A new study published in JAMA Network Open used artificial intelligence to analyze nearly 150,000 Reddit posts and comments from around 40,000 users discussing retatrutide, an experimental weight-loss drug that has not been approved by regulators. Researchers at the University of Pennsylvania describe it as the first systematic look at symptoms reported by people claiming to use unapproved versions of the compound.

Retatrutide belongs to the newer generation of GLP-1 medications aimed at appetite and body weight regulation. Semaglutide acts on one hormone receptor involved in blood sugar control and appetite, tirzepatide targets two, and retatrutide activates three, which the authors say could produce a different combination of effects throughout the body.

Key results

From the full set of posts, the team identified roughly 14,000 users who said they had personally taken an unapproved version of the drug. After excluding expected effects such as weight loss and reduced appetite, 7,823 users reported at least one symptom that could be classified in standardized medical terms.

Among those, increased appetite was the most frequently described classifiable symptom. That is the opposite of what the drug is designed to do, and it diverges from Phase 2 trials, where gastrointestinal complaints including nausea were the most common side effects.

How this set differs from earlier GLP-1 chatter

Compared with the team's earlier analysis of more than 400,000 posts about semaglutide and tirzepatide, the retatrutide discussions carried proportionally more mentions of appetite changes, sleep disturbances, increased heart rate, and muscle-related symptoms. Nausea and other digestive complaints were proportionally less common.

Limitations

The researchers are blunt that this is not proof of unknown side effects. "We can't say that retatrutide is causing these symptoms, or even that Reddit users are actually taking genuine retatrutide, since the drug is not legally available, and gray market formulations vary," says co-author Lyle Ungar.

People willing to buy an unapproved medication also differ from trial participants, and co-author Jena Shaw Tronieri notes some may be taking multiple experimental peptides at once. Self-reported posts cannot establish causation.

Where the signal goes next

The value here is hypothesis generation, not safety conclusions, and the team is clear about that. Retatrutide is in Phase 3 trials, and whether these patterns hold up depends on other researchers testing them in entirely different datasets.