Turmeric and oxalates: Kidney stone risk

Turmeric does contain high levels of oxalates, and when consumed in supplement-level amounts, its oxalate can significantly increase urinary oxalate excretion. This is especially significant for people with a history of calcium oxalate stones, hyperoxaluria (high oxalate levels in the urine), conditions that impair intestinal absorption, or who consume large amounts of turmeric daily. In a small human study, 2.8 grams of turmeric per day provided approximately 55 mg of oxalate and increased urinary excretion after four weeks. [1]

However, the normal culinary use of turmeric should not be considered a problem for every healthy person. Modern stone prevention recommendations generally depart from the idea of a strict low-oxalate diet for everyone. It makes sense to primarily limit truly concentrated sources for people with calcium oxalate stones and elevated urinary oxalate, while simultaneously maintaining a normal calcium intake from food and adequate fluid intake. [2]

The main practical difficulty lies with dietary supplements. An analysis of commercial products published in 2026 showed a very wide range of oxalate content in turmeric supplements. Therefore, the name "curcumin," the percentage of curcuminoids, or the number of milligrams of extract do not allow one to reliably determine the oxalate load from the label. [3]

Finally, there are isolated reports of severe kidney damage associated with long-term use of large amounts of turmeric. These reports do not necessarily indicate that turmeric is generally harmful to the kidneys: the most well-documented case involved chronic diarrhea and long-term antibiotic therapy—additional factors contributing to hyperoxaluria. However, this case illustrates why daily gram doses of the supplement cannot be considered simply equivalent to a pinch of the spice. [4]

What are oxalates and why are they associated with stones?

Oxalate is an end product of certain metabolic processes in the body, also found in plant foods. Humans are unable to further break down oxalate, so the absorbed portion is primarily excreted by the kidneys. In urine, oxalate can combine with calcium to form calcium oxalate crystals. Calcium oxalate stones are the most common type of kidney stone. [5]

However, the presence of oxalate in food does not necessarily mean stone formation. Risk is simultaneously influenced by urine volume, calcium and oxalate concentrations, citrate and magnesium levels, the amount of sodium in the diet, urine acidity, bowel disease, and individual metabolic characteristics. Therefore, two people consuming the same amount of oxalate may have completely different risks of stone formation. [6]

For this reason, modern recommendations are increasingly reducing calcium oxalate stone prevention to a list of "prohibited foods." It is far more important to understand whether a person truly has elevated urinary oxalate and what other risk factors are present. For people with recurrent stones or a high risk of recurrence, modern recommendations call for a 24-hour urine test, including oxalate, calcium, citrate, sodium, and volume. [7]

How much oxalate is in turmeric?

In the most frequently cited analytical study, the total oxalate content of the turmeric used was approximately 1969 mg per 100 g, or approximately 19.7 mg per gram. Of this, approximately 1788 mg per 100 g was in water-soluble form. In other words, approximately 91% of the oxalate in turmeric was soluble. [8]

This proportion is particularly important. The total mass of oxalate in a product does not fully determine its absorption into the body: soluble forms are more readily available for intestinal absorption. In the same study, cinnamon contained a nearly comparable amount of total oxalate, but only about 6% was in soluble form. As a result, it was turmeric, not cinnamon, that significantly increased oxalate excretion in the urine. [9]

However, it's impossible to claim that all turmeric contains exactly 19.7 mg of oxalate per gram. Plant materials vary in origin, cultivation, and processing, while commercial supplements also differ in production technology and composition. The value from the study is useful as an order of magnitude indicator, not as a universal table for every product.

