Weight isn’t the only thing people can lose while taking a GLP-1 medication like semaglutide (Wegovy and Ozempic) or tirzepatide (Zepbound and Mounjaro). Some might also experience a profound loss of joy, doctors are warning. In a report out this week, doctors have detailed three cases of their patients developing anhedonia—an inability to feel pleasure—after they started taking tirzepatide for their obesity. Fortunately, this potential side effect seems to be linked specifically to the largest doses of the drug, and all three people began to regain their zest for life after reducing their dosage. Still, doctors should be on the lookout for this possible complication in GLP-1 users, the authors say. “Clinicians should consider monitoring for changes in motivation and reward perception during treatment, particularly at higher doses,” they wrote in their paper, published Tuesday in Obesity Pillars. The loss of joy GLP-1s help people lose weight through several mechanisms, which include reducing people’s cravings for food. In recent years, researchers have found these drugs can also tamp down people’s unhealthy urges for alcohol and other addictive vices like gambling. As a result, scientists are now trialing these drugs as treatments for substance use disorders.