Mounjaro or Wegovy: What Is the Difference?

Mounjaro and Wegovy are distinct medicines with different active substances and mechanisms of action, though both belong to the broader family of GLP-1-based treatments.

Active substance and mechanism

• Wegovy contains semaglutide, a GLP-1 receptor agonist. It works by mimicking the GLP-1 hormone, which plays a role in appetite regulation and the feeling of fullness after eating.
• Mounjaro contains tirzepatide, which acts on both GLP-1 and GIP receptors — making it a dual agonist. GIP is a second gut hormone also involved in appetite and metabolism.

Whether that dual mechanism makes a meaningful clinical difference for any particular person is a question for your prescriber, not something this page can answer.

How they are taken

Both medicines are injected once a week using pre-filled pen devices. Both are typically started at a lower dose and adjusted over time under prescriber guidance. The available dose strengths differ between the two — your prescriber or pharmacist can advise on the specific pen options for whichever medicine you have been prescribed.

Side-effect profiles

The most commonly reported side effects for both medicines are gastrointestinal — nausea, constipation, diarrhoea, indigestion, and reflux appear frequently in reported experience for both tirzepatide and semaglutide. Whether side effects feel more or less noticeable varies between individuals and cannot be predicted in advance. If you are wondering how people compare their experience on each medicine, individual responses differ considerably. Any side effects that are severe, persistent, or worrying should be discussed with your healthcare professional promptly, and reported to your national pharmacovigilance scheme (such as the UK Yellow Card scheme) where applicable.

Both medicines carry a black triangle (▼) designation in some markets, meaning they are subject to additional monitoring. You can find full prescribing information for each via the electronic Medicines Compendium (eMC).

Are they the same thing?

No — Mounjaro (tirzepatide) and Wegovy (semaglutide) are different medicines with different active substances. Tirzepatide is sometimes referred to loosely as a GLP-1 medicine, but it is more precisely a dual GIP and GLP-1 receptor agonist. For a closer look at what the evidence says about effectiveness, your prescriber is the right person to interpret that in the context of your own health. You may also find it useful to read about how Ozempic and Wegovy compare, since both contain semaglutide but are licensed for different purposes.

GLP Trackr is built for people already on Mounjaro or Wegovy — the app supports both medicines equally, and which one you have been prescribed does not change how you use it.

The most relevant feature for someone thinking about this comparison is the side-effect tracker. Since gastrointestinal symptoms are commonly reported on both medicines, being able to log what you experience — and when — gives you a clear, dated record to bring to your next prescriber appointment rather than relying on memory. Over time, the app helps you spot whether symptoms cluster around injection day, ease at certain dose stages, or correlate with food or sleep patterns.

Alongside that, dose and injection logging keeps your weekly schedule on track whichever pen you are using — every dose, site, and date in one place, with reminders so a weekly injection is never forgotten.

The choice between Mounjaro and Wegovy is your prescriber's to make with you — but once you are prescribed, staying consistent and informed is where GLP Trackr helps. For a broader look at how the two medicines are discussed, visit our Wegovy vs Mounjaro overview.

GLP Trackr is free to try for seven days — available on the App Store and Google Play. Log your first dose, start tracking how you feel, and arrive at your next appointment with real data to share.