Researchers at the University of Pennsylvania used artificial intelligence to analyze more than 400,000 Reddit posts about GLP-1 medications such as semaglutide and tirzepatide, identifying frequently discussed symptoms—including menstrual changes and temperature-related complaints—that may be less prominent in clinical trial reporting and drug labeling.
A study from the University of Pennsylvania School of Engineering and Applied Science, published in Nature Health in 2026, used large language models to analyze more than 400,000 Reddit posts written by nearly 70,000 users over a period of more than five years.
The researchers reported that many users described side effects commonly associated with GLP-1 drugs, particularly gastrointestinal problems. About 44% of users in the sample mentioned at least one side effect.
The analysis also flagged symptoms that the researchers said may warrant closer scrutiny, while emphasizing that the study does not establish that the medications caused the complaints described online. Nearly 4% of users who reported side effects also described reproductive symptoms, including irregular menstrual cycles, intermenstrual bleeding and heavy bleeding. Users also discussed temperature-related issues such as chills, feeling cold and hot flashes, and fatigue emerged as a frequently mentioned complaint.
The authors suggested that AI-assisted monitoring of large volumes of social media discussion could complement traditional pharmacovigilance by surfacing patient concerns more quickly, while noting that Reddit users are not representative of the broader population and that online reports can be incomplete or biased.
