New ICD Code Clarifies Cannabis Hyperemesis Syndrome as ER Visits Rise

A patient arrives at the emergency room gripped by severe, unrelenting nausea and vomiting. The symptoms began within hours of their last cannabis use and show no sign of stopping. They've been here before—multiple times, in fact—but each visit has ended with a different diagnosis, a different treatment, and thousands of dollars in medical bills. What they're experiencing is cannabis hyperemesis syndrome, a gastrointestinal condition that has only recently acquired an official name and a place in medical record-keeping.

Until October of this year, doctors had no standardized way to document this condition. They worked around it, using multiple imprecise codes, watching the same patients cycle back through their doors without recognizing the pattern. On October 1st, the World Health Organization added cannabis hyperemesis syndrome to the International Classification of Diseases, assigning it the code R11.16. The Centers for Disease Control and Prevention incorporated the same code into U.S. diagnostic systems. It was a quiet administrative change with significant consequences.

The syndrome itself is straightforward in its presentation: severe vomiting that emerges within a day of cannabis use and can persist for several days. People who develop it typically experience these episodes three or four times per year. What makes it clinically important is that it now has a single, specific billing code. Clinicians can document it precisely. Providers can recognize repeat episodes when patients return. Most critically, researchers can finally count these cases with accuracy.

Beatriz Carlini, a research associate professor at the University of Washington School of Medicine who studies the adverse health effects of cannabis, sees the new code as a tool for understanding a public health problem that has been largely invisible. "In studying addiction and other public health concerns, we have three sources of data: what clinicians tell us, what people in the communities tell us, and what health records tell us," she explained. "A new code for cannabis hyperemesis syndrome will supply important hard evidence on cannabis-adverse events, which physicians tell us is a growing problem." The code transforms anecdotal reports into trackable data.

Yet diagnosis remains difficult, in part because awareness is still limited. Many emergency medicine providers have only recently learned the condition exists. Patients often require multiple visits before anyone recognizes what is happening to them. Dr. Chris Buresh, an emergency medicine specialist with UW Medicine and Seattle Children's, noted that a person can accumulate thousands of dollars in medical costs across several emergency department visits before the correct diagnosis arrives. The delay compounds both the financial and physical burden.

Patient resistance adds another layer of complexity. Cannabis is widely known and used to relieve nausea in people undergoing chemotherapy or living with conditions like HIV and migraines. When a doctor tells someone that cannabis is causing their severe vomiting, the diagnosis can seem implausible or even contradictory. Some patients report using cannabis without problems for decades. Others deliberately use it believing it will treat their nausea. "It seems like there's a threshold when people can become vulnerable to this condition, and that threshold is different for everyone," Buresh said. "Even using in small amounts can make these people start throwing up."

The underlying mechanism remains a mystery. Researchers do not yet know why the syndrome affects some cannabis users but not others. Whether it correlates with the increasing availability of cannabis, the rising potency of THC in modern products, or some other factor entirely remains unclear. Treatment is equally challenging. Standard anti-nausea medications often fail to work reliably. Clinicians sometimes resort to second and third-line options like Haldol, a medication typically used for psychotic episodes. Some patients report finding limited relief through capsaicin cream, an over-the-counter warming agent applied to the abdomen, or through prolonged hot showers—a remedy so common that Buresh uses it as a diagnostic clue. "That's something that can clinch the diagnosis for me, when someone says they're better with a hot shower. Patients describe going through all the hot water in their house," he said.

Recovery itself can be elusive. Because the syndrome appears intermittently, users may assume an episode was unrelated to their cannabis use and continue without immediate consequences, only to become severely ill again. For those who accept the diagnosis and attempt to stop using cannabis, addiction can make abstinence difficult. The new ICD code provides clarity and documentation, but it does not yet provide answers about why this happens or how to reliably make it stop.