Thinking of switching from Wegovy to Mounjaro, or Mounjaro to Wegovy? Learn when to switch, how doses are chosen, how long to wait and what side effects to expect.
Can you switch between Wegovy and Mounjaro?
Yes. It is possible to switch from Wegovy to Mounjaro, or from Mounjaro to Wegovy, under the guidance of a prescriber.
People switch for many reasons, including side effects, a weight loss plateau, cost and availability.
The most important things to know are:
- There is no official dose conversion between the two medicines
- You will usually start the new medicine one week after your last dose of the old one
- You will often start on a lower dose of the new medicine and build up again
- Never take both medicines at the same time
- The switch should always be planned with your prescriber
This guide explains why people switch, how a switch usually works in each direction, what to expect, and how to make the change as smooth as possible.
How are Wegovy and Mounjaro different?
Both are weekly injections used for weight management, but they contain different medicines.
Wegovy contains semaglutide, which acts on GLP-1 receptors.
Mounjaro contains tirzepatide, which acts on both GLP-1 and GIP receptors.
Because they work in slightly different ways, your body may respond differently to each one, both in terms of weight loss and side effects.
Their doses are also measured on completely different scales:
- Wegovy: 0.25 mg, 0.5 mg, 1 mg, 1.7 mg, 2.4 mg
- Mounjaro: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, 15 mg
The milligram numbers cannot be compared directly. You can read a full comparison in our article: Is Mounjaro better than Wegovy?
Why do people switch?
Side effects
Some people tolerate one medicine better than the other. If nausea, constipation or another side effect is persistent on one, a prescriber may suggest trying the alternative.
A weight loss plateau
If weight loss has stalled at the highest tolerated dose, switching may be considered.
In the SURMOUNT-5 trial, which compared the two medicines directly, tirzepatide produced greater average weight loss than semaglutide over 72 weeks. For this reason, some people who plateau on Wegovy move to Mounjaro.
Before switching for this reason, it is worth checking whether something else is holding you back. See why you may not be losing weight on Mounjaro or Wegovy.
Cost
Private prices differ between the two medicines and between dose strengths, and prices have changed over time. After the UK list price of Mounjaro rose in September 2025, many people looked at whether Wegovy would be more affordable for them.
Our Mounjaro cost guide explains current pricing.
Availability
Occasional supply problems with a particular medicine or strength can prompt a switch.
Other health factors
Wegovy has evidence showing a reduction in the risk of heart attack and stroke in people with established cardiovascular disease and overweight or obesity. For some people, this may influence the choice.
Preference for a tablet
Some people prefer to move from an injection to an oral option. See Wegovy tablets vs Mounjaro and our guide to Foundayo in the UK.
Is there a dose conversion chart?
No. There is no official, licensed dose conversion between Wegovy and Mounjaro.
You may see conversion charts online. These are based on opinion and local practice, not on the product licences.
The two medicines were not studied as direct swaps, and people respond differently to each.
For this reason, the starting dose of your new medicine is a clinical decision made by your prescriber, based on:
- The medicine and dose you are currently taking
- How long you have been on it
- How well you have tolerated it
- When you took your last dose
- Your weight loss so far
- Your medical history
Switching from Wegovy to Mounjaro
When do you start?
In most cases, you take your first Mounjaro dose one week after your last Wegovy dose, on the day your next Wegovy injection would have been due.
There is usually no need for a long gap.
What dose will you start on?
Mounjaro's licence states that treatment starts at 2.5 mg.
Many prescribers will start people switching from Wegovy on 2.5 mg, particularly those coming from lower Wegovy doses or those who have had side effects.
Some prescribers may consider starting at 5 mg for people who have been stable on a higher dose of Wegovy and have tolerated it well.
You will not normally be started on a high dose of Mounjaro, even if you were on the maximum dose of Wegovy.
What happens next?
Your dose is then increased gradually in 2.5 mg steps, at least four weeks apart, according to your response. Our Mounjaro dosage guide explains each step.
