Mounjaro vs Wegovy UK: Which is Better for Weight Loss? (2026)
If you’re considering a weight loss injection in the UK, chances are you’ve come across two names: Mounjaro and Wegovy. Both are prescription-only injectable treatments, both are clinically proven, and both are available online through MedExpress. But which one is right for you?
In this guide, we compare Mounjaro vs Wegovy UK across the most important factors — effectiveness, how they work, dosing, side effects and cost — so you can make an informed decision before your online consultation.
What is Mounjaro?
Mounjaro (Tirzepatide) is a once-weekly weight loss injection developed by Eli Lilly. It was MHRA-approved in the UK in 2023 for chronic weight management in adults with a BMI of 30 or above (or 27+ with a weight-related health condition).
Mounjaro works by activating two hormone receptors simultaneously — GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1). This dual-action mechanism is what sets it apart from other weight loss injections currently on the market.
What is Wegovy?
Wegovy (Semaglutide 2.4mg) is a once-weekly weight loss injection developed by Novo Nordisk. Also MHRA-approved in the UK, Wegovy targets GLP-1 receptors only — making it a single-receptor treatment compared to Mounjaro’s dual approach.
Wegovy has been available in the UK slightly longer than Mounjaro and has an extensive body of clinical evidence supporting its use for long-term weight management.
How Do They Compare on Effectiveness?
This is the question most people ask first — and the data is clear.
In clinical trials, Mounjaro (Tirzepatide) achieved an average weight loss of 20–22% of body weight over 72 weeks at the highest dose. Wegovy (Semaglutide) achieved an average of around 15% body weight loss over 68 weeks.
Both results are significantly better than diet and exercise alone, but Mounjaro has consistently shown greater average weight loss in head-to-head comparisons.
That said, individual results vary. Some people respond better to Semaglutide, and your clinical history, lifestyle and starting weight all play a role in the outcome.
How Are They Dosed?
Mounjaro starts at 2.5mg once weekly and increases gradually up to a maximum of 15mg, depending on response and tolerability. The dose escalation takes place over several months to minimise side effects.
Wegovy starts at 0.25mg once weekly and increases over 16 weeks to the maintenance dose of 2.4mg. The escalation schedule is fixed rather than flexible.
Both are self-administered using a pre-filled auto-injector pen, typically into the abdomen, thigh or upper arm.
Side Effects: Mounjaro vs Wegovy
The side effect profiles of both treatments are very similar, as they both act on GLP-1 receptors:
- Nausea
- Vomiting
- Diarrhoea
- Constipation
- Stomach discomfort
- Reduced appetite
Side effects are most common when starting treatment or increasing the dose, and typically improve over time. Because Mounjaro also acts on GIP receptors, some studies suggest it may be slightly better tolerated in terms of gastrointestinal side effects — though this varies between individuals.
Cost Comparison
At MedExpress:
- Mounjaro starts from £129 per month
- Wegovy starts from £99 per month
Wegovy is the more affordable option at the lower doses. However, given Mounjaro’s stronger average weight loss results, many patients find the cost difference worthwhile — particularly over a longer treatment period where greater weight loss may reduce the need for other medications.
Which Should You Choose?
| Mounjaro | Wegovy | |
|---|---|---|
| Active ingredient | Tirzepatide | Semaglutide |
| Receptor targets | GIP + GLP-1 | GLP-1 only |
| Avg. weight loss | 20–22% | ~15% |
| Starting price | £129/month | £99/month |
| Dose frequency | Once weekly | Once weekly |
| MHRA approved | Yes | Yes |
Choose Mounjaro if: You want the maximum possible weight loss results and are comfortable with a slightly higher price point.
Choose Wegovy if: You prefer a lower starting cost, or if Mounjaro is not suitable for your clinical profile.
The best way to determine which treatment is right for you is to complete a free online consultation with the MedExpress clinical team, who can assess your health history and recommend the most appropriate option.
Start Your Weight Loss Journey Today
Both Mounjaro and Wegovy are available at MedExpress with a private prescription following a free online consultation — no GP visit required, with discreet delivery to your door.
👉 Buy Mounjaro UK — from £129 👉 Buy Wegovy UK — from £99