Herbs and Supplements for Kidney Health: Stones, UTIs and When to Stop
The supplements with the best evidence for kidney health are potassium citrate, which cut recurrent calcium stones by up to 85% in randomised trials and anchors the American Urological Association's stone-prevention guideline; cranberry, which Cochrane's 2023 review found reduces urinary tract infections by about a quarter in women with recurrent UTIs and in children; and magnesium, which lowers urinary oxalate and was part of the most effective stone-prevention trial. Vitamin B6 for oxalate stones, D-mannose for UTIs and hibiscus for blood pressure have smaller or more mixed data.
This guide has two very different readers, and the advice is opposite for each. If your kidneys are healthy and your goal is to prevent stones or repeat infections, most of what follows applies and is safe. If you have chronic kidney disease (CKD), polycystic kidney disease, one kidney, or an eGFR below 60, the rule flips: potassium, magnesium, high-dose vitamin C, creatine, protein powders and several herbs (astragalus, licorice, anything labelled 'kidney cleanse') can cause real harm because your kidneys can no longer clear them. For you this page is mostly a list of what to avoid, and every item should go through a nephrologist or renal dietitian first.
See a doctor rather than self-treating if you have flank pain with fever (an infected, obstructed kidney is an emergency), blood in the urine, a UTI with fever or back pain, foamy urine or swollen ankles, or if a blood test has ever shown raised creatinine or reduced eGFR. Kidney disease is silent until advanced; the best 'supplement' for most people is a blood-pressure check and a urine albumin test.
Quick answer
- Potassium citrate (prescription) — cut recurrent calcium stones by 85% in a 3-year RCT; AUA guideline first choice
- Cranberry — Cochrane 2023: about 26% fewer UTIs in women with recurrent infections, about half as many in children
- Magnesium — lowers urinary oxalate and raises citrate; part of the most effective stone-prevention trial
- Vitamin B6 — 40 mg/day linked to 34% fewer stones in women; lowers oxalate in rare hyperoxaluria
- Hibiscus tea — lowered systolic blood pressure by 7 mmHg in 6 weeks; blood pressure is the main kidney protector
- Avoid with CKD — potassium, magnesium, vitamin C over 500 mg, creatine, astragalus and 'kidney cleanse' products
The 10 best herbs and supplements for kidney health
Ranked by the strength of human evidence. Strong = multiple trials or a meta-analysis. Moderate = a few small trials. Preliminary = early or animal data.
Potassium citrate (for stones, prescription only)
Strong evidencePotassium citrate raises urinary citrate, which binds calcium and stops crystals forming. In Ettinger's 3-year RCT of 64 recurrent calcium-oxalate stone formers, potassium-magnesium citrate reduced new stones by 85% relative to placebo, and earlier trials of potassium citrate alone cut recurrence from about 60% to 10–20%. The AUA 2014 guideline recommends it for calcium stones with low urinary citrate and for uric acid and cystine stones. Over-the-counter potassium pills (99 mg) are a different, far smaller dose and were never tested.
- Key evidence
- Ettinger 1997 RCT (Journal of Urology); AUA 2014 stone guideline
- Studied dose
- 30–60 mEq/day potassium citrate (prescription) in 2–3 divided doses with meals, guided by a 24-hour urine test
- Best for
- Recurrent calcium, uric acid or cystine stones after a 24-hour urine shows low citrate or acidic urine
- Cautions
- Dangerous in CKD and with ACE inhibitors, ARBs, spironolactone, eplerenone, potassium-sparing diuretics and trimethoprim, which all raise potassium; high potassium can stop the heart. Needs blood potassium checks. Slow-release tablets can ulcerate the gut in people with slow transit.
The 2023 Cochrane update of 50 trials and 8,857 participants found cranberry products reduced symptomatic, culture-confirmed UTIs by 26% in women with recurrent UTIs, by 54% in children, and by 53% in people at risk after bladder procedures, but not in elderly care-home residents or people with neurogenic bladders. Proanthocyanidins (PACs) stop E. coli sticking to the bladder wall; products delivering at least 36 mg PACs a day performed best. This is prevention, not treatment.
