A study has revealed GLP-1 medication side effects from real-world data that are not fully captured in clinical trials or on regulatory documents. The research team investigated over 400,000 posts on the social media platform Reddit from more than 67,000 users and found symptoms relating to the reproductive system, such as menstrual changes, fatigue, and temperature-related complaints.
“Some of the side effects we found, like nausea, are well known, and that shows that the method is picking up a real signal,” says the study’s senior author, Sharath Chandra Guntuku, research associate professor in Computer and Information Science (CIS) at Penn Engineering, University of Pennsylvania, US.
“The underreported symptoms are leads that came from patients themselves, unprompted, and clinicians could potentially pay attention to them.”
Commonly reported side effects include gastrointestinal symptoms such as nausea, vomiting, and diarrhea, which have all been established in clinical trials and regulatory documents and have been extensively reported on. The nutrition industry has developed various GLP-1 companion products to help users alleviate some of these well-known issues.
However, the new study leverages data from social media to capture a broader range of experiences from GLP-1 users, including semaglutide and tirzepatide, that are not yet fully explored in the pharmaceutical and nutrition industries. It aims to provide a more comprehensive safety profile using real-world data for clinicians and regulators.
Using real-world data
The study has been published in Nature Health and investigated data from 410,198 Reddit posts by 67,008 users, between May 2019 and June 2025.
The most symptoms reported represent those already known from clinical trials, gastrointestinal issues, as reported by 43.5% of users. Nutrition Insight recently sat down with experts to discuss how the industry can bridge this gap in digestive health.
Among users of both semaglutide and tirzepatide, the study details that 36.9% reported nausea, 16.7% fatigue, 16.3% vomiting, 15.3% constipation, and 12.6% diarrhea.
Unknown side effects included intermenstrual bleeding, heavy bleeding, and irregular menstrual cycles.Psychiatric symptoms were reported by 12.9% of users, including 4.2% reporting anxiety and 2.8% depression.
However, 4% reported unknown side effects of reproductive symptoms, including intermenstrual bleeding, heavy bleeding, and irregular menstrual cycles. Other observations were reports of temperature-related complaints, including chills, feeling cold, hot flashes, and fever-like symptoms.
GLP-1 drugs decrease users’ appetite, which experts previously flagged can lead to micronutrient deficiencies and loss of lean muscle mass. This creates a need for nutritional guidance when using these drugs.
Need for further research
Since the study is not causal, the authors cannot conclude that GLP-1 drugs are the cause of these symptoms.
“But nearly 4% of the Reddit users in our sample reported menstrual irregularities, which would be even higher in a female-only sample. We think that’s a signal worth investigating,” says Neil Sehgal, the study’s first author and a doctoral student in CIS at the University of Pennsylvania.
Reddit is a male-dominated platform, say the researchers, and it is mainly used by younger people, which does not make this sample representative of the entire population. An additional limitation is that global GLP-1 users may not be represented, as a large part of Reddit users are based in the US.
The study notes that despite these limitations, social media is still a useful tool to investigate under-reported effects.
“Clinical trials generally identify the most dangerous side effects of drugs,” adds Lyle Ungar, professor in CIS at the University of Pennsylvania, and a co-author on the study. “But they can fail to find what symptoms patients are most concerned about; even though social media is not necessarily representative, a large collection of posts may reflect additional concerns.”