Two injectable weight loss medications have dominated conversations in UK healthcare over the past few years, and for good reason. Both Wegovy and Mounjaro have delivered weight loss results that were previously associated only with bariatric surgery. But they are not identical treatments. They work through different mechanisms, produce different average results, carry different cost considerations, and suit different patient profiles.
At Cleckheaton Pharmacy, we provide professionally supervised weight loss injection programmes and are often asked which of these two medications is the better option. The honest answer is that it depends entirely on the individual. This guide lays out everything you need to know to understand the differences, the evidence, and what to consider when making a decision alongside a qualified clinician.
What Are Wegovy and Mounjaro?
Wegovy is the brand name for semaglutide 2.4mg, a once-weekly injectable medication developed by Novo Nordisk. It is approved in the UK for chronic weight management in adults with obesity or overweight alongside at least one weight-related health condition.
Mounjaro is the brand name for tirzepatide, a once-weekly injectable medication developed by Eli Lilly. Like Wegovy, it is approved in the UK for both type 2 diabetes and chronic weight management. Mounjaro is a newer medication and has attracted significant attention because of the scale of its clinical trial results.
Both medications are prescription-only, must be administered as subcutaneous injections once per week, and require supervised prescribing from a qualified clinician. Neither is available over the counter, and neither should be obtained from any source that does not require a full medical consultation.
How Mounjaro Works vs How Wegovy Works: The Key Difference
The primary difference between Wegovy and Mounjaro lies in their mechanism of action.
Wegovy: GLP-1 Receptor Agonist
Wegovy works by mimicking the GLP-1 hormone, which:
- Signals fullness to the brain
- Slows gastric emptying
- Regulates blood sugar
- Reduces appetite
This helps patients eat less without persistent hunger.
Mounjaro: Dual GIP + GLP-1 Action
Mounjaro activates two hormonal pathways:
- GLP-1 (as above)
- GIP (glucose-dependent insulinotropic polypeptide)
GIP enhances insulin secretion and influences fat metabolism. The combined effect creates a broader metabolic impact.
In simple terms, Wegovy acts on one hormonal pathway. Mounjaro acts on two. That additional layer of metabolic signalling appears to translate into meaningfully greater weight loss in most patients.
Mounjaro vs Wegovy Effectiveness
While population-level data favours tirzepatide, individual results vary.
- Some patients respond exceptionally well to semaglutide
- Others achieve better results with tirzepatide
- Tolerability differs between individuals
Both medications are significantly more effective than lifestyle changes alone.
The best outcomes are achieved when treatment is guided by a clinician who understands your health history and goals.
Difference Between Wegovy and Mounjaro: Dosing and Administration
Both medications are administered once weekly via subcutaneous injection using a pre-filled auto-injector pen. Both follow a gradual dose escalation protocol designed to minimise gastrointestinal side effects.
Wegovy dosing schedule:
| Week | Dose |
| Weeks 1 to 4 | 0.25mg |
| Weeks 5 to 8 | 0.5mg |
| Weeks 9 to 12 | 1.0mg |
| Weeks 13 to 16 | 1.7mg |
| Week 17 onwards | 2.4mg (maintenance) |
Mounjaro dosing schedule:
| Week | Dose |
| Weeks 1 to 4 | 2.5mg |
| Weeks 5 to 8 | 5mg |
| Weeks 9 to 12 | 7.5mg |
| Weeks 13 to 16 | 10mg |
| Weeks 17 to 20 | 12.5mg (if required) |
| Week 21 onwards | 15mg (if required and tolerated) |
Key difference:
A key difference in escalation is that Mounjaro has more dose increments, taking longer to reach its maximum therapeutic dose. This means the full effect of Mounjaro is not realised as quickly as with Wegovy. Both medications offer the option to stay at a lower dose if it is well tolerated and producing adequate results.
Mounjaro vs Wegovy Side Effects: What to Expect
Both medications have similar side effect profiles, primarily affecting the gastrointestinal system.
Common Side Effects
- Nausea
- Vomiting
- Diarrhoea or constipation
- Abdominal discomfort
- Reduced appetite
These are usually temporary and occur during dose increases.
Differences in Tolerability
- Treatment discontinuation due to side effects:
- Semaglutide: 5.6%
- Tirzepatide: 2.7%
- Semaglutide: 5.6%
- Injection site reactions:
- Tirzepatide: slightly higher
Additional Considerations
Both medications carry risks of:
- Pancreatitis
- Gallbladder issues
- Thyroid cell changes (animal studies)
Wegovy has an additional proven benefit:
- 20% reduction in cardiovascular events (SELECT trial)
Get expert guidance and find the right treatment for you.
Wegovy or Mounjaro for Weight Loss UK: Who Is Each Medication Suited For?
Both medications require a BMI of 30 or above, or a BMI of 27 or above with at least one weight-related health condition, for private prescription in the UK.
Mounjaro may be particularly suitable for:
- Patients who have not achieved adequate results with semaglutide-based treatments.
- Patients with type 2 diabetes who need both blood sugar and weight management.
- Patients who are aiming for the highest possible degree of weight reduction. Patients who have shown tolerance to GLP-1 medications previously and are seeking a more potent option.
Wegovy may be particularly suitable for:
- Patients with established cardiovascular disease who would benefit from the proven trial cardiovascular outcomes data. Patients who are cost-sensitive and cannot accommodate the price difference. Patients whose previous semaglutide use (for example Ozempic for diabetes) was well tolerated and effective. Patients who prefer a medication with a longer established record in the UK.
The best choice is always made alongside a qualified prescriber with access to your full medical history. A responsible provider will not recommend one over the other without a proper clinical assessment.
Conclusion
Wegovy and Mounjaro are among the most effective weight loss treatments currently available in the UK. Both regulate appetite through hormonal pathways and require clinical supervision.
The evidence shows that Mounjaro produces greater average weight loss. However, Wegovy offers proven cardiovascular benefits and remains a more cost-effective option.
The right choice is individual. It should be made with a qualified clinician based on your health profile and treatment goals. At Cleckheaton Pharmacy, we provide safe, structured, and clinically supervised weight loss programmes tailored to each patient.
FAQs
Is Mounjaro stronger than Wegovy?
Clinical trials show Mounjaro produces greater average weight loss. In the SURMOUNT-5 head-to-head trial, tirzepatide produced 20.2% average weight loss versus 13.7% with semaglutide over 72 weeks, making Mounjaro the more potent option by population-level data.
Can I switch from Wegovy to Mounjaro?
Switching is possible and is commonly done under clinical supervision. Patients typically begin Mounjaro one week after their last Wegovy injection, starting at an appropriate dose as guided by their prescriber. A clinical review is always required before switching.
Which has fewer side effects, Wegovy or Mounjaro?
Both have broadly similar side effect profiles. SURMOUNT-5 data showed slightly fewer treatment discontinuations due to gastrointestinal events with tirzepatide (2.7%) compared to semaglutide (5.6%), suggesting Mounjaro may be somewhat better tolerated overall despite its greater potency.
Is Wegovy cheaper than Mounjaro in the UK in 2026?
Following Eli Lilly’s September 2025 UK price increase for Mounjaro, Wegovy is now generally the more affordable option at most dose levels for private patients. Both medications cost significantly less through NHS prescription for those who qualify.
How long do I need to take these medications?
Both medications are intended for long-term use. Clinical evidence consistently shows that stopping treatment leads to weight regain as appetite returns to pre-treatment levels. Long-term treatment planning with your prescriber leads to significantly better outcomes than short courses.