University of Pennsylvania researchers analyzed more than 400,000 Reddit posts to examine the experiences of people using GLP-1 drugs. Published in Nature Health, the study covered posts made over more than five years by approximately 70,000 Reddit users taking semaglutide (Ozempic, Wegovy and Rybelsus) or tirzepatide (Mounjaro and Zepbound).
The study found that 44% of the users included in the analysis reported at least one side effect. The most common complaints were nausea and other digestive system problems previously associated with these drugs. However, two distinct categories emerged that the researchers considered worthy of further investigation: reproductive symptoms, such as changes in the menstrual cycle, and body temperature issues, such as shivering, feeling unusually cold and hot flashes. Approximately 4% of users who reported side effects mentioned reproductive symptoms. Fatigue was also the second most frequently reported complaint in the Reddit data, while in only a small number of clinical trials was this symptom reported frequently enough to reach established reporting thresholds.
The researchers emphasized that the findings do not prove that GLP-1 drugs cause these symptoms. Neil Sehgal said that approximately 4% of users reported menstrual irregularities and that this could be a signal worth investigating, noting that the rate could be higher in a sample consisting only of women. One possible reason the symptoms warrant attention could be that the hypothalamus, which regulates appetite, hormones, reproduction and body temperature, plays a role in the mechanism of action of these drugs; however, this connection is also not considered evidence of causality.
The study used large language models to convert patients’ statements written in everyday language into standard medical categories. The researchers stated that models such as GPT and Gemini made it possible to classify very large text datasets more quickly and consistently. It was noted that Reddit users do not represent GLP-1 users overall; they are a group that is younger, has a higher proportion of men and is predominantly based in the US.
The team said that social media data cannot replace clinical studies, but could reveal potential health signals more quickly once the drugs begin to be used by broad segments of the population. The researchers want to examine whether the same patterns are observed on different platforms and in communities outside the English-speaking world. The study was conducted at the University of Pennsylvania School of Engineering and Applied Science; the authors reported no external funding.
Why it matters
This study raises the question of whether symptoms that do not reach established reporting thresholds in clinical research could be detected earlier in users’ everyday accounts. In this respect, social media data could provide an additional resource for drug safety monitoring; however, the fact that Reddit users do not represent GLP-1 users overall limits the direct generalization of the findings to the broader population. Although AI-assisted classification makes it easier to organize patterns in large text datasets, this method does not turn observations in the posts into medical diagnoses or cause-and-effect relationships. Therefore, the key unresolved issue is whether reports related to reproduction and body temperature will be confirmed across different platforms and against clinical data.
Background
Reddit is not a new name in the FikirPilot archive: in the last 90 days, we published a news article in which this name appeared; that article was dated 1 September 2026.