Important note for women taking the pill
Mounjaro may reduce the effectiveness of the oral contraceptive pill. If you take the pill, you are advised to use a non-oral or barrier method of contraception for four weeks after starting Mounjaro and for four weeks after each dose increase.
This applies when you switch to Mounjaro, even if you have been taking Wegovy for some time. Read more in our guide to weight loss injections, contraception and pregnancy.
Switching from Mounjaro to Wegovy
When do you start?
As with the reverse switch, you usually take your first Wegovy dose one week after your last Mounjaro dose.
What dose will you start on?
Wegovy's licence states that treatment starts at 0.25 mg.
In practice, prescribers often take your Mounjaro dose and tolerance into account. People coming from lower doses of Mounjaro are commonly started at a low Wegovy dose, while those who have been stable on higher doses of Mounjaro may be started at an intermediate dose.
Your prescriber will explain which dose they recommend and why.
What happens next?
Your dose is increased every four weeks, if appropriate, towards the 2.4 mg maintenance dose. See our Wegovy dosage guide.
Do you need a washout period?
A "washout" means leaving a gap so that the first medicine clears from your body before starting the second.
For most people switching between Wegovy and Mounjaro, a long washout is not necessary. The usual approach is simply to start the new medicine when your next weekly dose would have been due.
Both medicines stay in the body for some time after the last injection. This is one reason your prescriber may start you on a lower dose of the new medicine, as there will be some overlap in effect.
If you have had significant side effects on your current medicine, your prescriber may suggest waiting a little longer for these to settle before starting the new one.
Never inject both medicines in the same week unless you have been specifically told to do so.
What side effects should you expect when switching?
Switching is, in effect, starting a new medicine.
You may experience some of the side effects you had when you first started treatment, such as:
- Nausea
- Diarrhoea or constipation
- Indigestion, reflux or burping
- Reduced appetite
- Tiredness
For most people, these are mild and short-lived.
To reduce the chance of problems:
- Eat smaller meals and eat slowly for the first few weeks
- Avoid greasy, fried and very rich foods
- Stay well hydrated
- Limit alcohol
- Avoid switching just before a holiday or major event
Our guide to weight loss injection side effects explains what is normal and when to seek help.
Seek urgent medical attention for severe, persistent abdominal pain, with or without vomiting.
Will you gain weight when you switch?
Some people worry that weight will return during a switch, especially if they restart on a low dose.
A brief change in appetite is possible. Some people notice they feel a little hungrier for the first few weeks while they build up to an effective dose of the new medicine.
For most people, any change is small and temporary.
You can help protect your progress by:
- Keeping to your usual meal structure
- Prioritising protein and fibre
- Staying active, including strength training
- Weighing weekly, not daily, and not over-reacting to small fluctuations
See our guide on what to eat on Mounjaro or Wegovy for practical ideas.
Will the new medicine work better?
Not necessarily, and it is sensible to keep expectations realistic.
On average, Mounjaro produced more weight loss than Wegovy in a direct comparison trial. But individuals vary, and some people do better on Wegovy.
If you are switching because of a plateau, remember that weight loss naturally slows over time on any treatment. A plateau does not always mean the medicine has stopped working. It may mean your body has reached a new balance.
Our article on how much weight you can lose on Mounjaro or Wegovy explains the typical pattern.
The pens are different too
If you switch medicine, you also switch device.
- Mounjaro KwikPen: primed before every injection; hold and count slowly to five; needles supplied separately.
- Wegovy FlexTouch: flow checked only when the pen is new; count slowly to six after the counter reaches zero; needles included.
Storage rules also differ slightly. After first use, a Mounjaro pen should be used within 30 days, while a Wegovy pen can be used for up to six weeks.
Read the new Instructions for Use carefully, and see our guides on how to inject Mounjaro or Wegovy and how to store Mounjaro and Wegovy.
What about switching from other medicines?
