When Cannabis Causes Vomiting

Key Takeaways >

• Cannabinoid hyperemesis syndrome (CHS) causes repeated attacks of severe nausea, vomiting, and stomach pain, usually in people who have used cannabis daily or almost daily for years.
• Emergency visits linked to CHS have climbed in the US and Canada. Those counts come from billing codes, and they cannot show that legalization itself is the cause.
• Hot showers often ease symptoms for a while, but they do not end the cycle, and long hot showers may worsen dehydration.
• Hospital medicines can help during an attack, though the research behind them is limited. Stopping cannabis is the only approach consistently linked to lasting relief, and no CBD or other cannabis product has been shown to treat CHS.
• CHS can cause dangerous dehydration and kidney injury. Anyone who cannot keep fluids down should get medical care promptly.

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Cannabis has a reputation for settling the stomach, and THC-based medicines are used to treat nausea from chemotherapy [1]. Cannabinoid hyperemesis syndrome runs the other way. In some people who use cannabis heavily over a long period, it brings attacks of intense nausea, repeated vomiting, and abdominal pain that ease and then return [2, 3].

The pattern often goes unrecognized. People with CHS have usually used cannabis for years before symptoms start, most respondents in the largest patient survey bought it from licensed dispensaries, and some reach for more cannabis to calm the nausea [4, 5]. This article explains what CHS looks like, how common it appears to be, why it might happen, what emergency care can offer, and why stopping cannabis remains the one approach consistently linked to lasting relief.

What CHS Looks Like

CHS follows a cycle. Attacks of nausea, vomiting, and stomach pain come in episodes separated by stretches of feeling normal or nearly normal [3, 6]. In the largest patient survey, most respondents (63%) said their early symptoms clustered in the morning, mainly as nausea and stomach pain [4].

Many people with CHS discover that hot showers or baths bring relief, and some spend long stretches under hot water during an attack. A review of published cases found compulsive hot bathing with relief in 92.3% of reported cases [3]. The habit is a useful clue but an imperfect one, because about half of people with cyclic vomiting syndrome (CVS), a similar condition that also occurs in people who do not use cannabis, report it too [1].

The people affected have usually used cannabis daily or near-daily for more than two years [1]. In the patient survey, 96.5% used cannabis at least daily around the time symptoms began, and nearly two-thirds had used it for more than three years before their first symptoms [4]. Flower and vape cartridges were the most common products, and people who used vape cartridges tended to develop symptoms sooner.

No blood test confirms CHS. Doctors make the diagnosis from the pattern of symptoms and cannabis use after ruling out other causes, and most published cases were never followed long enough to confirm that stopping cannabis ended the attacks [6].

How Common Is CHS, and Is It Increasing?

No one knows exactly how common CHS is, because studies define it differently. In a 2023 national online survey of more than 10,000 people in the US, aged 16 to 65, who had used cannabis in the past year, 6% said they had experienced CHS in the previous 12 months [5]. That figure rests on a single question, so it likely includes some vomiting from other causes, such as taking too much cannabis at once.

Hospital records show a clear upward trend. In the US, emergency visits coded in a way that points to CHS rose fivefold between 2016 and 2022, from 4.4 to 22.3 per 100,000 visits, with a spike during the COVID-19 pandemic [7]. In Ontario, Canada, CHS emergency visits rose 13-fold between 2014 and 2021 [8]. These visits mostly involve people in their 20s and early 30s, and women and men now appear in close to equal numbers [7, 8].

Two cautions apply. These counts come from billing codes, which capture suspected cases and repeat visits, and part of the rise may reflect doctors recognizing CHS more often [7]. Coding matters a great deal: when a diagnosis code specific to CHS took effect in October 2025, CHS visits tracked by the CDC more than tripled within a month, a jump the researchers say might partly reflect better recognition and coding [9]. The timing also does not show that legalization caused the increase. In Ontario, the existing upward trend did not change when cannabis was first legalized under tight limits on stores and products. Visits jumped when the market expanded to more stores and products in 2020, which was also when the pandemic began [8].

Why Would Cannabis Cause Vomiting?

The cause is unknown, and so is the reason only some heavy users develop CHS. THC has a two-sided effect on nausea: at low doses it tends to calm it, while at high doses it can trigger vomiting [10]. One leading theory holds that years of heavy THC exposure change the body's own cannabinoid system, disturbing the way it regulates stress and body temperature [10]. Heavy use may also disturb a heat-sensing receptor called TRPV1 [10], which offers one possible explanation for why hot water helps. Researchers also disagree about whether CHS is a condition of its own or a form of CVS set off by cannabis [6].

Claims that CHS is "genetic" have circulated in cannabis media. They trace back mainly to one small study in which 28 people with CHS and 12 comparison users completed genetic testing [11]. Several authors worked for or advised the company that helped fund the study, a patent application on the genetic test had been filed, and the results have not been independently confirmed. Genetics may turn out to matter, but no validated test can tell anyone whether they are at risk.

What Emergency Care Can Offer

An attack severe enough for the emergency room is usually treated with intravenous fluids, replacement of electrolytes (body salts), and anti-nausea medicine, although common anti-nausea drugs often fall short in CHS [12].

