Switching from Mounjaro to Wegovy

Switching from Mounjaro to Wegovy is possible, but it is a prescriber decision, not a simple swap. Mounjaro (tirzepatide) and Wegovy (semaglutide) work in related but different ways, use different dose strengths, and there is no official dose conversion between them. People most often consider the change because of cost, side effects, supply or a wish to access Wegovy's heart-protection licence. On average, Wegovy produced less weight loss than Mounjaro in a head-to-head trial, so expectations matter. This guide explains the reasons, the evidence and what a safe, supervised switch usually involves.

Why people consider switching from Mounjaro to Wegovy

Most people who start Mounjaro stay on it if it is working and well tolerated. A switch is usually prompted by a specific problem or a change in circumstances. Understanding your own reason helps you and your prescriber judge whether moving to Wegovy is likely to solve it.

Cost and affordability

Cost is one of the most common reasons in private care. In September 2025 the UK list price of Mounjaro rose substantially, and many private providers passed this on. Some people found the higher monthly cost hard to sustain and asked whether semaglutide might be more affordable for them. Whether that turns out to be true depends on the provider, the dose you need and how prices have moved since. We do not quote prices in our guides because they change frequently; you can see how the medicines and services compare on our prices page, and read more about what happened in our guide to the Mounjaro price rise.

It is worth being realistic here. If cost is the only reason for switching and Mounjaro is working well, your prescriber may talk you through the trade-off: a medicine that is cheaper for you but, on average, somewhat less effective. For some people that trade-off is reasonable; for others it is not. Our guide to the long-term cost of GLP-1 treatment may help you think it through.

Side effects and tolerability

Both medicines commonly cause gastrointestinal side effects such as nausea, diarrhoea, constipation, indigestion and reduced appetite. Some people tolerate one better than the other, although there is no reliable way to predict this in advance. If you have had persistent side effects on Mounjaro despite dose adjustments, your prescriber may consider whether a different medicine is worth trying. Equally, they might suggest staying on Mounjaro at a lower dose first.

Supply and availability

From time to time, particular strengths of weight-loss medicines have been in short supply in the UK. If a specific Mounjaro dose is unavailable, a prescriber may consider alternatives, which could include Wegovy. Supply situations change, so check with your provider rather than relying on news reports.

Cardiovascular considerations

Wegovy has a licence in the UK that extends to reducing the risk of major cardiovascular events in some adults with established cardiovascular disease and overweight or obesity. This is based on the SELECT trial, which found that semaglutide 2.4 mg reduced the risk of heart attack, stroke or cardiovascular death by about 20% compared with placebo over an average follow-up of more than three years. If you have heart disease, your prescriber or cardiologist may see this evidence as a reason to favour Wegovy. Read more in our guide to Wegovy and the SELECT trial.

Tirzepatide's own cardiovascular outcome trials have been under way, and results may change this picture over time. At the time of writing, check the current SmPC for each medicine's licensed indications.

NHS access

Some people start on a private prescription and later become eligible for NHS treatment. NHS access to Wegovy follows NICE TA875 and is generally through specialist weight management services, while NHS tirzepatide follows NICE TA1026 and has been rolled out in phases, including in primary care from June 2025. Which medicine you are offered on the NHS depends on local services, your eligibility and clinical factors, and it may not be the one you were taking privately.

How Mounjaro and Wegovy differ

It helps to understand what changes when you switch, because it explains why there is no simple conversion.

Because the two medicines act on different receptors and are measured in different milligram amounts, a milligram of one does not correspond to a milligram of the other. That is why your prescriber, not a chart, should decide your starting dose.

What about Wegovy 7.2 mg?

In January 2026 the MHRA approved a maximum weekly semaglutide dose of up to 7.2 mg for weight management in adults with obesity (a BMI of 30 or more). It is given as three 2.4 mg injections and does not apply to people with a BMI under 30 or to those using Wegovy for cardiovascular risk reduction. The approval was based on the STEP UP trial, which reported greater weight loss with 7.2 mg than with 2.4 mg. Availability through private providers and the NHS can vary, so check the current SmPC and ask your prescriber whether it is relevant to you.

What the evidence says about results after switching

The most important evidence for anyone considering this switch is the SURMOUNT-5 trial, published in the New England Journal of Medicine in 2025. It directly compared tirzepatide (up to 15 mg or the maximum tolerated dose) with semaglutide (up to 2.4 mg or the maximum tolerated dose) in adults with obesity but without type 2 diabetes.

In other words, people on tirzepatide lost more weight on average. That does not mean everyone did better on tirzepatide; individual responses overlapped widely, and some people lose more on semaglutide than others do on tirzepatide. But the average difference is meaningful when you think about a switch.

