Wegovy vs Mounjaro Side Effects: What the Differences Look Like in Practice

Wegovy contains semaglutide, a GLP-1 receptor agonist. Mounjaro contains tirzepatide, a dual GIP and GLP-1 receptor agonist — meaning it acts on two appetite-regulating pathways rather than one. Both medicines are taken as once-weekly injections and are prescription-only.

Commonly reported side effects with both medicines

• Gastrointestinal effects: nausea, vomiting, diarrhoea, constipation, indigestion, reflux, and burping are frequently reported with both Wegovy and Mounjaro, particularly in the early weeks or after a dose increase.
• Fatigue and headache: both medicines list these among commonly reported effects.
• Injection-site reactions: mild redness or discomfort at the injection site can occur with either.
• Reduced appetite: often described as lowered "food noise" — a commonly reported effect of both medicines that tends to be most noticeable early on.

Where the profiles can differ

Because tirzepatide (Mounjaro) also acts on GIP receptors, some researchers and clinicians note differences in tolerability patterns, though both medicines carry broadly similar gastrointestinal risks according to their respective product information. Individual experience varies considerably — some people find one medicine easier to tolerate than the other, but this cannot be predicted in advance. Comparisons such as Wegovy vs tirzepatide are best discussed with your prescriber using your own health history as the starting point.

Medicines not covered in detail here

You may have seen comparisons involving other medicines — such as Wegovy vs Saxenda (liraglutide, an older daily-injection GLP-1), Wegovy vs Orlistat (a non-injectable weight-management medicine), or the emerging investigational compound retatrutide. These are distinct treatments; any questions about their suitability belong with your prescriber.

For a broader look at how these two medicines compare overall, see our Wegovy vs Mounjaro full comparison. If cost considerations are relevant to you, our page on the cost factors around Wegovy and Mounjaro covers that topic without quoting prices. You can also read about how Wegovy compares to Ozempic, another semaglutide-based medicine.

Both Wegovy and Mounjaro carry a black triangle (▼) status in some territories, meaning healthcare professionals and patients are encouraged to report side effects through their national scheme (such as the UK's Yellow Card scheme, or the equivalent in your country).

Whether you have been prescribed Wegovy or Mounjaro, one of the most useful things you can do is keep a consistent record of how you feel — especially in the first weeks or after any dose adjustment. GLP Trackr's side-effect tracking feature lets you log symptoms as they happen, note their severity, and see patterns emerge over time. That log becomes a practical resource to bring to your next prescriber appointment rather than relying on memory.

Alongside side-effect logging, the app's daily check-in captures energy, mood, sleep, and food noise in around 30 seconds each morning — useful context when you are trying to understand whether a rough day is medication-related or influenced by something else entirely. The insights and analytics tools can surface correlations in your own data, such as whether nausea tends to cluster in the days immediately after your weekly injection.

GLP Trackr supports both Wegovy and Semaglutide users and Mounjaro and tirzepatide users — the tracking features work the same way regardless of which medicine you have been prescribed.

GLP Trackr is a tracking and journaling app; it does not replace the guidance of your prescriber or doctor. If you are experiencing side effects that are severe, persistent, or worrying, contact your healthcare professional promptly. Any decisions about your dose or your medicine should be made with your prescriber — never on your own.

Ready to start logging your experience? GLP Trackr is free to try for seven days — available now on the App Store and Google Play.