Two small randomized trials offer the best evidence so far. In one, 30 patients received either haloperidol, an older antipsychotic drug, or ondansetron, a standard anti-nausea medicine. Haloperidol eased pain and nausea more, and patients who received it left the emergency department two and a half hours sooner on average [13]. Two patients on the higher haloperidol dose came back with acute dystonia, a sudden, involuntary muscle spasm.

In the other trial, 30 patients had capsaicin cream, made from the compound that gives chili peppers their heat, or a placebo cream applied to the abdomen. At 30 minutes, the trial's main test, capsaicin was not clearly better than placebo. By 60 minutes, nausea was lower with capsaicin, and nearly 3 in 10 capsaicin patients had complete relief compared with none on placebo [14].

Emergency medicine guidelines suggest haloperidol or the related drug droperidol, and offering capsaicin cream, alongside usual care, while rating the evidence for each as very low certainty [15]. A 2017 systematic review also lists avoiding opioid pain medicines among supportive measures that may help, though the evidence is limited [3]. These medicines are given under medical monitoring for good reason: droperidol's label carries a boxed warning about dangerous heart-rhythm problems, and low potassium or magnesium, which repeated vomiting can cause, adds to that risk [12, 16]. These treatments can get someone through an attack. None of them prevents the next one.

Why Stopping Cannabis Is the Key to Lasting Relief

Major reviews of CHS reach the same conclusion: stopping cannabis is the one approach consistently linked to lasting relief [1, 3]. In the first published case series, attacks stopped in the seven people who quit and continued in the three who kept using. Three people who went back to cannabis after a break got sick again, and two of them recovered after quitting a second time [2].

This evidence comes from case reports and small case series, and most people in them were followed only briefly [6]. Recovery also takes patience. Because attacks can be months apart, the definition researchers have proposed allows at least six months without cannabis, or the length of three typical cycles, before judging whether stopping has worked [6].

Some popular advice suggests cutting back, switching strains, or taking short breaks. No study has shown that any of these approaches keeps CHS from coming back, and no one has identified an amount of cannabis that people who have had CHS can safely return to.

Quitting can be hard, especially after years of daily use, and many people doubt that cannabis could be causing symptoms when it once seemed to help [1]. Hytiva's Research article on cannabis use disorder, tolerance, and withdrawal covers what the evidence shows about dependence and withdrawal, and a clinician can help plan the process.

CBD and other dispensary products marketed for nausea are not a workaround. No cannabis or CBD product is FDA-approved to treat CHS, and because the FDA has not approved cannabis itself as a treatment for any condition, these products cannot legally be marketed as treatments [17]. No controlled study has tested CBD for CHS, and CBD products can contain THC. An analysis of CBD extracts sold online found THC in 1 in 5 [18]. For someone with CHS, a CBD product is an untested remedy that may add more THC. For a broader look at how cannabis affects digestion, see Hytiva's overview of cannabis and gut health.

When to Get Medical Help

CHS can be dangerous. Repeated vomiting drains the body of fluid and electrolytes [12], and long hot showers may add to the fluid loss [19]. Kidney injury from dehydration has been documented in several case reports, and in rare cases CHS has been fatal [19, 20].

Anyone who cannot keep fluids down, keeps vomiting, or feels faint, very weak, or confused should get medical care promptly. In the emergency department, clinicians can check for dehydration and electrolyte problems and replace fluids [12]. Because cannabis use is central to the diagnosis, telling them how often and in what form cannabis is used gives them what they need to recognize CHS.

Using more cannabis or turning to CBD during an attack is no substitute for care. An emergency visit is also a chance to get the right diagnosis on record, so future care starts in the right place.

The Bottom Line

CHS is a real and increasingly recognized condition in which long-term, frequent cannabis use leads to repeated attacks of severe vomiting. Emergency visits linked to it have risen, although billing data cannot show how much of that rise reflects more cases and how much reflects better recognition.

The evidence establishes the pattern: attacks in heavy, long-term users. Published cases consistently describe lasting relief after sustained abstinence, although few people in them were followed long enough to confirm it. The evidence does not yet explain why some heavy users develop CHS and others do not, whether genetics plays a role, or which hospital treatment works best. Hot showers and hospital medicines can ease an attack without ending the cycle, CBD products have not been shown to help, and no safe level of cannabis use has been identified for people who have had CHS.

For anyone who recognizes this pattern, the most useful steps are to get medical care when vomiting will not stop, tell clinicians about cannabis use, and make stopping cannabis the main goal, with support where needed.

For the full evidence review, including the diagnostic criteria, emergency department trends, treatment trials, and the research that could improve care, see the Research article on cannabinoid hyperemesis syndrome.

Frequently Asked Questions

I threw up after a strong edible. Is that CHS? A single bout of vomiting after taking too much cannabis is different from CHS, which involves repeated attacks in people who use cannabis frequently over a long period [3]. Vomiting that keeps coming back needs medical attention.

Can I keep using cannabis if I cut back or switch products? No study has identified a safe amount or type of cannabis for people who have had CHS. In the first published case series, all three people who resumed cannabis after a break got sick again [2], and stopping completely is the only approach consistently linked to lasting relief [3].

Will CBD help? There is no evidence that it does. No controlled study has tested CBD for CHS, no product is FDA-approved for it, and CBD products sometimes contain THC [17, 18].

How long after quitting do symptoms stop? Researchers' proposed definition allows at least six months, or three typical cycles, before judging whether stopping has worked [6]. Because attacks can be months apart, a break of a few weeks cannot show whether the cycle has ended.

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