What the human study showed

Direct studies of turmeric and oxalate in humans are surprisingly few. The most informative study was published back in 2008 and included just 11 healthy volunteers aged 21-38 years. It was a randomized, crossover study lasting eight weeks. [10]

Participants received either approximately 3 grams of cinnamon or 2.8 grams of turmeric daily for four weeks. In both cases, the total oxalate intake was approximately 55 mg per day. The researchers also conducted a separate loading test, giving approximately 63 mg of oxalate from the respective spice. [11]

Despite virtually identical total oxalate loads, oxalate excretion in urine was significantly higher after turmeric than after cinnamon or the control treatment. The researchers considered the most likely explanation to be the difference in solubility: approximately 91% of oxalates in turmeric were soluble, while only 6% of oxalates in cinnamon were soluble. [12]

The study shows that turmeric oxalates are actually absorbed and increase urinary oxalate, rather than simply being present in the plant's laboratory analysis. However, it doesn't answer another question: how often does 2-3 grams of turmeric daily actually lead to stone formation? There were only 11 participants, all healthy, the observation period lasted several weeks, and stone formation was not a study endpoint.

Therefore, the correct conclusion is that regular gram-sized amounts of turmeric may increase one of the risk factors for calcium oxalate stone formation, especially in predisposed individuals. The data do not support the assertion that such a dose necessarily "causes stones."

How much oxalate can be found in modern supplements?

New evidence suggests that the problem cannot be assessed solely by studies of regular turmeric powder.

In a 2026 study, researchers directly measured the oxalate content of popular commercial herbal supplements. Turmeric products were among the options with the highest oxalate content. In mixed turmeric preparations, oxalate levels ranged from approximately 2.69 to 54.8 mg per gram, while in the single-ingredient turmeric preparations studied, oxalate levels ranged from approximately 15 to 19.5 mg per gram. [13]

When considering the manufacturer's recommended serving size, the range became even more striking. In some turmeric products studied, one daily serving contained approximately 48-93 mg of oxalate, while other products contained significantly less. The researchers specifically cautioned that the composition may vary between products and even batches, so these values cannot be generalized to the entire market. [14]

This is more important than it seems. The label may list "turmeric extract," "curcumin," "95% curcuminoids," or a combination with black pepper, but the oxalate content is usually not listed at all.

Therefore, a person with recurrent calcium oxalate stones cannot reliably determine their oxalate load from the front of the package alone.

Turmeric powder and curcumin are not the same thing in terms of oxalate content.

The risk of oxalate loading is primarily related to the plant material and the specific composition of the supplement, rather than the fact that the curcumin molecule is somehow converted to oxalate.

A 2008 study examined turmeric powder. A 2026 study found that even modern commercial supplements labeled as turmeric and curcumin can contain significantly different amounts of oxalate. This means that the word "extract" alone does not guarantee low oxalate content. [15]

On the other hand, it's impossible to assume that any highly purified curcumin preparation necessarily contains the same amount of oxalate as the original rhizome powder. The content depends on the production technology, and therefore, the analysis results of one supplement cannot be generalized to another.

In practice, this makes an important difference: if a person takes turmeric in the form of grams of ground rhizome, the oxalate load is quite predictable as a potential problem. If a concentrated extract is used, it cannot be reliably assessed without analyzing the specific product.

Who needs special care with turmeric?

This issue is of greatest importance not for all people, but for certain risk groups.

Situation	Why turmeric may matter more	What is reasonable to do?
Recurrent calcium oxalate stones	Additional dietary oxalate may increase urinary oxalate	Do not use large daily doses without evaluating diet and daily urine output.
Elevated oxalate in daily urine	The direct factor of stone formation is already present	Limit concentrated sources of oxalate individually
Bariatric surgery or severe malabsorption	Intestinal absorption of oxalate is enhanced	A separate dietary strategy is required
Chronic diarrhea and some intestinal diseases	Hyperoxaluria and decreased protective urinary citrate may occur.	Discuss supplements with your doctor or dietitian.
Preexisting oxalate nephropathy	A high oxalate load is particularly undesirable.	Do not start turmeric in high doses on your own.
Stone of unknown composition	It is unclear whether oxalate plays a significant role.	If possible, examine the stone composition and risk factors
No stones or hyperoxaluria	The risk from normal dietary amounts is much less clear	There is no reason to exclude turmeric from your regular diet.

