What is Mounjaro®?
Mounjaro® is a once-weekly injection containing the active ingredient tirzepatide. It is used for weight management and can also be used to treat type 2 diabetes.
Mounjaro® works by acting on two hormone pathways in the body: GIP and GLP-1. These are involved in appetite, feelings of fullness and blood sugar regulation.
When used for weight management, Mounjaro® should be used alongside appropriate changes to diet and physical activity.
Mounjaro® vs Wegovy®
Mounjaro® and Wegovy® are both once-weekly injectable treatments used for weight management, but they contain different active ingredients and work slightly differently.
Wegovy® contains semaglutide and acts on GLP-1 receptors.
Mounjaro® contains tirzepatide and acts on both GIP and GLP-1 receptors.
Both treatments are gradually increased through different dose strengths. This process is known as titration and helps your body adjust to the medication.
Both medications can cause side effects, particularly gastrointestinal side effects such as nausea, vomiting, diarrhoea, constipation and abdominal discomfort.
For detailed information about side effects, please see the Patient Information Leaflet supplied with your medication or our dedicated side-effect guidance.
How effective are Mounjaro® and Wegovy®?
Clinical studies have shown significant weight loss with both treatments when used alongside appropriate lifestyle changes.
Clinical trial data has shown average body weight reductions of approximately 22.5% with Mounjaro® 15mg and around 21% with Wegovy® 7.2mg in relevant study populations.
Individual results will vary. The amount of weight you lose can depend on factors including your dose, response to treatment, tolerance, diet and physical activity.
Why might I switch from Wegovy® to Mounjaro®?
There are several reasons why you may consider changing weight management treatment, including:
- Your response to your current treatment
- Side effects
- Treatment availability
- Cost
- Your individual treatment goals
Changing treatment does not guarantee that you will lose more weight or experience fewer side effects.
Your response to Mounjaro® may be different from your response to Wegovy®, so treatment should be selected according to your individual circumstances and clinical suitability.
How do I switch from Wegovy® to Mounjaro®?
If you are currently taking Wegovy® and would like to switch to Mounjaro®, you do not always need to restart Mounjaro® at its lowest 2.5mg dose.
Our clinical team has developed switching guidance based on your current Wegovy® dose.
Recommended switching doses
| Current Wegovy® dose | Recommended Mounjaro® dose |
|---|---|
| 0.25mg | 2.5mg |
| 0.5mg | 2.5mg |
| 1mg | 2.5mg |
| 1.7mg | 2.5mg |
| 2.4mg | 5mg |
| 7.2mg | 5mg |
These are recommended switching doses only. You may be able to select a lower dose, and the prescribing clinician will make the final decision on whether your chosen treatment and dose are clinically appropriate.
How long should I wait between Wegovy® and Mounjaro®?
A 7-day break is recommended between your last Wegovy® injection and your first Mounjaro® injection.
For example, if you take your final Wegovy® injection on a Monday, you would usually take your first Mounjaro® injection the following Monday.
Do not use Wegovy® and Mounjaro® at the same time.
What if I've had a break from Wegovy®?
If you have already had a significant break from treatment, the dose you can switch to may be different.
Our break-in-treatment guidance takes priority over the standard switching guidance.
If your treatment break means that you need to restart at a lower Wegovy® dose, this restart dose will be used to determine the appropriate Mounjaro® switching dose.
If you are required to restart treatment, you must do so at the recommended starting dose.
Do I need to gradually stop Wegovy® before switching?
If you are switching directly from Wegovy® to Mounjaro®, follow the switching instructions provided by your prescriber.
The standard switching guidance recommends a 7-day break after your last Wegovy® injection before starting Mounjaro®.
You should not take additional Wegovy® doses, gradually reduce your dose yourself or overlap Wegovy® and Mounjaro® unless specifically instructed to do so by a healthcare professional.
Starting Mounjaro® after Wegovy®
The Mounjaro® dose you start on will depend on your current Wegovy® dose, any treatment breaks and your individual circumstances.
Patients switching from Wegovy® 0.25mg, 0.5mg, 1mg or 1.7mg will generally be recommended Mounjaro® 2.5mg.
Patients switching directly from Wegovy® 2.4mg or 7.2mg may be recommended Mounjaro® 5mg.
Once you have switched, any future dose increases should follow the appropriate Mounjaro® dosing schedule and the advice of your prescriber.
Do not increase your Mounjaro® dose yourself.
Important information
The switching doses above are designed to support a safe transition between treatments and reduce the risk of side effects. They should not be interpreted as exact dose-for-dose equivalents.
Your prescribing clinician will make the final decision based on your medical history, current treatment, treatment breaks, side effects and how well you have tolerated your medication.
If you are unsure which dose is appropriate when switching, please contact our clinical team for advice.