- Key evidence
- Williams 2023 Cochrane review of 50 RCTs
- Studied dose
- Capsules standardised to 36–72 mg proanthocyanidins (PACs) daily, or 250–500 mL unsweetened juice, for 6–12 months
- Best for
- Women with 2 or more UTIs a year, children with recurrent UTIs, people facing catheterisation or bladder surgery
- Cautions
- Cranberry is oxalate-rich; high-dose tablets raised urinary oxalate in one study, so stone formers should use juice or moderate doses. Case reports of raised INR with warfarin. Sweetened juice adds sugar. Does not treat an active UTI, which needs antibiotics if there is fever or back pain.
Magnesium
Moderate evidenceMagnesium binds oxalate in the gut and inhibits calcium-oxalate crystal growth in urine. It was half of the potassium-magnesium citrate combination that cut stone recurrence by 85% in Ettinger's RCT, and a 1980 Swedish study of 55 recurrent stone formers taking 500 mg magnesium hydroxide daily for up to 4 years found 90% stayed stone-free, though without a placebo group. Low dietary magnesium is linked with higher stone risk in cohorts, and magnesium citrate also raises urinary citrate.
- Key evidence
- Ettinger 1997 RCT (as potassium-magnesium citrate); Johansson 1980 open study
- Studied dose
- 200–400 mg/day elemental magnesium as citrate or glycinate, with meals so it binds dietary oxalate
- Best for
- Calcium-oxalate stone formers with healthy kidney function, particularly with cramps or constipation
- Cautions
- Not in CKD (eGFR below 30) without a nephrologist: the kidneys cannot excrete it, and high magnesium causes weakness, low blood pressure and heart rhythm problems. Loose stools at higher doses. Separate from thyroid medication, bisphosphonates and quinolone or tetracycline antibiotics by 2 hours.
D-mannose
Moderate evidenceD-mannose coats E. coli so it cannot attach to the bladder lining. In a 2014 Croatian trial of 308 women with recurrent UTIs, 2 g daily for 6 months gave a 15% recurrence rate versus 20% on nitrofurantoin and 61% with no prophylaxis. But the 2024 MERIT trial in JAMA Internal Medicine, the largest and best designed, randomised 598 women to 2 g D-mannose or placebo for 6 months and found no difference in UTI rates (51% versus 56%). It is harmless, cheap and now uncertain.
- Key evidence
- Kranjčec 2014 RCT (positive) vs Hayward 2024 MERIT RCT (negative)
- Studied dose
- 2 g powder in water once daily for prevention; some use 1.5 g twice daily at the first sign of symptoms
- Best for
- Women with recurrent E. coli UTIs who want to try something before, or alongside, cranberry
- Cautions
- Very safe; loose stools and bloating at high doses. It is a sugar, so people with diabetes should monitor glucose above 2 g. Never rely on it during a UTI with fever, back pain or in pregnancy, which all need antibiotics.
Vitamin B6 is a cofactor for the enzyme that diverts glyoxylate away from oxalate production. In the Nurses' Health Study of 85,557 women followed for 14 years, those taking 40 mg or more of B6 daily had a 34% lower risk of kidney stones, though the same finding did not appear in men. In primary hyperoxaluria type 1, a rare genetic disease, about a third of patients respond to high-dose B6 with a 30% or greater fall in urinary oxalate. For ordinary stone formers the data are observational only.
- Key evidence
- Curhan 1999 cohort of 85,557 women (JASN); trials in primary hyperoxaluria
- Studied dose
- 25–50 mg/day pyridoxine for stone prevention; higher doses only under specialist care
- Best for
- Women with recurrent calcium-oxalate stones and high urinary oxalate on a 24-hour collection
- Cautions
- Above 100 mg/day for months causes peripheral neuropathy (numbness and tingling) that can be permanent. Reduces the effect of levodopa taken without carbidopa. Safe in pregnancy at 25–50 mg.