Importantly, SURMOUNT-5 compared people who started on each medicine. It did not study people switching from one to the other, and there is limited trial evidence on outcomes after switching from tirzepatide to semaglutide specifically. What we can reasonably say is:

• Some people may see slower progress or some regain, particularly if they were responding very well to Mounjaro.
• Some people maintain their weight well, especially if they were already near a stable weight and the switch is smooth.
• Gaps matter. Trials of stopping treatment, such as STEP 4 (semaglutide) and SURMOUNT-4 (tirzepatide), show that appetite and weight tend to return when medicine is withdrawn. A long gap between medicines may allow some of this to happen.
• Starting dose matters. If you restart at a low Wegovy dose to reduce side effects, its effect on appetite may initially be weaker than what you were used to.

For a deeper look at the trial itself, see our guide to SURMOUNT-5 and our broader Mounjaro vs Wegovy comparison.

How prescribers usually approach the switch

Every prescriber will tailor a switch to the individual. What follows is a general description of the factors they consider, not instructions to follow on your own. Please do not change medicine or dose without speaking to your prescriber.

1. A review of your current treatment

Your prescriber will usually ask:

• Which Mounjaro dose you are on and how long you have been on it
• How much weight you have lost and whether it is still changing
• What side effects you have had and how severe they were
• When you took your last injection
• Whether you have had any gaps in treatment
• Any changes in your health, other medicines or plans for pregnancy

They will also re-check that Wegovy is suitable for you, because the two medicines share many, but not all, cautions. For example, both are unsuitable in pregnancy and need care in people with a history of pancreatitis or certain gallbladder problems. Our guide on who should not take GLP-1 medicines covers this in more detail.

2. Choosing a starting dose

There is no official conversion. The Wegovy SmPC describes a standard dose-escalation schedule starting at 0.25 mg weekly, with dose increases every four weeks to reduce gastrointestinal side effects. When someone has already been taking a related medicine, some prescribers use clinical judgement to decide whether a full restart from the lowest dose is needed, and this varies between clinicians and services.

The prescriber is balancing two risks:

• Starting too low may mean weaker appetite control for a while, with a risk of some regain.
• Starting too high may cause more nausea, vomiting or diarrhoea, which can, in turn, lead to dehydration.

This is exactly why the decision belongs with a prescriber who knows your history. You can read the standard escalation steps in our Wegovy dosing schedule guide, but these are for understanding, not for self-adjusting.

3. Timing the first Wegovy dose

Both medicines are taken once a week. Prescribers often plan the first dose of the new medicine around when the next dose of the old one would have been due, so there is no long gap and no overlap. However, timing may be different if you have already paused Mounjaro, had a missed dose or had significant side effects. Follow your prescriber's specific instructions.

4. Planning dose increases

After starting Wegovy, your prescriber will typically review you before each dose increase. They will check side effects, your weight and how you are coping with eating. Not everyone needs to reach the highest dose; the aim is the dose that works and is tolerated.

5. Ongoing monitoring

Expect check-ins at least as often as you had on Mounjaro. Good services will ask about your weight, side effects, mood, any new symptoms and how you are getting on with eating and activity. If you are not losing weight or are regaining after the switch, say so; your prescriber can review the plan.

What to expect in the first weeks

Experiences differ, but these are common themes that people are told to look out for.

Appetite changes

Some people notice their appetite returns a little during the changeover, especially if they started Wegovy at a low dose. This is not a sign that you have "failed". It is a predictable effect of the medicine changing, and it often settles as the dose is adjusted. Planning regular, protein-rich meals can help; see our guide on what to eat on GLP-1 medication.

Side effects

Gastrointestinal side effects may reappear, particularly in the first days after each injection and after each dose increase. Practical measures that NHS and SmPC guidance commonly mention include eating smaller meals, stopping when you feel full, avoiding very fatty or rich foods, and drinking enough fluids. If side effects are severe or don't settle, contact your prescriber.

Weight changes

It is common to see a period of slower change. Some people see a small increase in weight for a few weeks before things stabilise. Look at the trend over a month or two rather than week by week. Our guide on measuring progress beyond the scales suggests other ways to track how you are doing.

Different pen, different technique

Wegovy uses a FlexTouch pen, which works differently from the Mounjaro KwikPen. Your provider should show you how to use it, and the patient information leaflet has step-by-step instructions. Our guide to the Wegovy pen explains the basics.

