Nearly half of GLP-1 medication users who posted on Reddit about their experience reported at least one side effect, including some that rarely appear in clinical literature. A new study published in a peer-reviewed journal found that among 67,008 self-reported users of semaglutide or tirzepatide, 43.5% mentioned side effects. The most notable lesser-known ones: temperature-related complaints like chills and hot flashes, and reproductive issues including menstrual irregularities.
The researchers drew from 410,198 Reddit posts mentioning either semaglutide, the active ingredient in Ozempic and Wegovy, or tirzepatide, sold as Mounjaro. The scale of that dataset gave the study unusual reach, capturing patient experiences that don't always make it into doctors' offices or formal reporting systems.
The known side effect profile of GLP-1 drugs centers on the gut: nausea, bloating, constipation, and diarrhea. Those remain the most common complaints in clinical practice. But the Reddit analysis flagged a broader range of systemic effects that warrant closer examination, according to experts.
Jeffrey Lee, a double board-certified plastic surgeon in Boston who was not involved in the study, told Healthline that the findings are plausible given how these drugs work. GLP-1 agonists don't just act on the digestive system. They also target the hypothalamus, a region of the brain that regulates body temperature, hormones, and appetite. That dual action could explain why some patients report temperature fluctuations or hormonal disruptions, even if those effects are not yet well-established clinically.
"Because of this, it's plausible that some patients could experience broader systemic effects, including hormonal or temperature-related symptoms," Lee said. "That said, these effects are not yet well established clinically, and more research is needed to determine whether they are directly caused by the medication or influenced by factors such as weight loss, metabolic changes, or individual physiology."
One of the more striking areas of emerging research involves the brain's reward system. GLP-1 drugs appear to influence dopamine signaling, which governs how the brain processes pleasure and motivation. Clinically, some patients have reported reduced cravings for alcohol or addictive behaviors, which researchers have noted with interest. But Lee pointed out a potential downside to that same mechanism.
"That same mechanism may also translate into a dampening of emotional highs and lows, which some patients may interpret as apathy or decreased libido," he said. The effect on mood and motivation is still being studied and is not yet confirmed as a direct drug effect.
The reliance on Reddit data is both a strength and a limitation of the study. Social media posts allow researchers to capture real-world experiences at scale, including from patients who may not report symptoms to their prescribers. But self-reported data can't confirm diagnoses, rule out confounding factors, or establish causation. Weight loss itself produces hormonal and metabolic changes that could account for some of the symptoms users attributed to the medication.
Menstrual irregularities, for instance, are a known consequence of significant weight change and are not necessarily a direct pharmacological effect of GLP-1 drugs. The same uncertainty applies to fatigue and temperature sensitivity, both of which can follow from rapid shifts in body composition.
Lee noted that he occasionally sees patients report fatigue but has not observed most of the other highlighted symptoms in a consistent or clinically significant way in his own practice. Still, the study adds pressure on researchers and prescribers to pay closer attention to the full range of patient-reported experiences as these medications continue to be prescribed at a large scale.