High blood pressure is the second biggest cause of kidney failure after diabetes, and hibiscus has solid blood-pressure data: in a 2010 Tufts RCT of 65 adults with prehypertension or mild hypertension, 3 cups of hibiscus tea daily for 6 weeks lowered systolic pressure by 7.2 mmHg versus 1.3 for placebo, and a 2015 meta-analysis of 5 trials confirmed about 7.6 mmHg. One small Thai study found hibiscus increased uric acid excretion, which may matter for uric acid stones, but direct kidney-outcome trials do not exist.
- Key evidence
- McKay 2010 RCT of 65 adults (Journal of Nutrition); 2015 meta-analysis of 5 trials
- Studied dose
- 1.25 g dried calyces (one tea bag) in 240 mL water, 3 times daily, for 6 weeks or more
- Best for
- People with borderline blood pressure who want long-term kidney protection
- Cautions
- Adds to blood-pressure medication and can drop pressure too far. May lower blood sugar and reduce chloroquine absorption. Avoid large amounts in pregnancy. Mildly diuretic, so watch potassium balance in CKD.
Omega-3 fish oil
Moderate evidenceIn a 1994 New England Journal of Medicine trial, 106 patients with IgA nephropathy taking 12 g of fish oil a day for 2 years were far less likely to reach a 50% rise in creatinine (6% versus 33% on placebo), with benefit persisting at 6 years. Later IgA trials and meta-analyses were mixed, and a 2023 analysis of 19 cohorts found higher blood omega-3 levels were associated with 8–13% lower risk of CKD. For the general population it is kidney-neutral and heart-protective, which is why it stays on the list.
- Key evidence
- Donadio 1994 RCT in IgA nephropathy (NEJM); 2023 pooled cohort analysis
- Studied dose
- 1–2 g/day EPA+DHA for general use; IgA nephropathy trials used 3–12 g/day under specialist care
- Best for
- People with IgA nephropathy (with their nephrologist), or anyone with CKD and cardiovascular risk
- Cautions
- Above 3 g/day increases bleeding risk with warfarin and antiplatelets; stop 1–2 weeks before surgery. Very high doses linked with atrial fibrillation. Safe in CKD at normal doses, which is rare for a supplement.
Astragalus is the most-studied herb in CKD, almost entirely in China. The 2014 Cochrane review of 66 trials and 4,896 participants found astragalus added to standard treatment may reduce serum creatinine and proteinuria and slightly raise creatinine clearance, but rated the evidence low quality because of small, poorly blinded trials. Most used intravenous injections or decoctions not sold in the West. It is a 'discuss with your nephrologist' option, not a self-start.
- Key evidence
- Zhang 2014 Cochrane review of 66 trials (low-quality evidence)
- Studied dose
- In trials, 9–60 g/day of dried root as decoction or injection; 500 mg–1 g extract capsules 2–3 times daily have no CKD data
- Best for
- Only under nephrologist supervision in early CKD with proteinuria
- Cautions
- Immune-stimulating; avoid with immunosuppressants, after a transplant and in autoimmune kidney disease such as lupus nephritis. May lower blood pressure and blood sugar. Buy Astragalus membranaceus only; some species contain the neurotoxin swainsonine. Not for pregnancy.
Small CKD trials suggest curcumin lowers inflammation and proteinuria: a 2011 Mexican trial of 101 patients with diabetic or lupus nephropathy found turmeric reduced proteinuria and blood urea over 2 months, and a 2022 meta-analysis of 10 trials found reductions in CRP and lipids but no change in eGFR. The catch for stone formers is oxalate: 1 g a day of turmeric powder raised urinary oxalate by about 8 mg in healthy volunteers. Use a purified curcumin extract, not spice-level powder, if stones are your concern.
