With the sudden rise in the cost of Mounjaro, thousands of people across the UK have been left without access to this life-changing medication, which was helping them lose weight and improve their overall health. As a result, many are now searching for alternatives—and rightly so, many have turned to Wegovy.
Wegovy is a clinically proven weight loss treatment that works in a similar way to Mounjaro, helping patients achieve up to a 14.9% reduction in body weight. However, for those who have been using Mounjaro for an extended period, it’s natural to have some reservations about switching and whether it’s safe to do so.
The good news is that, with the support of our clinical weight loss pharmacists at Longridge Travel Health Clinic, you can safely transition to Wegovy and continue your weight loss journey with confidence. Below, we’ll explore the key differences between Wegovy and Mounjaro, and how our team can guide you through a safe and effective switch.
The difference between Wegovy and Mounjaro
Mounjaro and Wegovy are both weekly injections used to help with weight loss, but they are slightly different in how they work and in the results people usually see.
Wegovy contains a medicine called semaglutide. It works by copying a natural hormone in the body called GLP-1. This hormone helps you feel fuller for longer, slows down the emptying of your stomach, and reduces your appetite. By doing this, it helps people eat less and gradually lose weight.
Mounjaro, on the other hand, contains tirzepatide. It also acts on GLP-1, but it goes a step further by working on another hormone called GIP. This second hormone also plays a role in controlling appetite and metabolism. Because it targets two pathways instead of just one, Mounjaro tends to give stronger results for most people compared with Wegovy.
In terms of effectiveness, both medicines are very good, but clinical trials suggest Wegovy helps people lose around 10 to 15 percent of their body weight over about a year, while Mounjaro can lead to 15 to 20 percent, sometimes more.
Both start at lower doses and are increased gradually to give the body time to adjust. Wegovy is usually cheaper and currently a little easier to get hold of in the UK. Mounjaro, while more effective, tends to be more expensive and can be harder to find. If you use the combined contraceptive pill, there’s another consideration: Mounjaro can reduce its effectiveness during dose changes, so you’d need extra protection for a few weeks each time you increase the dose.
Am I eligible for Wegovy?
Eligibility for Wegovy is set out in the UK under both NICE guidance (for NHS use) and also private prescribing guidelines.
On the NHS, Wegovy is only prescribed for adults who:
- Have a BMI of 35 or higher (that’s classed as obese)
- Have at least one weight-related health problem such as high blood pressure, type 2 diabetes, sleep apnoea, or heart disease
- Are being managed in a specialist weight management service, not just by a GP.
- It can sometimes be considered for people with a BMI of 30–34.9 if they have certain serious health conditions, but this is less common.
For private treatment in the UK, the rules are slightly broader but still safety-focused. Most private clinics, pharmacies, and online prescribers, like those at Longridge Travel Health Clinic will approve Wegovy if:
- You are an adult (18 or over), and
- Your BMI is 30 or above
- Your BMI is 27 or above with at least one weight-related condition (such as high cholesterol, raised blood pressure, type 2 diabetes, or obstructive sleep apnoea).
You’ll also need to complete a consultation form so the prescriber can check for anything that would make it unsafe, for example, a history of pancreatitis, severe digestive problems, pregnancy or breastfeeding, or certain rare thyroid cancers.
What happens if I don’t meet the criteria?
If you don’t quite tick the boxes for Wegovy, it doesn’t automatically mean you’ll get no help. At Longridge Travel Health Clinic, we will usually do two things:
- Look at alternatives – for example, we might recommend a structured diet and lifestyle programme first, or consider a different licensed medicine (like Orlistat) if appropriate.
- Offer a proper assessment – sometimes people think they don’t qualify, but when a prescriber checks BMI correctly and reviews things like blood pressure, cholesterol, or sleep quality, they actually do meet the criteria.
Even if Wegovy isn’t right for you, we can guide you toward the safest and most effective option for your situation.
