What if your doctor's best source of information isn't a clinical trial — it's a comments section? A team at the University of Pennsylvania decided to find out. They fed more than 400,000 Reddit posts, written by nearly 70,000 users over five years, into an AI system trained to spot patterns in the way people describe their own bodies. The subject: GLP-1 drugs, the blockbuster weight-loss and diabetes medicines sold as Ozempic, Wegovy, Mounjaro, and others.

The results, published in *Nature Health*, were surprising enough to deserve a second look. The AI confirmed some well-known side effects, like nausea — which is actually encouraging, because it suggests the method is detecting something real. But it also surfaced two categories of symptoms that rarely appear in official regulatory documents. The first involves reproductive health: users reported noticeable changes in their menstrual cycles.

The second involves body temperature: chills, hot flashes, and similar sensations that patients described in their own unprompted words. Nearly 4% of all Reddit users in the sample mentioned menstrual irregularities, a figure that would be even higher if measured among female users alone. The researchers are careful about what they are claiming. "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," said Neil Sehgal, the study's first author and a doctoral student at Penn Engineering.