Wegovy and Mounjaro: What's the Difference?

The most fundamental difference is the active substance and the receptors each medicine acts on.

Active substances

• Wegovy contains semaglutide, a GLP-1 receptor agonist. It works by mimicking the hormone GLP-1, which is involved in appetite regulation and feelings of fullness.
• Mounjaro contains tirzepatide, a dual GIP and GLP-1 receptor agonist. It acts on both the GLP-1 and GIP pathways simultaneously.

Dose comparison

Both medicines are started at a low dose and increased gradually — the pace and extent of any dose change is always decided by your prescriber, not by you. Commonly referenced dose strengths are:

• Wegovy (semaglutide): 0.25 mg, 0.5 mg, 1 mg, 1.7 mg, and 2.4 mg once weekly
• Mounjaro (tirzepatide): 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg once weekly

The dose figures are not directly comparable between the two medicines — they use different units and receptor targets, so a higher number on one does not mean a stronger or weaker effect relative to the other.

Washout period between Wegovy and Mounjaro

If your prescriber is considering switching you from one medicine to the other, they will advise on any gap or washout period required. This is a clinical decision based on your individual history — never stop, start, or switch either medicine without guidance from your prescriber or doctor.

Side-effect profiles

Both medicines share a broadly similar pattern of commonly reported side effects, particularly gastrointestinal ones: nausea, vomiting, diarrhoea, constipation, and indigestion are reported with both. This is consistent with their shared action on GLP-1 pathways. As with all medicines, individual experience varies. For a more detailed side-by-side look, see our full Wegovy vs Mounjaro comparison.

Both Wegovy and Mounjaro carry a black triangle (▼) in the UK, meaning they are subject to additional monitoring. Any side effects should be reported to your healthcare professional and to your national reporting scheme (such as the UK's Yellow Card scheme).

For broader context on tirzepatide, including how it is used and what to expect, visit our Mounjaro guide. If you have questions about combining either medicine with other substances, our page on codeine and Mounjaro interactions covers one commonly asked example.

GLP Trackr is built for people already prescribed either Mounjaro or Wegovy — the app supports both medicines and adapts to your dose and schedule.

Because both are once-weekly injections with gradual dose titration, dose logging is one of the most immediately useful features. Every injection can be recorded with the date, dose strength, and injection site, so you always have a clear record of where you are in your schedule. The app can also send gentle dose reminders, so a weekly shot is never accidentally missed.

If you are switching between medicines — or have questions you want to raise at your next appointment — the side-effect tracker lets you log how you feel day to day and spot patterns over time. That log can be a genuinely useful reference to bring to your prescriber, rather than trying to recall weeks of experience from memory.

If you are currently pregnant or thinking about becoming pregnant, the decision about whether to continue either medicine is one for your prescriber — our page on pregnancy and Mounjaro outlines why this warrants a prompt conversation with your healthcare team.

Always follow your prescriber's or doctor's guidance on dose, timing, and any switch between medicines — they have the full picture of your health history. If you experience symptoms that are severe, persistent, or worrying, contact your healthcare professional promptly rather than waiting for your next scheduled appointment.

Ready to bring your Mounjaro or Wegovy journey into one clear view? GLP Trackr is available free on the App Store and Google Play, with a 7-day free trial to get started — log your doses, track how you feel, and carry a record into every prescriber conversation.