People taking popular medications like Ozempic, Wegovy, and Rybelsus for weight loss are at higher risk for potentially serious stomach and intestinal issues, compared to people taking a weight loss drug approved in 2014, a large study reveals.

Those taking one of these drugs, known as glucagon-like peptide-1 (GLP-1) receptor agonists, were nine times more likely to have pancreatitis, an often painful inflammation of the pancreas, compared to others taking a combination of naltrexone and bupropion for weight loss (brand name Contrave).

Other findings show that people taking these drugs: Were over four times more likely to get a bowel obstruction, which prevents food from going through the large or small intestines, with symptoms like nausea, vomiting, cramping and/or bloating; Were more than three-and-a-half times more likely to get stomach paresis, a blockage of food in the stomach that can cause nausea, vomiting, and stomach pain.

The study was published today in the Journal of the American Medical Association. Researchers say their findings are not about scaring people off the weight loss drugs, but instead about increasing awareness that these potential adverse outcomes can happen. That way, people can consider the risks and benefits before starting these medications. People taking these drugs for weight loss have about a 1% to 2% chance of having these events, including a 1% risk for stomach paresis, said Mahyar Etminan, PharmD, the study’s senior author and an expert in drug safety and pharmacoepidemiology at the University of British Columbia in Vancouver, Canada.

Given the popularity and wide use of these drugs, these adverse events, although rare, “must be considered by patients thinking about using them for weight loss,” co-author Mohit Sodhi, a graduate of the University of British Columbia’s Experimental Medicine Program and fourth year medical student, said in a news release about the study. People taking a GLP-1 to treat diabetes might be more willing to accept the risks, Etminan said, given their potential advantages, especially for lowering the risk of heart problems. “But those who are otherwise healthy and just taking them for weight loss might want to be more careful in weighing the risk/benefit equation,” he said.