Practical considerations

Switching provider at the same time

Some people switch medicine and provider together, often because of cost. This adds another layer, as your new provider needs evidence of your previous treatment to prescribe safely. They will usually ask for details of your previous prescriptions and recent weight. If you are moving provider, read our guide on switching providers mid-treatment, and compare regulated services on our providers page.

Leftover Mounjaro

Do not keep using leftover Mounjaro alongside Wegovy. Ask your pharmacy how to dispose of unused medicine and pens safely; most community pharmacies accept returned medicines.

Keeping your GP informed

Even if your treatment is private, it is wise to let your GP know which medicine you are taking. This matters for other prescribing decisions, for any procedures that need sedation or anaesthesia, and for your medical record. Reputable online providers usually ask for your consent to share details with your GP.

Contraception

Tirzepatide can reduce the effectiveness of oral contraceptives, particularly around the start of treatment and after dose increases, and the Mounjaro SmPC advises additional precautions during these periods. Semaglutide does not carry the same specific advice, but vomiting or diarrhoea from any cause can affect how well the pill is absorbed. Discuss contraception with your prescriber when switching. Our guide on GLP-1 medicines and contraception has more detail.

Is switching the right move for you?

There is no universally correct answer. These questions may help you prepare for a conversation with your prescriber:

Alternatives your prescriber may discuss include staying on Mounjaro at a different dose, a tablet option (see our guide to switching from an injection to a GLP-1 tablet), or, in some cases, a supervised pause with a plan for diet, activity and follow-up.

If you are thinking of going the other way, our guide to switching from Wegovy to Mounjaro covers that scenario. More on Wegovy as a medicine is in our Wegovy hub.

Common misconceptions about switching

A few misunderstandings come up often when people research this change online. Clearing them up can make your conversation with a prescriber more productive.

"Higher milligrams means a stronger medicine"

Mounjaro doses (2.5 mg to 15 mg) look much larger than Wegovy doses (0.25 mg to 2.4 mg), but the numbers simply reflect how much of each molecule is needed to act on its receptors. A 2.4 mg dose of semaglutide is not "weaker" than a 2.5 mg dose of tirzepatide because of its milligram value, and neither number tells you how the two compare. This is one more reason not to rely on informal conversion charts.

"If I lost weight on Mounjaro, I'll lose the same on Wegovy"

Your previous response is useful information, but it can't tell you for certain what will happen next. The two medicines work differently, and SURMOUNT-5 showed a meaningful average difference in weight loss. Some people respond similarly to both; others notice a difference in appetite control.

"A short break between medicines resets my body"

There is no evidence that pausing treatment before switching brings any benefit. In fact, trials of stopping treatment, such as STEP 4 and SURMOUNT-4, show that appetite and weight tend to return without medicine. Unless your prescriber advises a pause for a specific clinical reason, a well-timed switch with no long gap is generally the aim.

"Switching means starting from scratch"

Not necessarily. While some prescribers restart Wegovy from the lowest dose, others may use clinical judgement based on your history. Either way, the weight you have already lost doesn't disappear because you change medicine, and many people maintain their progress.

Questions to ask your prescriber

Going into the consultation with a few questions written down can help you understand the plan:

• Why do you think switching is, or isn't, a good idea for me?
• What starting dose of Wegovy are you suggesting, and why?
• When should I take my first Wegovy dose in relation to my last Mounjaro injection?
• How quickly might my dose be increased, and what will you check before each increase?
• What should I do if side effects are worse than expected?
• How will we judge whether Wegovy is working for me?
• If it doesn't suit me, what would the options be?

A good prescriber will welcome these questions and explain their reasoning clearly.

For related guides, see our switching topic hub.

When to speak to a professional

Talk to your prescriber before making any change to your medicine or dose, and contact them promptly if:

• You are considering stopping Mounjaro or starting Wegovy
• You have missed doses or had a gap of more than a week or two
• Side effects are making it hard to eat or drink
• You are not losing weight, or are regaining, after the switch
• You become pregnant, are planning pregnancy or are breastfeeding
• You start any new medicine, especially for diabetes

Seek urgent medical help (NHS 111, or 999 in an emergency) if you have:

• Severe, persistent abdominal pain, which may spread to your back, with or without vomiting (a possible sign of pancreatitis)
• Pain in the upper right side of your abdomen, fever, or yellowing of the skin or eyes (possible gallbladder problems)
• Repeated vomiting or diarrhoea with signs of dehydration, such as dizziness, very dark urine or passing little urine
• Signs of a severe allergic reaction, such as swelling of the face, lips or throat, or difficulty breathing
• Symptoms of low blood sugar if you also take insulin or a sulfonylurea

You can report suspected side effects through the MHRA Yellow Card scheme.