The 2025 CARI and National Kidney Foundation guidelines emphasize an individualized approach: the preventive diet depends on the composition of the stones and the results of urine tests, not on a single food item. [16]

If the stones were already there

The first question is what the stone was made of. Turmeric oxalate is primarily useful for calcium oxalate stones and especially for elevated urinary oxalate levels. For uric acid, struvite, or cystine stones, the mechanisms are completely different. [17]

If a stone is recovered after spontaneous passage or surgery, laboratory analysis helps determine further prevention. Current CARI guidelines strongly recommend compositional analysis for recurrent stones. For patients with recurrences, multiple stones, or high risk, 24-hour urine testing is also recommended, including oxalate, calcium, citrate, sodium, and volume. [18]

So, a history of kidney stones doesn't necessarily mean a person needs to avoid all oxalate-containing foods. Understanding your metabolic profile is far more helpful.

How to tell if oxalate is really elevated

The most informative method is collecting urine over 24 hours. The European Association of Urology indicates that oxalate excretion greater than 0.40 mmol per day in an adult corresponds to hyperoxaluria; values greater than 0.5 mmol per day particularly suggest secondary intestinal hyperoxaluria, although interpretation always depends on the clinical context. [19]

Reference ranges vary slightly between laboratories. For example, the Mayo Clinic cites a range of approximately 9.7–40.5 mg oxalate per 24 hours for adults. Therefore, it's best to interpret the specific result based on the standards of the laboratory where the test was performed, along with other urine parameters. [20]

A single elevated value also doesn't always explain the cause. Oxalate is influenced by diet, intestinal absorption, vitamin C, the amount of calcium in the diet, and a number of medical conditions. Therefore, for repeat stone formers, modern assessment considers oxalate in combination with calcium, citrate, sodium, volume, and other indicators. [21]

Why can't you just remove calcium from your diet?

This is one of the most common mistakes with calcium oxalate stones.

It seems logical: if a stone contains calcium, then you should eat less calcium. But in the intestines, dietary calcium binds oxalate, forming a poorly absorbed complex that leaves the body in the stool. If there is insufficient calcium in the intestines, more free oxalate can be absorbed and then excreted in the urine. [22]

Current CARI guidelines therefore advise people with calcium stones to maintain adequate dietary calcium intake, especially if urinary oxalate levels are elevated. The National Kidney Foundation offers similar practical advice: combine calcium-rich foods with oxalate-containing foods in the same meal. [23]

This also applies to turmeric as part of food. If a person uses it in a dish and doesn't need to limit dairy products or other sources of calcium for medical reasons, a normal amount of dietary calcium is a more reasonable strategy than taking turmeric while following a low-calcium diet.

This doesn't mean everyone needs to buy calcium tablets on their own. Calcium supplements have their own characteristics and should be selected individually; preference is usually given to normal calcium intake from food. [24]

Is a strict low-oxalate diet necessary?

For most people with calcium oxalate stones, no.

The new 2025 CARI guidelines explicitly discourage the use of a general low-oxalate diet for calcium oxalate stones. The authors point out that there is little evidence that strict oxalate restriction reduces recurrence, while such a diet can worsen nutritional quality by excluding many beneficial plant foods. [25]

The National Kidney Foundation, in its 2026 update, formulates its approach slightly differently: limiting foods with very high oxalate content should be done primarily when truly necessary, such as in the case of calcium oxalate stones and elevated urinary oxalate. The Foundation specifically lists turmeric supplements among foods that may have a high oxalate load in such patients. [26]

These positions are essentially non-conflicting. Both move away from a blanket ban on dozens of vegetables, nuts, and fruits, and suggest focusing on specific sources with high nutrient loads and individual test results.

Therefore, a person with hyperoxaluria may have a perfectly reasonable basis for eliminating daily gram doses of turmeric without committing to a lifelong, extremely strict "oxalate-free" diet.

Why gut diseases increase the importance of oxalates

Normally, some dietary oxalate is bound to calcium in the intestine and excreted in the stool. When fat absorption is impaired, the situation changes: free fatty acids bind calcium, leaving less available for oxalate. As a result, more soluble oxalate remains free and is absorbed in the colon. [27]

This mechanism—intestinal hyperoxaluria—is possible after certain bariatric surgeries, short bowel syndrome, exocrine pancreatic insufficiency, inflammatory bowel disease, and other conditions with malabsorption. European guidelines identify secondary hyperoxaluria as a separate clinical category. [28]

For these people, an additional 40-60 mg of highly soluble oxalate may have a different meaning than for a healthy person with normal intestinal absorption.

