Can THC Cause Kidney Stones? What the Evidence Says

No published study has shown that THC directly causes kidney stones. In fact, the largest epidemiological analysis on the topic, a cross-sectional study of U.S. national health survey data spanning nearly a decade, found that marijuana use was associated with a lower likelihood of kidney stones in men. That finding is surprising enough to warrant a closer look, because the relationship between cannabis and your kidneys is more layered than a simple yes-or-no answer suggests.

What the Largest Population Study Actually Found

The most direct evidence comes from a 2023 study that analyzed data from the National Health and Nutrition Examination Survey (NHANES) collected between 2009 and 2018. Researchers looked at the relationship between marijuana use and self-reported kidney stone history in a nationally representative sample. After adjusting for factors like age, diet, and medical conditions, marijuana use in men was associated with roughly 28% lower odds of having kidney stones. Men who used marijuana one to seven times per week had even lower odds, about 38% lower than non-users.¹

Before you conclude that cannabis protects your kidneys, keep some important caveats in mind. This was a cross-sectional study, meaning it captured a snapshot in time rather than following people over years to see who developed stones. It cannot prove that cannabis prevented anything. People who use marijuana and people who don’t differ in many ways that the study may not have fully accounted for. And the protective association appeared only in men; the results in women were less clear. Still, the study is significant because it is the best large-scale epidemiological data available, and it points away from cannabis being a stone-causing substance.

Why THC Wouldn’t Directly Form Stones

Kidney stones form when certain minerals and salts in your urine become concentrated enough to crystallize. The most common type, calcium oxalate stones, develops when calcium and oxalate levels in urine are high, urine volume is low, or urine lacks substances that prevent crystals from sticking together. For a drug to directly cause stones, it would need to change the chemistry of your urine in ways that favor crystallization, either by increasing stone-forming minerals, reducing protective factors, or shrinking urine volume.

THC does not do any of these things through its known pharmacological actions. It is processed by the liver and excreted largely through the bile and feces, with relatively little leaving the body through urine. Unlike some medications that are well-documented stone culprits (certain antibiotics, some HIV medications, high-dose vitamin C supplements), THC and its metabolites do not precipitate in the urinary tract or alter calcium or oxalate excretion in any way researchers have identified.

The Endocannabinoid System Lives in Your Kidneys

Your kidneys do have cannabinoid receptors, which is one reason researchers are interested in this topic at all. Studies have confirmed that the CB1 cannabinoid receptor is present in several key parts of the kidney, including the tubule cells responsible for filtering and concentrating urine. The CB2 receptor, by contrast, appears to be absent from normal kidney tissue.² The endocannabinoid system as a whole plays a role in kidney physiology and has emerged as a factor in conditions like diabetic kidney disease and drug-related kidney toxicity.³

Interestingly, a 2025 bioinformatics study looking for genes associated with kidney stone formation identified CNR1, the gene that encodes the CB1 cannabinoid receptor, as one of seven key biomarkers in an early-diagnosis model for renal stones.⁴ That does not mean activating CB1 causes stones. It means the cannabinoid receptor system is biologically connected to the pathways involved in stone formation in ways scientists are still working out. Research on cannabinoid receptors in the kidney has shown that activating them can produce both harmful and helpful effects depending on the context, the type of kidney injury, and the timing of the exposure.⁵

This is worth noting because it underscores that “cannabis doesn’t cause kidney stones” is not the same as “cannabis has no effect on your kidneys.” The endocannabinoid system is deeply woven into kidney function, and the full picture of how THC interacts with it over years of regular use is still being studied.

The Real Kidney Risk from Heavy Cannabis Use

While kidney stones don’t appear to be a direct consequence of THC use, there is a genuine kidney risk that heavy cannabis users should know about, and it comes through an indirect route. Cannabinoid hyperemesis syndrome (CHS) is a condition that can develop in people who use cannabis frequently over months or years. The hallmark of CHS is cycles of severe, uncontrollable nausea and vomiting that can last one to two days at a time. During those episodes, the fluid loss from vomiting can become severe enough to cause dehydration, electrolyte imbalances, and acute kidney injury.⁶

Acute kidney injury from CHS-related dehydration is not the same thing as kidney stones, but it matters for two reasons. First, CHS is probably underdiagnosed because many patients and even some doctors don’t connect repeated vomiting episodes with cannabis use. Second, dehydration itself is a genuine risk factor for kidney stones. When you’re dehydrated, your urine becomes more concentrated, giving stone-forming minerals a better chance to crystallize. Someone who experiences repeated CHS episodes could, in theory, create conditions that favor stone development, even though the stones themselves aren’t caused by THC.

The fix for CHS is straightforward in principle, though difficult for many patients in practice: stop using cannabis. Symptoms resolve once cannabis use ceases, and the kidney injury from dehydration typically reverses with fluid replacement. But people who experience CHS and continue using cannabis set themselves up for repeated bouts of dehydration, which isn’t great for long-term kidney health by any measure.

The “Munchies” Factor and Stone-Friendly Diets

There’s another indirect pathway worth discussing, and it involves what you eat and drink while using cannabis. THC is associated with increased appetite, food cravings, a tendency to overconsume, and decreased physical activity.⁷ Anyone who has experienced the munchies knows the cravings tend to lean toward salty, sugary, and processed foods rather than leafy greens.

