Mounjaro vs Wegovy for Weight Loss: A Comprehensive Comparison
Mounjaro (tirzepatide) and Wegovy (semaglutide) represent the most effective weight loss medications currently available. Both are weekly injections that have revolutionised obesity treatment, but they work through different mechanisms and produce varying results. This detailed comparison will help you understand which medication might be better suited to your weight loss goals.
The Two Leading Weight Loss Medications
Mounjaro (Tirzepatide)
- Active ingredient: Tirzepatide
- Mechanism: Dual GIP/GLP-1 receptor agonist
- Doses: 2.5mg to 15mg weekly
- Approval: Diabetes (UK), Weight loss (under review)
- Average weight loss: 21% of body weight
Wegovy (Semaglutide)
- Active ingredient: Semaglutide
- Mechanism: GLP-1 receptor agonist
- Doses: 0.25mg to 2.4mg weekly
- Approval: Weight management (UK approved)
- Average weight loss: 15-17% of body weight
How They Work Differently
Wegovy: Single Hormone Approach
Wegovy mimics GLP-1 (glucagon-like peptide-1), a naturally occurring hormone that:
- Reduces appetite by acting on brain receptors
- Slows gastric emptying, keeping you fuller longer
- Improves blood sugar regulation
- Reduces food cravings
Mounjaro: Dual Hormone Approach
Mounjaro activates both GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 receptors, providing:
- Enhanced insulin secretion: Better blood sugar control
- Improved fat metabolism: More efficient fat burning
- Greater appetite suppression: Combined effect of two hormones
- Energy expenditure: May increase metabolic rate
Key Insight
Mounjaro's dual receptor activation (GIP + GLP-1) is thought to be responsible for its superior weight loss results compared to GLP-1-only medications like Wegovy. However, Wegovy has more established long-term safety data and broader approval for weight management.
Clinical Trial Results Compared
| Metric | Mounjaro (15mg) | Wegovy (2.4mg) |
|---|---|---|
| Average Weight Loss | 21% of body weight | 15-17% of body weight |
| Study Duration | 72 weeks (SURMOUNT-1) | 68 weeks (STEP 1) |
| Participants Losing ≥20% | 57% | 35% |
| Waist Circumference Reduction | -14.7 cm | -13.5 cm |
| HbA1c Improvement (diabetes) | -2.0% | -1.5% |
What Do These Numbers Mean?
For a person weighing 100kg (220 pounds):
- Mounjaro (15mg): Average loss of 21kg (46 pounds) over 72 weeks
- Wegovy (2.4mg): Average loss of 15-17kg (33-37 pounds) over 68 weeks
These are average results. Individual outcomes vary based on adherence to lifestyle changes, starting weight, metabolism, and other factors.
Side Effects and Tolerability
Common Side Effects (Both Medications)
- Nausea (most common, usually temporary)
- Diarrhoea or constipation
- Vomiting
- Abdominal pain or discomfort
- Reduced appetite
- Headache
- Fatigue
Tolerability Comparison
Mounjaro: Clinical trials showed gastrointestinal side effects in approximately 60-70% of participants, typically mild to moderate. Discontinuation rates due to adverse events were around 6%.
Wegovy: Similar gastrointestinal side effects occurred in about 50-60% of participants. Discontinuation rates were approximately 7%.
Tolerability Tips
Side effects can be minimised with:
- Gradual dose escalation
- Eating smaller, more frequent meals
- Avoiding fatty or spicy foods
- Staying well-hydrated
- Taking medication on the same day each week
Making the Right Choice for Your Journey
Consider Mounjaro If:
- You're seeking the highest possible weight loss results
- You have type 2 diabetes (currently approved for this in the UK)
- You're willing to work with a private clinic while awaiting broader approvals
- Your insurance or financial situation allows for potentially higher costs
- You prefer the latest innovation in weight loss pharmacotherapy
Consider Wegovy If:
- You prefer a medication with established weight management approval
- You want extensive long-term safety data
- You may be eligible for NHS provision (BMI ≥35 or ≥30 with comorbidities)
- You're looking for proven cardiovascular benefits
- You prefer a medication specifically designed for weight loss
Cost Considerations
Private treatment costs:
- Mounjaro: £200-£350 per month (depending on dose)
- Wegovy: £150-£250 per month
At The London Weight Loss Clinic, we offer competitive pricing with comprehensive support packages including nutritional counselling, regular monitoring, and lifestyle coaching.
Can You Switch Between Medications?
Yes, it is possible to switch between Mounjaro and Wegovy under medical supervision. Reasons for switching might include:
- Insufficient weight loss response
- Tolerability issues
- Cost or availability changes
- Personal preference
Your healthcare provider can guide you through a safe transition plan with appropriate dose adjustments.
Dr. Rabih Wassel
Chief Medical Officer • MBBS, BSc, MSc, MRCS, MRCGP
Dr. Rabih Wassel is a board-certified physician specialising in obesity medicine with over 15 years of experience in weight management and metabolic health.