Therefore, the popular advice “turmeric is natural and can be taken daily” is especially ill-suited for patients after gastrointestinal surgery or with chronic malabsorption.

Has oxalate nephropathy been reported with turmeric?

Yes, but we are still talking about individual clinical cases, and not about a common complication.

In 2024, nephrologists described a 69-year-old man whose kidney function had deteriorated sharply over several months. A biopsy revealed massive deposition of calcium oxalate crystals in the renal tubules—oxalate nephropathy. The patient reported taking 2 g of turmeric daily for approximately two years, which the authors estimated to be approximately 40 mg of oxalate per day. His daily oxalate excretion was 68 mg, compared to the laboratory's reference range of 7–24 mg. [29]

The patient's condition was severe and hemodialysis was required. After discontinuing the supplement, changing her diet, and other therapy, her kidney function partially improved to the point that dialysis could be discontinued, but chronic decline in kidney function persisted. [30]

However, attributing everything to turmeric alone would be incorrect. The patient had chronic diarrhea following prolonged antibiotic therapy, markedly low urinary citrate, and other conditions that could increase oxalate load and stone formation. The authors themselves consider the development of nephropathy to be a combination of factors. [31]

Therefore, this case does not allow us to calculate the risk of oxalate nephropathy from turmeric and does not prove that 2 grams daily is dangerous for most people. Its significance lies elsewhere: in the presence of additional factors, even an over-the-counter herbal supplement can become a clinically significant source of oxalate.

In animal studies, curcumin, on the contrary, "protects against stones": how is this possible?

This apparent contradiction often leads to incorrect conclusions.

In experiments on mice and rats, purified curcumin did reduce calcium oxalate crystal deposition and signs of oxidative and inflammatory damage to kidney tissue. For example, in a 2019 mouse model, curcumin reduced crystal formation after artificially induced hyperoxaluria. [32]

However, this was an animal experiment using a purified compound, not a clinical trial of people taking turmeric powder. It doesn't show that curcumin prevents recurrence of stones in humans.

At the same time, human research on turmeric powder shows a completely different factor - the product itself brings in well-absorbed oxalate and increases urinary oxalate. [33]

Both results may be true simultaneously. The curcumin molecule in the experimental model is capable of influencing inflammatory processes, while the plant material from which it is derived simultaneously contains oxalates.

The National Kidney Foundation therefore does not recommend herbal supplements as a proven method for kidney stone prevention and specifically notes the potentially high oxalate content of turmeric supplements.[34]

Regular turmeric in food: should you be afraid of it?

For most people, no.

The National Kidney Foundation classifies spices, including turmeric, as foods considered acceptable in normal culinary use, while advising caution with large amounts and food additives.[35]

The difference depends on the dose. A pinch of turmeric in a dish and 2-3 grams of powder daily for months have different effects. A commercial supplement can provide an even higher oxalate load, and its exact content is often unknown. [36]

For a healthy person without stones, without hyperoxaluria and without intestinal diseases, there is no reason to exclude turmeric only because of the presence of oxalates.

Particular caution begins where the spice becomes a regular supplement in gram quantities or where the person already has a proven tendency to calcium oxalate stones.

