excess ascorbate is metabolized to oxalate. ↩
  6. Ferraro PM, et al. Total, dietary, and supplemental vitamin C intake and risk of incident kidney stones. Am J Kidney Dis. 2016;67(3):400-⁠407. PubMed 26463139. Supplemental vitamin C was associated with higher stone risk in men, though not in women, while dietary vitamin C was not associated with stones in either, which is the distinction that matters for advice: eat the orange, question the tablet. ↩
  7. National Center for Complementary and Integrative Health (NIH), nccih.nih.gov, and the Linus Pauling Institute Micronutrient Information Center, lpi.oregonstate.edu/mic. ↩
  8. On composition and recurrence: a 2016 clinical review states that calcium oxalate is the main constituent of most kidney stones, and that recurrence reaches up to 50% within the first 5 years after a first stone, PubMed 27188687. ↩
  9. On treatment and prevention: NIDDK advises catching a passed stone for analysis and a 24-⁠hour urine collection afterward, drinking enough liquid, mainly water, as the most important preventive step unless you have kidney failure, and preventive medicine chosen by stone type, sometimes for months or longer. It notes that removing an overactive parathyroid gland can prevent stones, that weight loss matters especially for uric acid stones, and that stones that block the urinary tract or cause great pain, or vomiting with dehydration, may need urgent hospital treatment, NIDDK, kidney stone treatment. ↩
  10. On vitamin C and oxalate: in 47 calcium stone formers, 1 g or 2 g of vitamin C a day for 3 days significantly raised urinary oxalate and a measure of calcium oxalate crystallization risk; a controlled feeding study found that vitamin C is converted to oxalate in the body and raised urinary oxalate at 1,000 mg twice a day in 40% of participants, stone formers and others alike, PubMed 12631089, PubMed 15987848. ↩
  11. On vitamin C supplements in Swedish men: two reviews of kidney stone prevention report that in a cohort of more than 23,000 Swedish men, taking vitamin C supplements was linked to a nearly twofold higher risk of kidney stones over 11 years of follow-up compared with not taking them (hazard ratio 1.92), PubMed 38931286, PubMed 36012979. ↩
  12. On how common stones are: in US national survey data from 2007 to 2010 covering 12,110 people, about 1 in 11 had had a kidney stone, 10.6% of men and 7.1% of women; stones were more common in people with obesity, and obesity and diabetes were strongly associated with a history of stones, PubMed 22498635. ↩
  13. On causes and first treatment: NHS guidance lists not drinking enough fluid, some medicines and medical conditions among the causes; names antacids, diuretics, aspirin, certain antibiotics and some anti-epileptic and antiretroviral medicines among those that raise the risk of recurrence, along with a family history, earlier stones and repeated urinary infections; notes that most stones are small enough to pass in the urine, which can take a few weeks, with pain relief, fluids and sometimes a medicine to help the stone pass; and states that up to half of people get stones again within 5 years, NHS, kidney stones. ↩
  14. On fever with a blocking stone: a blocked kidney that has become infected is treated as a urological emergency, and in US hospital data on more than 300,000 such admissions, delaying drainage by 2 days or more raised the odds of death by 29%, PubMed 32501124. ↩
  15. On symptoms: NIDDK lists sharp pain in the back, side, lower abdomen or groin; pink, red or brown blood in the urine; a constant need to urinate; pain while urinating; being unable to urinate or passing only a small amount; cloudy or bad-smelling urine; and, along with the pain, nausea and vomiting, fever and chills, NIDDK, kidney stone symptoms. ↩