- Key evidence
- 2022 meta-analysis of 10 RCTs in CKD; Tang 2008 oxalate study
- Studied dose
- 500 mg curcumin extract with piperine or a phospholipid form, 1–2 times daily with food
- Best for
- People with CKD and inflammation, with nephrologist agreement; stone formers should choose extract over powder
- Cautions
- Antiplatelet effect; caution with warfarin and before surgery. Avoid in gallstones or bile-duct obstruction. Piperine raises blood levels of many drugs. Turmeric powder adds oxalate, and some imported turmeric is lead-contaminated.
Coenzyme Q10
Preliminary evidenceCoQ10 levels fall in CKD and on dialysis, and a 2017 trial gave 65 haemodialysis patients 1,200 mg daily for 4 months, lowering a marker of oxidative stress (F2-isoprostanes) by about 25% without changing any clinical outcome. A 2019 meta-analysis of 7 small trials in CKD found modest improvements in creatinine and lipids. There is no evidence it slows kidney decline. It is safe at these doses, which is why it edges onto this list ahead of better-known 'kidney' herbs.
- Key evidence
- Rivara 2017 RCT in 65 dialysis patients; 2019 meta-analysis of 7 trials
- Studied dose
- 100–200 mg/day with a fat-containing meal; dialysis trials used up to 1,200 mg
- Best for
- People with CKD who also take statins, which lower CoQ10 further
- Cautions
- Can reduce the effect of warfarin; check INR. May lower blood pressure and blood sugar. One of the few supplements with no known kidney burden.
How to choose
- First decide which reader you are. With CKD, PKD, one kidney or an eGFR under 60, start nothing here except possibly omega-3 or CoQ10 without a nephrologist. Potassium and magnesium accumulate, vitamin C above 500 mg becomes oxalate, creatine and protein powders raise the kidney's workload, and astragalus, licorice, aristolochia-containing 'cleanse' herbs and NSAIDs all have documented kidney injuries.
- After a calcium-oxalate stone, get a 24-hour urine collection and ask about potassium citrate; it is the most effective preventive but a prescription needing blood tests. Add magnesium 200–400 mg with meals and, if urinary oxalate is high, vitamin B6 25–50 mg. Drinking enough to pass 2.5 litres of urine a day beats every supplement.
- For repeat UTIs, cranberry capsules standardised to 36 mg or more of PACs daily are the best-supported option and work for about 1 in 8 women who take them for 6 months. D-mannose 2 g daily is a very safe second choice, with the caveat that the largest trial found no effect. Neither treats an active infection with fever.
- If your blood pressure is borderline, hibiscus tea 3 cups a day is a food-level intervention with a 7 mmHg trial effect, and blood-pressure control is the most powerful kidney protector there is.
- Chanca piedra (Phyllanthus niruri, 'stone breaker') is not in our library but deserves a mention: a 2018 Brazilian trial of 56 stone formers found 12 weeks of the herb reduced urinary oxalate and uric acid in people whose levels were high, and a 2006 trial found slightly better stone clearance after lithotripsy, but no trial shows fewer stones. Promising, not proven; avoid it with diabetes or blood-pressure drugs. Ask AskMN to check a specific product against your medication list.
- For IgA nephropathy, fish oil is the one supplement with a positive outcome trial. For every other kidney disease, no supplement has been shown to slow decline; blood pressure, blood sugar, an SGLT2 inhibitor and avoiding NSAIDs are what the evidence supports.
What to skip
High-dose vitamin C
Vitamin C is metabolised to oxalate. In a 23,000-man Swedish cohort, 1,000 mg/day supplements doubled kidney-stone risk, and in CKD high doses deposit oxalate in the kidney itself. Keep vitamin C under 500 mg a day if you form stones or have CKD.
N-acetylcysteine for 'kidney protection'
NAC was supposed to prevent contrast-dye kidney injury. Two huge trials, ACT (2,308 patients, 2011) and PRESERVE (4,993 patients, 2018), found no benefit. Not harmful, but it does not protect kidneys.
'Kidney cleanse' and 'kidney detox' products
Kidneys are the detox organ; nothing cleanses them. Products in this category have contained aristolochic acid (a cause of irreversible kidney failure and urinary-tract cancer), high-dose juniper and uva-ursi (kidney irritants) and undeclared diuretics. This is the most dangerous supplement category for the kidney.
