If you are searching for a Mounjaro to Wegovy dose conversion chart, there is an important point to know: there is no validated clinical conversion between these two medicines.
Mounjaro contains tirzepatide, while Wegovy contains semaglutide. Because they contain different active ingredients and work in different ways, there is no reliable formula that can tell you that a particular Mounjaro dose is equivalent to a particular Wegovy dose.
For example, there is no clinically established calculation that says "7.5mg Mounjaro equals X mg Wegovy". This also applies if you are comparing Zepbound with Wegovy. Zepbound is the US brand name for tirzepatide used for weight management, while Mounjaro also contains tirzepatide.
If you are thinking about switching from one medicine to the other, the decision should be based on your individual circumstances and made with a healthcare professional. This page explains why there is no conversion chart, what switching can involve, and the separate dosing schedules for both medicines.
Key things to know
- Mounjaro contains tirzepatide, while Wegovy contains semaglutide
- Mounjaro acts on both GIP and GLP 1 receptors, while Wegovy acts on the GLP 1 receptor
- There is no validated milligram for milligram conversion between Mounjaro and Wegovy
- Zepbound contains the same active ingredient as Mounjaro, tirzepatide, so the same conversion issue applies when comparing it with Wegovy
- Switching between the medicines should be discussed with a healthcare professional who can consider your individual circumstances
- Mounjaro and Wegovy each have their own dosing schedules and prescribing guidance
Why a Conversion Chart Between Mounjaro and Wegovy Cannot Be Used
Mounjaro contains tirzepatide. It works on two hormone receptors, GIP and GLP 1. Wegovy contains semaglutide, which works on the GLP 1 receptor.
Although both medicines can be used as part of weight management, they are not the same medicine. They have different active ingredients, dosing schedules and prescribing information.
This means that the milligram amounts cannot simply be compared. For example, 5mg of tirzepatide does not have a direct milligram equivalent in semaglutide.
This is different from medicines that contain the same active ingredient in different strengths, where a mathematical calculation may sometimes be possible.
If you find an online chart claiming that a specific Mounjaro dose is equivalent to a specific Wegovy dose, be cautious. There is no validated clinical conversion chart that can be used to make this decision.
What About Zepbound?
Zepbound is a US brand name for tirzepatide used for weight management. Mounjaro also contains tirzepatide.
This means that Zepbound and Mounjaro contain the same active ingredient, although their licensed uses and product information can differ by country and product.
If you are searching for a "Zepbound to Wegovy" conversion, the same principle applies. Tirzepatide and semaglutide are different active ingredients, so there is no validated dose conversion between them.
If you are reading US based information about Zepbound, check that the information applies to the UK product and prescribing guidance before using it to make a treatment decision.
Why Do People Search for a Conversion Chart?
There are several understandable reasons why someone might look for a Mounjaro to Wegovy conversion.
You may be considering a switch because of availability, cost, side effects, your treatment plan or a change in your healthcare needs. You may also want to know what dose you would take after switching.
It can be tempting to look for a simple number that tells you which Wegovy dose matches your current Mounjaro dose. However, this approach does not take into account how differently people can respond to these medicines.
Your prescriber can consider your current dose, how long you have been taking it, how you have responded, any side effects, other medicines you take and your wider medical history.
If you are considering changing from Mounjaro to Wegovy, speak to your prescriber rather than using an online conversion chart to choose your dose.
What Switching Between Mounjaro and Wegovy Actually Involves
Switching from Mounjaro to Wegovy, or from Wegovy to Mounjaro, is a clinical decision.
Your prescriber may consider your current dose, how you have tolerated treatment, your response to the medicine, other medicines you take and why you want to switch.
There is no standard Wegovy dose that automatically follows a particular Mounjaro dose. Your prescriber will decide which dose is appropriate if Wegovy is suitable for you.
Depending on your circumstances, your prescriber may recommend starting Wegovy at the usual introductory dose or another appropriate dose. The decision should be based on your individual circumstances rather than a conversion calculation.
Do not increase, reduce or change your dose yourself when switching between these medicines. If you are unsure when to start the new medicine or what dose to use, speak to your prescriber or pharmacy team.
Mounjaro's Real Dosing Schedule
| Dose | Role |
|---|---|
| 2.5mg | Starting dose |
| 5mg | First maintenance dose, if appropriate |
| 7.5mg | Dose increase, if appropriate |
| 10mg | Dose increase, if appropriate |
| 12.5mg | Dose increase, if appropriate |
| 15mg | Maximum licensed dose |
Mounjaro treatment usually starts at 2.5mg once a week. After four weeks, the dose may be increased to 5mg if appropriate.
Further increases can be made in 2.5mg steps after at least four weeks on the current dose, depending on the prescriber's assessment and how you tolerate treatment.
The maximum recommended dose is 15mg once a week.
Your prescribed dose may not follow the full schedule if your prescriber decides that a different approach is appropriate for you.
Wegovy's Real Dosing Schedule
| Weeks | Dose |
|---|---|
| 1-4 | 0.25mg |
| 5-8 | 0.5mg |
| 9-12 | 1mg |
| 13-16 | 1.7mg |
| 17 onwards | 2.4mg (maintenance) |
Wegovy usually starts at 0.25mg once a week. The dose is gradually increased, normally every four weeks, until the recommended maintenance dose is reached.
