Switching from Mounjaro to Wegovy: What Happens to Your Dosage?

Mounjaro is a dual GIP and GLP-1 receptor agonist (active substance tirzepatide), while Wegovy is a GLP-1 receptor agonist alone (active substance semaglutide). Because they work differently and have different dose strengths, there is no simple one-to-one dose conversion between them. Prescribers typically start people at a lower dose of the new medicine — even if they had been on a higher dose of the previous one — to let the body acclimatise.

Side effects that can emerge or re-emerge during a switch

The titration phase of any GLP-1 medicine is often when gastrointestinal side effects are most noticeable. When switching medicines, some people effectively re-enter a titration period. Commonly reported effects include:

• Nausea and indigestion — GLP-1 receptor agonists slow gastric emptying, and a new medicine can make this feel more pronounced again initially.
• Fatigue and headache — often reported in the first days after a dose change or medicine change.
• Diarrhoea or constipation — bowel habits can shift as the body responds to a different active substance.
• Injection-site reactions — Wegovy pens are different devices; some people notice localised redness or tenderness at first.

These effects are commonly reported and often ease as the body settles, but they are not universal and their severity varies from person to person. If anything feels severe, persistent, or out of the ordinary, contact your healthcare professional promptly — do not wait for a scheduled appointment.

For broader context on side effects during any stage of treatment, the Mounjaro side effects guide covers the most commonly reported experiences and how to approach them. You may also find it useful to read about what the switch from Mounjaro to Wegovy generally involves or the practical steps people take when making this change. If your prescriber is considering semaglutide in a different form, information on switching from Mounjaro to Ozempic may also be relevant.

The side-effect tracker in GLP Trackr is particularly useful during a medicine switch. You can log each symptom — nausea, fatigue, digestive changes, injection-site reactions — and see how the pattern changes day by day and after each dose. Over a few weeks, that log becomes a clear, timestamped record of how your body responded to the new medicine and dose level, which is genuinely helpful to share at your next prescriber appointment.

Alongside side-effect logging, you can use the dose-logging feature to record each Wegovy injection — including the dose strength and date — so there is never any ambiguity about where you are in your schedule. GLP Trackr also offers a doctor report feature that compiles your tracked data into a summary you can bring to consultations, making it easier to have an informed conversation about how the switch is going.

GLP Trackr helps you record what you are experiencing so you can discuss it with your prescriber — it is not a substitute for their clinical guidance, and any decision about dose or medicine should always be made with them, not alone.

Log your symptoms, doses, and how you feel throughout the transition. GLP Trackr is free to try for 7 days — available on the App Store and Google Play.