How to switch from Mounjaro to Wegovy
Switching from Mounjaro (tirzepatide) to Wegovy (semaglutide) can be done safely, but it needs a bit of planning because the two drugs are similar in some ways and quite different in others. The main goal is to avoid doubling up on side-effects, keep your weight management progress going, and make sure the dosing is appropriate for where your body is at.
Safe switching process
- Consultation or review – You’d complete our health questionnaire or speak with our prescriber. We’d look at:
- Your medical history (diabetes, pancreatitis, gallbladder, thyroid, pregnancy/breastfeeding, etc.)
- Current medication list (to check for interactions).
- Which dose of Mounjaro you were on, and how long you’ve been using it.
- Your weight/BMI and any weight-related conditions.
- This step confirms you’re eligible for Wegovy which we will prescribe for you and ensures it’s safe to switch.
- Don’t overlap them – You shouldn’t take Mounjaro and Wegovy in the same week. They both slow stomach emptying and act on GLP-1, so doubling up would make nausea, vomiting, or constipation much more likely.
- Leave a gap of about one week– The safest approach is to stop your usual Mounjaro dose, wait until your next injection day comes around, and then start Wegovy instead. That way the old dose has cleared enough to avoid stacking the medicines.
- Start Wegovy at the beginning dose, not the maximum – Even if you were on a high dose of Mounjaro, we generally recommend starting Wegovy at 0.25 mg once weekly and titrating up every 4 weeks. This is because your body needs to adjust to semaglutide specifically. Jumping straight to a high Wegovy dose risks severe side effects. However, this does differ from person to person, so we will always create a treatment plan that works best for you.
Keep up lifestyle support and expect some difference in effect
Your body doesn’t “forget” the weight you’ve already lost just because the medicine changes. Fat that’s been burned off doesn’t suddenly come back — what matters is how you manage the transition. The appetite-control effect may feel weaker at the very beginning of Wegovy, but the habits you built on Mounjaro — eating smaller portions, recognising fullness earlier, moving more — are still yours. That’s why most people don’t go back to square one.
It’s also true that you might see some short-term fluctuations — maybe the scales stall or even creep up by a kilo or two during the switch. That’s not failure, it’s just your body adjusting. As the Wegovy dose increases, appetite control usually strengthens again and weight loss resumes.
The point about habit formation is key. Studies suggest it takes about 2 months of consistent behaviour to really set a habit. If you’ve been on Mounjaro longer than that, chances are your new eating and lifestyle patterns are already ingrained. Wegovy then acts as a “support system” to help you maintain and deepen those routines, not as the sole driver of your progress.
Do I need to start on the lowest dose of Wegovy if I switch?
In most cases, you do need to start Wegovy at the lowest dose (0.25 mg weekly), even if you’ve already been on a higher dose of Mounjaro.
Here’s why:
- Different medicine, different potency. Even though both Mounjaro and Wegovy act on the GLP-1 pathway, semaglutide (Wegovy) isn’t equivalent to tirzepatide (Mounjaro). Your body has to “learn” this drug’s side-effect profile.
- Side-effects build with dose. If you were to jump straight to a higher dose of Wegovy, the chance of nausea, vomiting, reflux, or severe bloating would be much higher. Starting low keeps this tolerable.
- Titration protects long-term use. The slow step-up isn’t just about comfort — it’s about being able to stay on treatment. People who try to rush doses are more likely to stop altogether because the side-effects become unmanageable.
- No official conversion table exists. Unlike, say, switching between two blood pressure tablets, there isn’t a clinically accepted “equivalent dose” of tirzepatide to semaglutide. That’s why prescribers err on the side of caution and restart at 0.25 mg.
However, below you can find what a typical dosing schedule looks like when switching from Mounjaro to Wegovy for each dose:
Are there any differences when changing treatments?
The injection technique and storage are broadly similar between Mounjaro and Wegovy, but there are a few subtle differences worth knowing if you’re switching.
- Wegovy: can be kept at room temperature (below 30 °C) for up to 6 weeks.
