6 ‘Hidden’ Side Effects of GLP-1 Weight Loss Drugs

• A recent study found various “hidden” side effects of GLP-1 drugs like Ozempic, including chills, hot flashes, and irregular periods.
• The researchers used self-reported Reddit data to examine the real-world effects of these medications.
• An expert weighs in on why hidden side effects, such as Ozempic chills, may occur.

GLP-1 medications, like Ozempic, Wegovy, and Mounjaro, have various known side effects, including nausea, fatigue, constipation, and diarrhea.

However, a recent study published in Nature Health found that GLP-1 drugs may also come with certain “hidden” side effects.

The researchers analyzed 410,198 Reddit posts that mentioned either semaglutide or tirzepatide. They found a total of 67,008 users who self-reported using these medications. Of those, 43.5% posted about at least one side effect.

Reproductive issues, such as menstrual irregularities and temperature-related complaints, like chills and hot flashes, were the most notable unrecognized side effects of GLP-1s.

Jeffrey Lee, MD, a double board-certified plastic surgeon and founder of JL Plastic Surgery in Boston, MA, who was not involved in the study, spoke to Healthline about these “hidden” side effects, why they may occur, and what people may misunderstand about GLP-1s from social media posts.

This interview has been lightly edited and condensed for clarity and length.

Lee: The most common side effects I see in practice are gastrointestinal, things like nausea, bloating, or constipation.

These are typically temporary and often dose-dependent, meaning they can improve over time or with a dosage adjustment.

Of the lesser-known side effects mentioned in the study, I have occasionally had patients report fatigue, but it’s not something I see frequently.

I have not personally seen most of the other symptoms highlighted in the study in a consistent or clinically significant way.

Lee: GLP-1 agonists primarily affect the gastrointestinal system, but they also act on the brain, particularly the hypothalamus, which regulates many core functions, including hormones, temperature, and appetite.

Because of this, it’s plausible that some patients could experience broader systemic effects, including hormonal or temperature-related symptoms.

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.

Clinically, we are seeing that some patients report a reduced sense of reward from certain behaviors.

For example, there have been reports of individuals with alcohol use issues experiencing a decreased urge to drink. This suggests that GLP-1s may blunt the reward response, which could be beneficial in some contexts.

However, that same mechanism may also translate into a dampening of emotional highs and lows, which some patients may interpret as apathy or decreased libido. This is still an emerging area of research, but it’s one of the more interesting potential effects of these medications.

Lee: Patient behavior can absolutely play a role.

If someone is actively restricting intake beyond what the medication is already doing, they may experience symptoms like irritability or mood swings.

On the other hand, if a patient is fully reliant on the medication and experiences little to no hunger, those fluctuations may be less noticeable.

So there’s often an interplay between the medication’s effects and the patient’s behavioral response.

Lee: One of the biggest challenges with social media is that it captures anecdotal, self-reported experiences without context.

It can be difficult to determine whether a symptom is directly caused by the medication, related to rapid weight loss, influenced by other medications, or tied to underlying health conditions.

Without that clinical context, it’s easy for associations to be made that aren’t necessarily causal. That’s why it’s important to interpret these reports carefully and in conjunction with clinical data.

Lee: These limitations are significant. For findings to be broadly applicable, the study population needs to reflect real-world patients in terms of age, gender, medical history, and dosing.

Self-reported data, especially from platforms like Reddit, can introduce bias, as it often captures a narrower or more vocal subset of users.

That said, studies like this can still be valuable as an early signal. They can help generate hypotheses and guide more rigorous, controlled research that allows us to draw more definitive conclusions.