From Ozempic
Ozempic contains semaglutide, the same active ingredient as Wegovy, but it is licensed in the UK for type 2 diabetes. If you have diabetes and take Ozempic, any change should be managed by the team looking after your diabetes. Read more in Ozempic vs Wegovy.
From Saxenda
Saxenda (liraglutide) is a daily injection. People moving from Saxenda to a weekly injection will usually start at the standard starting dose of the new medicine.
From another provider
If you are moving to a new pharmacy as well as a new medicine, you will usually be asked for evidence of your previous treatment, such as your starting weight, your current dose and the date of your last injection.
What your prescriber needs to know
To plan a safe switch, be ready to share:
- Which medicine and dose you are currently taking
- How long you have been on that dose
- The date of your last injection
- Any side effects you have had
- Your starting weight and current weight
- Any missed doses in recent weeks
- Other medicines, including the contraceptive pill, insulin and diabetes tablets
- Your reasons for wanting to switch
What not to do when switching
- Do not take both medicines together
- Do not choose your own starting dose from an online chart
- Do not start at a high dose to "match" your old one
- Do not use leftover pens from a friend or family member
- Do not buy from unregulated sellers because they are cheaper or ask fewer questions
If you are unsure how to tell a legitimate supplier from an unsafe one, read our guide to fake weight loss injections.
Switching with SynovaMed
SynovaMed supplies both Mounjaro and Wegovy, so if you want to change treatment, our clinical team can review your history and advise on a suitable plan.
If you are already a patient, mention that you would like to switch in your next check-in or contact our team. If you are new to us, you can start through our weight loss programme.
Frequently Asked Questions
Can I switch from Wegovy to Mounjaro?
Yes, with a prescriber's guidance. You will usually take your first Mounjaro dose one week after your last Wegovy dose, starting at a low dose.
Can I switch from Mounjaro to Wegovy?
Yes. You will usually take your first Wegovy dose one week after your last Mounjaro dose, at a dose chosen by your prescriber.
What dose of Mounjaro is equivalent to Wegovy 2.4 mg?
There is no official equivalent. The two medicines are different and their doses cannot be converted directly.
How long should I wait between Wegovy and Mounjaro?
Usually one week, so that the new medicine starts when your next dose would have been due.
Do I have to start again at the lowest dose?
Often, yes, or at a low dose. Your prescriber will decide based on your current dose and how well you have tolerated treatment.
Will I get side effects again when I switch?
You might, as your body adjusts to a new medicine. They are usually mild and temporary.
Will I regain weight if I switch from Mounjaro to Wegovy?
Most people do not regain significant weight, although appetite may increase slightly while the new dose is being built up.
Is it worth switching to Mounjaro if Wegovy has stopped working?
It may be, but first check for other causes of a plateau. Your prescriber can advise whether a switch is likely to help.
Can I use both Wegovy and Mounjaro together?
No. They should not be used at the same time.
Do I need extra contraception when switching to Mounjaro?
If you take the oral contraceptive pill, yes. Use a non-oral or barrier method for four weeks after starting Mounjaro and after each dose increase.
The bottom line: switching between Wegovy and Mounjaro
Switching between Wegovy and Mounjaro is common and can be done safely with the right plan.
There is no official dose conversion.
Start the new medicine one week after your last dose of the old one.
Expect to start low and build up again.
Never use both together.
Be prepared for mild, temporary side effects.
Let your prescriber decide the dose, not an online chart.
Whichever direction you are switching, the goal is the same: a treatment that works for you, that you can tolerate, and that you can continue for as long as you need it.
Medical Disclaimer
This article is intended for general educational purposes and does not replace personalised medical advice, diagnosis or treatment. There is no licensed dose conversion between Wegovy and Mounjaro, and any switch should be planned and supervised by a qualified prescriber. Mounjaro, Wegovy and other prescription weight-management medicines are not suitable for everyone. If you experience severe abdominal pain, persistent vomiting or other concerning symptoms, seek medical attention promptly.