What to do if you take turmeric and have had stones before

First, it makes sense to determine the composition of the previous stone, if known. For the calcium oxalate type, it's especially helpful to monitor the oxalate level in your 24-hour urine. For people with recurrent stones, current recommendations recommend metabolic testing specifically for individualized prevention. [37]

If urinary oxalate is elevated, daily turmeric powder or a supplement with unknown oxalate content is an obvious source to consider. The National Kidney Foundation specifically lists turmeric supplements as foods that can contribute significant oxalate load. [38]

At the same time, you shouldn't sharply reduce calcium in your diet. A normal intake of dietary calcium during meals helps bind oxalate in the intestines. [39]

Another basic measure is adequate fluid intake. CARI recommends that people with kidney stones maintain a daily urine output of at least 2.5 liters, unless there are medical reasons to restrict fluid intake. [40]

Finally, it makes sense to evaluate the diet as a whole. High sodium intake can increase urinary calcium, and insufficient fluid intake increases the concentration of all stone-forming substances. For many patients, these factors are more important than a single spice. [41]

What not to do

Don't try to "neutralize" a high daily dose of turmeric with massive amounts of calcium supplements. Calcium binding to oxalate is a real mechanism, but calcium supplements require individualized consideration. Normal dietary calcium is generally preferred. [42]

There's no need to automatically exclude all plants, vegetables, nuts, and fruits. The new CARI guidelines explicitly warn that an overly strict low-oxalate diet can impair nutritional quality and lacks compelling evidence for most patients. [43]

Don't assume an "oxalate rating" from a random online table is completely accurate. Oxalate content varies between varieties, products, and preparation methods, and a 2026 study of additives shows enormous variability even within a single category. [44]

Finally, curcumin should not be used as a preventative measure for stones based on mouse studies. There is no human evidence for such use. [45]

When medical help is needed

Turmeric alone doesn't cause any specific set of stone symptoms. If the stone begins to move into the ureter, sharp pain in the side, back, lower abdomen, or groin, blood in the urine, frequent or painful urination, nausea, and vomiting are possible. [46]

You should especially seek medical attention promptly if you experience severe pain along with fever or chills, or if urine has stopped flowing or is only passing in small amounts. A stone blocking the ureter due to infection requires urgent evaluation. [47]

In contrast, decreased kidney function in oxalate nephropathy can develop much more subtly. The patient described here, with severe kidney damage, had virtually no characteristic urinary symptoms, and the problem was discovered through a blood test. Therefore, for someone with chronic kidney disease, malabsorption, or severe hyperoxaluria, it's wiser to discuss long-term, high-dose herbal supplements in advance rather than relying solely on how they feel. [48]

What is often misunderstood

"If turmeric contains oxalates, it causes stones in everyone." No. A human study showed an increase in urinary oxalate, but not in the incidence of stones. The risk depends on predisposition and other urine parameters. [49]

"With calcium oxalate stones, calcium must be eliminated." Conversely, a lack of dietary calcium can increase intestinal absorption of oxalate. Current recommendations recommend maintaining normal calcium intake. [50]

"Any curcumin contains as much oxalate as turmeric powder." This is unknown. Analysis of commercial supplements shows a wide range of oxalate content; it depends on the specific product. [51]

"Curcumin prevents stones because studies have shown it does." Positive data of this kind have been obtained primarily in experimental animal models. There is no reliable evidence for preventing stone recurrence in humans. [52]

"Oxalates should be completely eliminated from the diet." Current CARI guidelines, on the other hand, do not recommend a universal low-oxalate diet. A more rational approach is an individualized one, with adequate dietary calcium and limiting excessively concentrated sources in cases of hyperoxaluria. [53]

"If the supplement is natural, the amount doesn't matter." In a human study, just a few grams of turmeric daily increased oxalate excretion, and some modern commercial supplements contain tens of milligrams of oxalate.[54]

Key points from experts

Christina Penniston, PhD, RD, is a senior research fellow in the Department of Urology at the University of Wisconsin School of Medicine and Public Health and provides nutritional care to patients with urologic conditions at UW Health. Her professional work focuses on nutrition and kidney stones. [55]

A research team including Penniston directly measured oxalate in popular over-the-counter herbal supplements in 2026. Turmeric-based supplements were among the products with the highest, yet highly variable, oxalate loads. This finding supports a practical approach in which patients with calcium oxalate stones are assessed not by the abstract herbal name, but by the specific supplement, dosage, and metabolic parameters. [56]

Kimora Scotland, MD, PhD, is a urologist and associate professor of urology at the University of California, Los Angeles, and director of endourology research; her clinical specialty includes the treatment of kidney stones. [57]

Scotland was also part of the original study team for a study of commercial herbal supplements. The study team concluded that due to the high popularity of such products and the significant variability in oxalate content, clinicians working with stone patients should consider supplements as a potential source of oxalate burden.[58]

Frequently Asked Questions

Are there many oxalates in turmeric?

