Overview
Every medication affects people differently, so it's natural to notice some changes when moving from Mounjaro® (tirzepatide) to Wegovy® (semaglutide). Although both belong to the same class of medications — GLP-1 receptor agonists — they work in distinct ways in your body, so switching between them can feel different.
Use this article when you want to:
Understand how your body adapts to a new active ingredient after switching from Mounjaro® to Wegovy®
Learn about the washout week between medications and its purpose
Find out how to stay on track during your first month on Wegovy®
How Does Wegovy® Work Differently to Mounjaro® in Your Body?
Even though both medications target appetite, Wegovy® (semaglutide) and Mounjaro® (tirzepatide) work differently at a cellular level:
Wegovy®: mimics one hormone, GLP-1, to regulate fullness and blood sugar.
Mounjaro®: mimics two hormones, GLP-1 and GIP, which can sometimes provide a stronger metabolic signal.
When you switch from Mounjaro® to Wegovy®, your body is adapting to a new medication with a different mechanism of action. You may notice subtle differences in how quickly you feel full, the types of food you crave, or your daily energy levels. These are all signs of your body adjusting to Wegovy®'s single-hormone approach.
What Is the "Washout" Week Between Mounjaro® and Wegovy®?
To help ensure a safe transition, you must wait 7 days after your final Mounjaro® dose before taking your first Wegovy® injection. This gap is often called a "washout" period. It prevents the two medications from overlapping in your system, which is intended to reduce the risk of severe nausea or vomiting during the switch.
During this washout week, you might notice:
Return of appetite: as Mounjaro® wears off, your "food noise" may temporarily return.
Minor weight fluctuations: it's common to see a small increase of around 0.5–1.5kg, due to water retention or a temporary increase in food intake. This usually reverses once Wegovy® takes effect.
How Do I Keep My Results on Track After Switching to Wegovy®?
MedExpress matches you to a personalised Wegovy® starting dose and supports you through the change, so your progress can keep moving forward. To help keep your results on track:
Maintain your habits: the healthy routines you built on Mounjaro®, such as high-protein meals and regular movement, are your strongest tools during the switch to Wegovy®.
Monitor your response: pay attention to how you feel in the 48 hours following your first Wegovy® dose.
Be patient: it can take 2–4 weeks for Wegovy® to reach a steady level in your system. If weight loss feels slightly slower at first, remember you're building toward long-term, sustainable results.