Your prescriber may recommend staying at a particular dose for longer if needed, depending on how you respond to treatment and whether you experience side effects.
Do not use the table to decide which Wegovy dose to take after Mounjaro. The schedule shows how Wegovy is normally introduced and increased, but it is not a Mounjaro to Wegovy conversion chart.
Why Genuine Trial Evidence Matters More Than a Conversion Chart
Clinical trials can help explain how Mounjaro and Wegovy performed in their respective studies, but they cannot tell you which dose of one medicine is equivalent to a dose of the other.
For example, the SURMOUNT 1 trial studied tirzepatide for weight management and reported average weight losses of 15.0% with 5mg, 19.5% with 10mg and 20.9% with 15mg after 72 weeks.
The STEP 1 trial studied semaglutide 2.4mg and reported an average weight loss of around 15% after 68 weeks.
These figures come from separate clinical trials with different study designs and groups of participants. They should therefore not be used to calculate an equivalent dose.
A later head to head study, SURMOUNT 5, compared tirzepatide with semaglutide and found greater average weight loss with tirzepatide in the study population. However, this was a comparison of the two medicines in a clinical trial, not a dose conversion study.
Clinical trial results can help you understand what medicines have shown in studies, but they cannot predict exactly how much weight an individual person will lose.
Who These Medicines Are Suitable For
Whether Mounjaro or Wegovy is suitable depends on your individual circumstances.
For weight management, eligibility can depend on factors such as your BMI, weight related health conditions, medical history and other medicines you take. Meeting a particular BMI threshold does not automatically mean that either medicine will be prescribed.
Wegovy also has an approved use for reducing the risk of certain cardiovascular events in eligible adults with established cardiovascular disease and obesity or overweight. This is a specific indication and does not mean that Wegovy is suitable for everyone with cardiovascular risk.
Neither medicine should be used during pregnancy. If you are pregnant, planning to become pregnant or breastfeeding, speak to a healthcare professional before considering treatment.
There are also other medical conditions and medicines that your prescriber needs to consider. A proper clinical assessment is therefore important before starting or switching treatment.
Storage: A Quick Comparison
Both Mounjaro and Wegovy need to be stored correctly, but their storage instructions are not necessarily identical.
Unopened pens should generally be kept refrigerated at 2 to 8°C. Do not freeze either medicine or expose it to excessive heat.
The storage instructions after removal from the fridge can differ between products and specific pen types. Always check the patient information leaflet for the medicine you have been prescribed.
If you are unsure whether your medicine has been stored correctly, speak to your pharmacy before using it.
Common Side Effects When Switching
Mounjaro and Wegovy can both cause gastrointestinal side effects. Common side effects include nausea, diarrhoea, constipation and vomiting. Headache can also occur.
Side effects may be more noticeable when starting treatment or increasing the dose. If you switch medicines, your experience may be different even if you have previously tolerated the other medicine well.
If side effects are difficult to manage or do not improve, speak to your prescriber or pharmacist. They can advise you based on your treatment and medical history.
Severe or persistent abdominal pain needs urgent medical assessment because it can be a sign of a serious condition such as pancreatitis.
Seek urgent medical help if you develop signs of a severe allergic reaction, such as difficulty breathing or swelling of the face, lips, tongue or throat.
How to Compare These Medicines Fairly Without a Conversion Chart
- Look at the individual dosing schedule for each medicine rather than trying to convert milligrams
- Consider why you are thinking about switching, such as availability, cost, side effects or your treatment plan
- Discuss your medical history and current medicines with your prescriber
- Ask your prescriber what starting dose would be appropriate if you switch
- Follow the prescribing instructions for the medicine you are given
- Do not use an online conversion chart to choose your dose
This approach gives you a more useful way to compare Mounjaro and Wegovy without treating different medicines as though their milligram strengths were interchangeable.
Getting Started with EverydayMeds
Whether you are starting treatment for the first time or considering a switch between Mounjaro and Wegovy, treatment begins with a free online clinical consultation.
Our UK registered prescribing team reviews your information and assesses whether the requested treatment is suitable for you. If treatment is prescribed, the prescriber will confirm the appropriate medicine and dose based on your individual circumstances.
All treatment is dispensed by our GPhC registered pharmacy in line with the relevant UK requirements for prescription medicines.
Medical Disclaimer
This page provides general information about Mounjaro, Wegovy and switching between these medicines. It is not a substitute for personalised medical advice.
Mounjaro and Wegovy contain different active ingredients, tirzepatide and semaglutide, and there is no validated dose conversion between them.
Do not use an online conversion chart to decide your dose. Any decision to start, stop or switch treatment should be discussed with a qualified healthcare professional who can assess your individual circumstances.
References
- Jastreboff AM, et al. Tirzepatide once weekly for the treatment of obesity. N Engl J Med. 2022;387:205-216 (SURMOUNT 1 trial)
- Wilding JPH, et al. Once Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med. 2021;384:989-1002 (STEP 1 trial)
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