Creatine and protein powders if you have CKD
Creatine is safe for healthy kidneys at 3–5 g/day, but it raises serum creatinine, which confuses kidney tests, and in established CKD the extra nitrogen load matters. CKD protein targets are usually 0.6–0.8 g/kg, which powders blow past.
Safety and when to see a clinician
- See a clinician urgently for flank pain with fever or vomiting, blood in the urine, inability to pass urine, or a UTI with fever, shaking or back pain. An obstructed or infected kidney can cause sepsis within hours.
- With CKD, PKD, a transplant, one kidney or an eGFR under 60, run every supplement past a nephrologist or renal pharmacist. The dangerous ones are potassium, magnesium, phosphorus-containing products, vitamin C over 500 mg, creatine, aloe latex, licorice, astragalus, juniper, uva-ursi and anything from an unregulated 'cleanse'.
- Drug interactions: potassium citrate with ACE inhibitors, ARBs, spironolactone or trimethoprim can cause life-threatening hyperkalaemia; cranberry and omega-3 above 3 g/day can raise INR on warfarin; hibiscus adds to blood-pressure drugs; curcumin with piperine raises levels of many medicines.
- Avoid NSAIDs (ibuprofen, naproxen, diclofenac) if you have kidney disease, are dehydrated, or take an ACE inhibitor plus a diuretic; they are the commonest cause of drug-induced kidney injury and no herb undoes it.
- Pregnancy: UTIs in pregnancy always need antibiotics, not cranberry or D-mannose alone, because untreated infection causes preterm birth. Avoid astragalus, high-dose B6, hibiscus in quantity and medicinal curcumin; magnesium and modest cranberry are fine.
- Stone formers: do not cut dietary calcium (it binds oxalate in the gut); do limit salt, animal protein and very high-oxalate foods such as spinach, rhubarb, almonds and turmeric powder; and do not take calcium or vitamin D supplements without a 24-hour urine test.
What matters as much as any herb
- Fluids: passing at least 2–2.5 litres of urine a day halved stone recurrence in a 5-year RCT, a bigger effect than any supplement. Water is best; lemon juice adds citrate.
- Blood pressure under 130/80 and blood-sugar control are the two levers that actually slow CKD. A home blood-pressure monitor is the highest-value 'kidney supplement' money can buy.
- Salt under 5 g a day: sodium drives calcium into the urine (stones) and blood pressure up (CKD). Most of it comes from bread, processed meat and ready meals, not the shaker.
- Dietary calcium, not supplements: 1,000–1,200 mg a day from food lowered oxalate-stone recurrence by 51% versus a low-calcium diet in a 5-year RCT, because calcium binds oxalate in the gut.
- Get tested: a urine albumin-to-creatinine ratio and an eGFR blood test detect kidney disease years before symptoms. Everyone with diabetes, high blood pressure or a family history should have both yearly.
Frequently asked questions
What is the best supplement for kidney health?
For healthy kidneys, no supplement improves kidney function; the evidence-based goals are preventing stones and UTIs, and the best-supported products for those are potassium citrate (prescription) and cranberry. For existing kidney disease, no supplement slows decline, and the real question is which ones to stop.
What herbs are good for kidney stones?
Honestly, the evidence favours minerals over herbs: potassium citrate, magnesium and, for women with high oxalate, vitamin B6. Chanca piedra has two small trials showing lower urinary oxalate and better fragment clearance but none showing fewer stones. Hydration to 2.5 litres of urine a day and normal dietary calcium do more than any herb.
Does cranberry prevent UTIs?
Yes, modestly. Cochrane's 2023 review of 50 trials found about 26% fewer UTIs in women with recurrent infections and about half as many in children and after bladder procedures, but no benefit in elderly care-home residents or neurogenic bladders. Use capsules standardised to at least 36 mg proanthocyanidins; most juices contain far less.
Which supplements should I avoid with chronic kidney disease?
