Switching from Mounjaro to Wegovy: What You Need to Know
A detailed guide to understanding GLP-1 medicines, the reasons behind Mounjaro’s price adjustment, the benefits of Wegovy, and what a safe and supported transition entails.
Understanding GLP-1 Medicines
GLP-1 receptor agonists (GLP-1s) are a class of medicines that function by mimicking a natural hormone released after eating, which helps people feel fuller. This action contributes to reduced hunger and an improved ability to eat less, supporting long-term weight loss.
Mounjaro (tirzepatide) is a dual receptor agonist, acting on both GLP-1 and GIP hormones involved in appetite and blood sugar control. Wegovy (semaglutide), on the other hand, works specifically on the GLP-1 receptor.
In the UK, GLP-1 medicines are licensed to treat specific medical disorders and should only be used if you are overweight, obese, or diabetic. They are carefully assessed by the UK medicines regulator (MHRA) for safety and effectiveness.
Why the Price of Mounjaro is Increasing
The manufacturer of Mounjaro, Eli Lilly, has announced a significant price increase for the UK market. From 1st September 2025, the monthly cost will rise to between £160–£320 per pen, depending on the dose. This adjustment is intended to align UK pricing with international standards, as it was initially priced lower to ensure patient access.
What is Wegovy?
Wegovy is a once-weekly weight loss injection developed by Novo Nordisk and licensed in the UK. Its active ingredient, semaglutide, is a GLP-1 receptor agonist. It works by mimicking the body’s natural hormones to help you feel fuller for longer, reduce hunger, and improve your ability to eat less, ultimately supporting long-term weight loss.
It is licensed for weight management in people with obesity, or those who are overweight with related health problems, alongside a reduced-calorie diet and exercise.
Benefits of Switching to Wegovy
Wegovy is considered a strong alternative to Mounjaro with comparable outcomes. Key benefits include:
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Proven Weight Loss: Clinical trials show patients can lose up to 15-21% of their body weight, with over 50% of participants losing 15% or more of their baseline weight.
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Strong STEP-UP Study Results: An upcoming higher dose of Wegovy has shown even more promising results, with participants achieving up to 20.7% weight loss.
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Fat Loss Over Muscle Loss: Studies confirm Wegovy primarily promotes the loss of unhealthy visceral fat while helping to preserve lean muscle mass.
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Improved Waist Circumference: Patients have observed waist reductions of up to 5.3 inches, contributing to better cardiovascular health.
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Heart Protection: Uniquely, Wegovy is licensed to reduce the risk of cardiovascular events (like heart attacks and strokes) by up to 20% in people with heart disease.
The Switching Process
Switching medications can seem daunting, but a clinical team can provide support for a safe transition.
Personalised Review
A clinical team will review your Mounjaro history, side effects, weight loss progress, and treatment goals to plan a safe switch.
Starting Dose for Wegovy
You may be able to start on a higher dose of Wegovy depending on how well you tolerated Mounjaro. If you experienced side effects, a lower starting dose might be chosen.
"Washout" Period
A long washout period is not typically required. A 7-day gap between your last Mounjaro dose and first Wegovy injection is usually sufficient to minimise overlapping side effects.
Tailored Prescription
Your ideal Wegovy dose will be determined by your prescriber to ensure continued progress without necessarily restarting from the lowest dose, unless clinically necessary.
Key Considerations for GLP-1 Medicines
When considering any GLP-1 medicine, including Wegovy, it's vital to be aware of several important factors:
Prescription Only
All GLP-1 medicines are prescription-only and must be prescribed by a healthcare professional. They should never be bought from unregulated sellers to avoid significant health risks from fake products.
BMI Requirements
Wegovy is licensed for individuals with a BMI of 30 or above, or a BMI of 27 or above with at least one weight-related condition. You may still be able to continue treatment if your BMI drops below 30.
Contraception and Pregnancy
GLP-1 medicines should not be taken during pregnancy or just before trying to conceive. A "wash-out" period of at least 2 months for Wegovy and 1 month for Mounjaro is recommended before trying to get pregnant.
Note on Oral Contraceptives:
If using Mounjaro with an oral contraceptive, a non-oral, barrier form of contraception (e.g., condom) is advised for four weeks after starting and after any dose increase.
Surgery or Operation
Always inform your healthcare team, including the anaesthetist, if you are taking a GLP-1 medicine prior to a surgical procedure, as these medicines slow stomach emptying.
Conclusion
The impending price increase for Mounjaro makes Wegovy an increasingly attractive alternative for many. Both are effective GLP-1 treatments, but Wegovy offers strong clinical trial results, specific cardiovascular benefits, and a comparable weight loss profile. Making the switch, when guided by a healthcare professional, can be a safe and effective way to continue your weight management or diabetes treatment journey. Always ensure you obtain medicines from legitimate sources and report any adverse reactions to the Yellow Card scheme.
References
- Wegovy® STEP trial data — Novo Nordisk
- UK MHRA guidance on GLP-1 prescribing
- STEP-UP press release, 2025 – Novo Nordisk