This matters because diet is one of the biggest modifiable risk factors for kidney stones. High sodium intake increases calcium excretion in urine. Diets heavy in animal protein can raise uric acid levels. Sugary drinks, particularly those high in fructose, have been linked to higher stone risk. If regular cannabis use consistently pushes you toward these kinds of dietary choices, it could indirectly contribute to stone-forming conditions in your urine over time, even though the THC molecule itself isn’t the culprit.

That said, the population study discussed earlier still found lower stone rates among male marijuana users. Whatever dietary effects the munchies might have, they didn’t overwhelm the overall association in that dataset. It’s possible that other aspects of cannabis users’ lives, perhaps higher fluid intake (cannabis often makes people thirsty) or younger average age, offset the dietary risk. Researchers don’t have a clear answer on this yet.

Synthetic Cannabinoids Are a Completely Different Problem

One area where the kidney risk from cannabinoids is well documented involves synthetic cannabinoids, the compounds sold under street names like K2 or Spice. These are not THC. They are lab-made chemicals designed to bind to cannabinoid receptors, and they often do so far more powerfully and unpredictably than natural THC. Acute kidney injury related to synthetic marijuana has become an increasingly common phenomenon, particularly among young men, who make up the demographic that uses these products most frequently. The exact mechanism isn’t fully established, but direct damage to kidney tissue appears to be the most likely explanation.⁸

The good news is that K2-related kidney injury usually resolves quickly with intravenous fluids, and most patients don’t suffer permanent kidney damage. The bad news is that these products are unregulated, the chemical composition varies wildly from batch to batch, and users often don’t know what they’re actually consuming. A narrative review of kidney effects from recreational drugs noted that the endocannabinoid system is present at low levels in kidney cells, including podocytes and mesangial cells, which are the structural components of the kidney’s filtering units.⁹ Synthetic cannabinoids, which hit these receptors much harder than THC does, appear capable of overwhelming the system in ways that natural cannabis doesn’t.

If you’re asking whether “cannabis” can hurt your kidneys and you’re thinking about synthetic products, the answer is much less reassuring than if you’re asking about marijuana flower or standard THC edibles. The distinction matters enormously and gets lost in casual conversation.

What About Using Cannabis When You Already Have Stones

A related question many people have is whether cannabis is safe or even helpful when you’re dealing with an existing stone. Kidney stone pain is famously excruciating, and some patients turn to cannabis for relief. A randomized, placebo-controlled trial tested cannabidiol (CBD) oil for pain after ureteroscopy, a common procedure for removing kidney stones. That study did not find CBD oil to be effective for post-procedure pain management.¹⁰

CBD is not THC, of course, and the two have very different pharmacological profiles. Some people report that THC-containing products help them manage stone-related pain, but no controlled trial has tested that specific claim. If you’re in the middle of passing a stone, the bigger concern with cannabis is probably practical: if heavy use has contributed to dehydration or poor fluid intake, that could slow things down. Adequate hydration is the single most important thing you can do to help pass a stone, so anything that works against that goal is counterproductive.

Who Should Still Be Cautious

Even though the evidence doesn’t support a direct link between THC and kidney stones, some groups of people should pay closer attention to how cannabis might affect their kidney health indirectly:

• Heavy daily users: The risk of developing cannabinoid hyperemesis syndrome increases with frequency and duration of use. If you’ve experienced unexplained cyclical vomiting, consider CHS as a possibility and be aware that the dehydration it causes is harmful to your kidneys.
• People with chronic kidney disease: The endocannabinoid system is involved in the progression of chronic kidney disease and diabetic nephropathy. While research hasn’t established that cannabis worsens these conditions, the science is unsettled enough that caution makes sense.
• People prone to recurrent stones: If you’ve had multiple kidney stones, you’re already at higher risk for more. Anything that contributes to dehydration, poor diet, or inconsistent fluid intake matters more for you than for the general population. Be mindful of how cannabis use affects your eating and drinking habits.
• Users of synthetic cannabinoids: The risk of acute kidney injury is real and documented. If you’re using products that aren’t regulated cannabis from a licensed source, you’re taking on a kidney risk that doesn’t apply to standard THC.

The State of the Science

Research on cannabis and kidney stones is thin. The NHANES analysis is the only large epidemiological study specifically designed to look at this question, and it has the inherent limitations of cross-sectional survey data. No long-term prospective study has followed cannabis users and non-users over time to see who develops stones. No laboratory study has examined whether THC or its metabolites alter the urinary environment in ways that promote or inhibit crystal formation.

The identification of the CNR1 gene as a biomarker associated with stone formation opens an intriguing line of research, but it’s a computational finding that needs biological validation. It tells us the cannabinoid receptor system is somehow involved in the molecular landscape of kidney stones, not that activating or blocking that receptor changes your risk in a particular direction.

What researchers can say with more confidence is that the endocannabinoid system is present and active in the kidney, that it participates in both normal function and disease processes, and that its effects are context-dependent rather than uniformly good or bad. That’s a frustratingly incomplete answer for someone who just wants to know if their cannabis use is putting them at risk for stones. The honest response is that no evidence suggests it does, one decent study suggests it might not, and the biggest kidney-related risks from cannabis come through side doors like dehydration from CHS and dietary choices driven by the munchies rather than from the molecule itself.