Penn AI study of 400,000 Reddit posts flags menstrual and temperature reports among GLP-1 users
The study cannot show the drugs caused these symptoms, but researchers say the online reports of menstrual changes and temperature shifts are leads worth investigating.
A University of Pennsylvania team used artificial intelligence to analyze more than 400,000 Reddit posts from nearly 70,000 people taking semaglutide (Ozempic, Wegovy and Rybelsus) and tirzepatide (Mounjaro and Zepbound), according to a study published in Nature Health [1]. Gastrointestinal symptoms were the most common complaints, but the analysis also turned up frequent mentions of menstrual changes and body-temperature shifts that researchers say deserve closer study [1].
The project looked at more than five years of posts written in online GLP-1 communities [1]. About 44% of the users included described at least one side effect [1]. Digestive problems, including nausea, were the most common category, which matched what is already known about these drugs and gave the researchers confidence that the method was detecting real patterns, said Sharath Chandra Guntuku, a research associate professor at Penn Engineering and the study's senior author [1].
Nearly 4% of users who reported side effects described reproductive symptoms. Those included bleeding between periods, heavy bleeding and irregular menstrual cycles [1].
"We can't say that GLP-1s are actually causing these symptoms," said Neil Sehgal, the study's first author and a doctoral student in computer and information science. "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." [1]
A second cluster involved body temperature: chills, feeling unusually cold, hot flashes and symptoms resembling a fever [1]. Fatigue was the second most frequently reported complaint in the data, even though relatively few clinical trials reported fatigue often enough for it to reach established reporting thresholds [1].
The researchers used large language models such as GPT and Gemini to sort everyday descriptions into standardized medical categories, including terminology from the Medical Dictionary for Regulatory Activities [1]. Guntuku described the approach as "computational social listening" [1].
One reason the menstrual and temperature reports drew attention is that GLP-1 drugs are thought to work by engaging the hypothalamus, a brain region that helps regulate hunger, hormones, reproduction and body temperature, said Jena Shaw Tronieri, a senior research investigator at Penn's Center for Weight and Eating Disorders and a co-author [1]. "That doesn't mean the medications are necessarily causing these symptoms, but it could suggest that reports of menstrual changes and body temperature fluctuations are worth studying more systematically," she said [1].
The analysis has limits. Reddit users tend to be younger, are more likely to be male, and are disproportionately located in the United States, so they do not represent everyone taking these drugs [1]. "We don't really know yet whether what we're seeing on Reddit reflects the experience of GLP-1 users globally, or whether it's particular to the kind of person who posts on Reddit in the United States," said Lyle Ungar, a Penn computer science professor and co-author [1].
The authors reported no outside funding. Tronieri reported receiving an investigator-initiated grant, on behalf of the university, from Novo Nordisk, and consulting fees from Currax Pharmaceuticals [1].
Why it matters for patients
Symptoms that patients discuss with one another online may never make it into a doctor's visit or a formal safety report, the researchers note [1]. That means the experiences most on patients' minds are not always the ones captured in drug labels or in trial data.
The study does not show that semaglutide or tirzepatide caused any of these symptoms, and it does not establish how common menstrual changes or temperature problems are among all people taking the drugs [1]. How severe those symptoms are, how long they last, and whether they resolve have not been reported. What the researchers say they have is a set of leads that came from patients themselves [1].
What happens next
The team wants to extend the work beyond Reddit and beyond English-language communities, to see whether the same patterns show up among different groups of people and on other platforms [1]. No timeline for that work has been disclosed [1]. No regulatory action based on the findings has been reported [1].
Sources
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