Can You Switch from Mounjaro to Wegovy?

Mounjaro and Wegovy are both prescription-only, once-weekly injectable medicines used in weight management, but they act on different receptors. Mounjaro's active substance, tirzepatide, targets two pathways — GLP-1 and GIP receptors. Wegovy's active substance, semaglutide, targets GLP-1 receptors only. Because the mechanisms differ, your body's response — including any side effects you experience — may change when switching.

Side effects to be aware of during a switch

Both medicines share a similar side-effect profile. Gastrointestinal symptoms such as nausea, vomiting, diarrhoea, constipation, and indigestion are commonly reported with each. However, many people find that side effects they had adapted to on one medicine can return or shift in intensity when starting a new one — particularly during the initial weeks at a new starting dose. Fatigue, headache, and injection-site reactions are also commonly reported across both.

Because a prescriber-led switch typically involves restarting at a lower dose of the new medicine, some of the adjustment-period symptoms that are common at the beginning of treatment may reappear. This is not unusual, though if anything feels severe or persistent, it is important to contact your healthcare professional promptly.

What about switching to Ozempic?

Some people also ask about switching from Mounjaro to Ozempic — Ozempic also contains semaglutide but is licensed for a different indication. Whether that is appropriate for you is again a matter for your prescriber. The side-effect considerations are broadly similar to those described above.

For a fuller look at the practical side of making this change, see our guide on switching from Mounjaro to Wegovy, and for a detailed breakdown of how the two medicines compare, our page on moving between Mounjaro and Wegovy covers the key differences. Both medicines also carry additional monitoring requirements — any side effects worth noting can be reported to your national reporting scheme (such as the UK's Yellow Card scheme) as well as to your healthcare professional.

A period of change — whether that means new side effects, a different appetite pattern, or a fresh adjustment phase — is exactly when consistent tracking matters most. GLP Trackr's side-effect tracker lets you log symptoms day by day, so you can see whether nausea, fatigue, or digestive discomfort follows a pattern tied to your injection day or gradually eases over time. That kind of record is genuinely useful to bring to your prescriber rather than relying on memory alone.

The app also lets you log each dose and injection site, which is particularly relevant when restarting at a new strength on a different medicine. Keeping a clear record of dates, doses, and how you felt in the days that followed gives you and your prescriber a shared, factual picture of how the transition is going.

GLP Trackr also generates a doctor report you can share at appointments — a clear summary of your logged symptoms, weight trend, and injection history, so your consultations are grounded in your actual data rather than estimates.

For a broader understanding of what to expect on Mounjaro, the Mounjaro side effects guide covers the full range of commonly reported experiences and how to approach them.

Important: GLP Trackr helps you record and organise your experience — it is not a substitute for clinical advice. Any decision about switching medicines, adjusting a dose, or managing symptoms should be made with your prescriber or doctor, who knows your full history. If you experience anything severe, persistent, or worrying during or after a switch, contact your healthcare professional without delay.

Start logging your symptoms and tracking how your body responds — download GLP Trackr on the App Store or Google Play and explore it free for 7 days.