- Mounjaro: can be kept at room temperature (below 30 °C) for up to 21 days.
Both pens are single-use and already pre-filled to deliver one full dose. You place it against your skin, unlock, press the button, and it automatically inserts and injects. You dispose of the pen after each injection.
Some people find the Wegovy needle insertion slightly more noticeable than Mounjaro’s, but both are designed to be very simple. Both can be injected into the abdomen, thigh, or upper arm. Rotating sites each week reduces irritation.
Why should I consider switching?
Mounjaro (tirzepatide) and Wegovy (semaglutide) are both excellent treatments, but there are some reasons why you might choose to switch.
- Cost – Mounjaro is usually more expensive than Wegovy when bought privately in the UK. If you’re paying out of pocket and finding the cost difficult to sustain long term, Wegovy can be a more affordable alternative while still being highly effective.
- Availability – Supply of Mounjaro has been patchy in the UK. Some pharmacies struggle to keep certain doses in stock. Wegovy, while not immune to shortages, is often easier to get hold of. If you want consistent treatment without breaks, switching can be practical.
- Side-effects and tolerability – Both medicines cause digestive side-effects, but not always in the same way. Some people find Mounjaro gives more constipation or bloating, while Wegovy causes more nausea early on. If one drug’s side-effects are making it hard to continue, switching is reasonable.
- Contraceptive considerations – Mounjaro can reduce the effectiveness of oral contraceptive pills during dose increases, meaning you need to use a barrier method for 4 weeks after each escalation. Wegovy doesn’t have this issue, which can make it simpler for women who rely on the pill.
Will I experience side effects when switching from Mounjaro to Wegovy?
There’s a chance you’ll experience side effects when switching from Mounjaro to Wegovy, but the type and intensity can vary depending on your body, your dose history, and how carefully the switch is managed.
Even if you tolerated Mounjaro well, starting Wegovy means introducing a different drug (semaglutide). The body doesn’t automatically “carry over” tolerance, which is why prescribers start you back at the lowest dose of Wegovy (0.25 mg). This helps to reduce the risk of overwhelming nausea or stomach upset.
The most common side effects after switching:
- Nausea and queasiness, especially in the first 2–4 weeks.
- Bloating, indigestion, or reflux, since Wegovy can slow stomach emptying.
- Diarrhoea or constipation (some people notice a shift in bowel habits when changing medication).
- Fatigue or headache, usually mild and temporary.
These are very similar to Mounjaro’s side effects, though the balance can feel different: Wegovy is often described as being more nauseating at first, whereas Mounjaro tends to cause more constipation.
Most side effects are temporary and settle as your body adjusts. The gradual titration (increasing every 4 weeks) is designed to give your system time to adapt. Some people find that because they’ve already been on a GLP-1 medicine (Mounjaro), the transition is easier — but that’s not guaranteed.
How to make it smoother
- Eat smaller meals, chew slowly, and stop when comfortably full.
- Avoid greasy, spicy, or very rich foods during the first few weeks.
- Stay hydrated — little and often.
- Use anti-sickness remedies (like ginger or, if needed, a prescribed anti-nausea tablet) if symptoms are hard to manage.
- Stick to your dose schedule — don’t increase early, even if you tolerated Mounjaro well.
Your Weight Loss Journey with Longridge Travel Health Clinic
At Longridge Travel Health Clinic, we understand that switching medications can feel like a big step, but you don’t have to do it alone. Our experienced clinical weight loss team is here to guide you through every stage of your transition from Mounjaro to Wegovy, ensuring it’s done safely, smoothly, and with your long-term goals in mind.
We offer personalised consultations, ongoing support, and medication reminders to help keep your treatment on track. Beyond prescriptions, we provide expert advice on nutrition, exercise, and sustainable habit changes because we know that real, lasting weight loss is about more than just medication.
If you’re considering switching to Wegovy or exploring your next step, our team is here to help you make confident, informed decisions. Book a consultation today and take the next step in your weight loss journey with a team that truly cares.