Potassium, magnesium and phosphate supplements accumulate; vitamin C above 500 mg becomes oxalate; creatine and protein powders add nitrogen load; aloe latex, licorice, astragalus, juniper, uva-ursi and any 'kidney cleanse' have documented harms; and NSAIDs are the commonest drug cause of kidney injury. Run anything new past your nephrologist, including vitamin D.
Is D-mannose better than cranberry for UTIs?
The evidence now favours cranberry. D-mannose had one strongly positive trial in 2014, but the much larger 2024 MERIT trial of 598 women found no difference from placebo. Cranberry has 50 trials and a consistent 26% reduction in recurrent UTIs. D-mannose is harmless, so taking both is reasonable.
Can vitamin C damage your kidneys?
At high doses, for some people, yes. Vitamin C breaks down into oxalate, and 1,000 mg/day supplements doubled kidney-stone risk in a large Swedish cohort of men. In CKD, high doses can deposit oxalate crystals in the kidney. Keep supplemental vitamin C at or below 500 mg a day if you form stones or have reduced kidney function.
Does turmeric cause kidney stones?
Turmeric powder is high in oxalate: 1 g a day raised urinary oxalate by about 8 mg in healthy volunteers, enough to matter if you already form oxalate stones. Purified curcumin extracts contain almost no oxalate, so stone formers who want curcumin should use an extract and skip spice-level powder supplements.
References
- Williams G, Hahn D, Stephens JH, Craig JC, Hodson EM. Cranberries for preventing urinary tract infections. Cochrane Database of Systematic Reviews (2023)
- Pearle MS, Goldfarb DS, Assimos DG, et al.. Medical management of kidney stones: AUA guideline. Journal of Urology (2014)
- Ettinger B, Pak CY, Citron JT, et al.. Potassium-magnesium citrate is an effective prophylaxis against recurrent calcium oxalate nephrolithiasis. Journal of Urology (1997)
- Thomas LD, Elinder CG, Tiselius HG, Wolk A, Akesson A. Ascorbic acid supplements and kidney stone incidence among men: a prospective study. JAMA Internal Medicine (2013)
- Curhan GC, Willett WC, Speizer FE, Stampfer MJ. Intake of vitamins B6 and C and the risk of kidney stones in women. Journal of the American Society of Nephrology (1999)
- Kranjčec B, Papeš D, Altarac S. D-mannose powder for prophylaxis of recurrent urinary tract infections in women: a randomized clinical trial. World Journal of Urology (2014)
- Hayward G, Mort S, Hay AD, et al.. D-Mannose for prevention of recurrent urinary tract infection among women: a randomized clinical trial. JAMA Internal Medicine (2024)
- Donadio JV Jr, Bergstralh EJ, Offord KP, Spencer DC, Holley KE. A controlled trial of fish oil in IgA nephropathy. New England Journal of Medicine (1994)
- Zhang HW, Lin ZX, Xu C, Leung C, Chan LS. Astragalus (a traditional Chinese medicine) for treating chronic kidney disease. Cochrane Database of Systematic Reviews (2014)
- Weisbord SD, Gallagher M, Jneid H, et al.. Outcomes after angiography with sodium bicarbonate and acetylcysteine (PRESERVE trial). New England Journal of Medicine (2018)
- McKay DL, Chen CY, Saltzman E, Blumberg JB. Hibiscus sabdariffa L. tea (tisane) lowers blood pressure in prehypertensive and mildly hypertensive adults. Journal of Nutrition (2010)
- Tang M, Larson-Meyer DE, Liebman M. Effect of cinnamon and turmeric on urinary oxalate excretion, plasma lipids, and plasma glucose in healthy subjects. American Journal of Clinical Nutrition (2008)
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Ask about kidney healthThis guide is educational and is not medical advice. Herbs and supplements can interact with prescription medicines and are not regulated like drugs. Talk with a clinician or pharmacist before starting anything new, especially if you are pregnant, breastfeeding, have a chronic condition, or take medication.