Yes, the powder tested contained a lot of it—about 19.7 mg of total oxalate per gram, with approximately 91% in soluble form. The composition of other batches and products may vary. [59]

How much turmeric was used in the study that increased urine oxalate?

About 2.8 g per day for four weeks, which provided approximately 55 mg of oxalate daily. The study included only 11 healthy volunteers. [60]

Does this mean that 2.8g of turmeric causes stones?

No. The study showed an increase in urinary oxalate, but not stone formation. The absolute risk of stone formation from this dose in a healthy person is unknown.

Can I take turmeric if I previously had calcium oxalate stones?

A small amount of the spice isn't necessarily prohibited, but daily gram doses and concentrated supplements should be reconsidered, especially if oxalate levels in the urine are elevated. The National Kidney Foundation specifically recommends considering turmeric supplements in such patients. [61]

What if the stone was of a different type?

Turmeric oxalate is most directly associated with calcium oxalate stones. Prevention recommendations for other types vary, so it's helpful to know the stone's composition. [62]

Can you take pure curcumin instead of turmeric powder?

A product name alone does not guarantee oxalate-free status. A recent analysis of commercial supplements has revealed wide variations even among products marketed as turmeric or curcumin. If the issue is significant due to recurrent stones, information on the specific composition of the product is required. [63]

Will taking turmeric with milk or yogurt help?

Dietary calcium can bind oxalate in the intestines and reduce its absorption. Therefore, current recommendations recommend getting adequate dietary calcium and combining it with oxalate-containing foods. However, this does not guarantee that a large dose of turmeric is safe. [64]

Should I go on a strict low-oxalate diet after a stone?

Generally, no. CARI's 2025 guidelines specifically advise against a universal low-oxalate diet and suggest individually adjusting the most significant sources based on urine analysis and overall diet. [65]

Which people are particularly sensitive to dietary oxalate?

The risk is higher in cases of intestinal hyperoxaluria—for example, after certain bariatric surgeries, with impaired fat absorption, chronic diarrhea, and a number of intestinal diseases. Under such conditions, the absorption of dietary oxalate can increase significantly. [66]

Can turmeric cause severe kidney damage?

At least one well-documented case of oxalate nephropathy has been reported in patients taking 2 g of turmeric daily for many years, but the patient had other significant risk factors. It is impossible to estimate the incidence of this complication from a single case.[67]

How much water should you drink to prevent stones?

For people with kidney stones, CARI recommends drinking enough fluid to produce at least 2.5 liters of urine per day, unless there is a medical fluid restriction. Actual fluid intake depends on climate, physical activity, and fluid loss. [68]

Result

Turmeric is a significant source of well-absorbed oxalate. In a small human study, 2.8 g of turmeric per day provided approximately 55 mg of oxalate and increased its urinary excretion. This supports a valid mechanism by which regular high doses of turmeric may increase the risk in individuals predisposed to calcium oxalate stones. [69]

However, this does not mean that regular turmeric in food is dangerous for everyone. Current recommendations do not support a universal ban on oxalates, much less a low-calcium diet. For people with recurrent calcium oxalate stones, it is much more important to measure oxalate and other daily urine parameters, maintain adequate dietary calcium intake, limit sodium, and ensure adequate urine volume. [70]

Daily supplements and gram doses of turmeric powder should be approached with particular caution. New analytical data from 2026 shows that different commercial products can contain radically different oxalate loads, which cannot be determined solely from the label. [71]

Particular caution is warranted in patients with pre-existing elevated urinary oxalate levels, recurrent calcium oxalate stones, intestinal malabsorption, bariatric surgery, and pre-existing oxalate nephropathy. In these situations, the decision to use concentrated turmeric is best made after assessing the specific metabolic risk, rather than based on the product's "natural" status.