Mounjaro vs Wegovy vs Ozempic: UK Comparison 2026
Which GLP-1 Medication Is Right For You?
Three names dominate weight loss medication in 2026: Mounjaro, Wegovy, and Ozempic. All are GLP-1 receptor agonists, but they're not identical.
This guide compares effectiveness, side effects, cost, and availability to help you understand your options.
Quick Comparison
| Factor | Mounjaro (Tirzepatide) | Wegovy (Semaglutide 2.4mg) | Ozempic (Semaglutide 1mg) | |--------|------------------------|---------------------------|---------------------------| | Active ingredient | Tirzepatide | Semaglutide | Semaglutide | | Typical weight loss | 20-22% | 15-17% | 10-12% | | NICE approved | ✅ Yes (2024) | ✅ Yes | ❌ Off-label | | NHS availability | Limited | Limited | Rare | | Private cost | £150-250/month | £120-200/month | £100-150/month | | Injection frequency | Weekly | Weekly | Weekly | | Dual action | GIP + GLP-1 | GLP-1 only | GLP-1 only |
Bottom line: Mounjaro shows superior weight loss in trials, but availability varies.
How They Work
GLP-1 Receptor Agonists (All Three)
GLP-1 (glucagon-like peptide-1) is a hormone that:
- Slows gastric emptying (you feel full longer)
- Reduces appetite (via hypothalamus signalling)
- Improves insulin sensitivity
- Reduces glucagon secretion
Result: Less hunger, better blood sugar control, weight loss.
Mounjaro's Advantage: Dual Action
Mounjaro (Tirzepatide) activates TWO receptors:
- GLP-1 receptor — appetite, fullness
- GIP receptor — amplifies insulin secretion
Why this matters:
- Greater weight loss (SURPASS trials: up to 22%)
- Better blood glucose control
- Potentially fewer GI side effects
Clinical trial comparison:
- Mounjaro: 15mg = 22.5% weight loss (SURMOUNT-1)
- Wegovy: 2.4mg = 15.2% weight loss (STEP-1)
- Ozempic: 1mg = 10-12% weight loss (STEP-5)
Mounjaro is more effective, but newer and more expensive.
Effectiveness Comparison
Mounjaro (Tirzepatide)
SURMOUNT-1 Trial (72 weeks):
- Average weight loss: 20-22%
- 15mg dose: 22.5% weight loss
- 10mg dose: 21.4% weight loss
- 5mg dose: 16.0% weight loss
Real-world UK data:
- Early 2024 launch, limited data
- Anecdotal reports: 1.5-2.5 stone typical
- Most effective for BMI >35
Wegovy (Semaglutide 2.4mg)
STEP-1 Trial (68 weeks):
- Average weight loss: 15.2%
- 86% of participants lost ≥5%
- 67% lost ≥10%
- 50% lost ≥15%
Real-world UK data (2023-2024):
- Consistent 12-18% weight loss
- 1-2 stone typical in first 6 months
- Good maintenance after 1 year
Ozempic (Semaglutide 1mg)
STEP-5 Trial (2 years):
- Average weight loss: 10-12%
- SUSTAIN trials: 6-9% at lower doses
Real-world use:
- Originally diabetes drug
- Off-label for weight loss
- Less effective than Wegovy (lower dose)
- Often used when Wegovy unavailable
Side Effects Comparison
Common Side Effects (All Three)
GI effects (most common):
- Nausea: 15-44%
- Diarrhoea: 10-30%
- Vomiting: 5-15%
- Constipation: 5-15%
Other:
- Injection site reactions: 5-10%
- Headache: 5-15%
- Fatigue: 5-10%
Mounjaro Specific
Slightly different profile due to dual action:
- May have fewer GI side effects at equivalent efficacy
- More effective at lower doses
- Nausea typically resolves within 4-8 weeks
Wegovy/Ozempic
Similar profiles:
- Ozempic (1mg) slightly fewer side effects than Wegovy (2.4mg)
- Dose-dependent: higher dose = more side effects
- Nausea peaks week 4-8
Serious Side Effects (Rare, All Three)
- Pancreatitis (0.1-0.5%)
- Gallbladder issues (cholelithiasis)
- Severe hypoglycemia (if on other diabetes meds)
- Thyroid C-cell tumours (animal studies, human risk unclear)
Contraindications:
- Personal/family history of medullary thyroid carcinoma
- MEN2 (multiple endocrine neoplasia syndrome)
- Pregnancy/breastfeeding
Cost in the UK
NHS Availability (Limited)
Wegovy:
- NICE approved March 2023
- NHS rollout: Very limited (specialist centres only)
- Criteria: BMI ≥35 + weight-related comorbidity
- 2-year maximum treatment
- Long waiting lists (12-24 months in some areas)
Mounjaro:
- NICE approved September 2024
- NHS availability: Extremely limited initially
- Similar criteria to Wegovy expected
Ozempic:
- Not NICE approved for weight loss
- NHS: Diabetes treatment only
- Weight loss: Private only
Reality: Most people access privately.
Private Costs (Monthly)
| Medication | Low | Typical | Premium | |------------|-----|---------|---------| | Mounjaro | £150 | £200 | £250+ | | Wegovy | £120 | £160 | £200+ | | Ozempic | £100 | £130 | £150+ |
Price factors:
- Clinic brand (premium vs budget)
- Included services (consultations, blood tests)
- Prescription vs full service
- Location (London premium)
Typical annual cost: £1,500-3,000 (depending on medication)
How to Get Prescribed in the UK
NHS Route (Limited)
- GP referral — Discuss weight and health
- Meet criteria — BMI ≥35 + comorbidity (or BMI ≥30 with significant health risk)
- Specialist referral — Endocrinologist or weight management clinic
- Waiting list — 12-24 months typical
- Treatment — 2 years maximum
Success rate: Low due to strict criteria and long waits.
Private Route (Most Common)
- Online clinic — e.g., [Boots Online Doctor], [Pharmacy2U]
- Private GP — Harley Street or local private practice
- Weight loss clinic — Specialist providers
Process:
- Medical questionnaire
- Video/phone consultation
- Prescription issued
- Medication delivered
- Follow-up monitoring
[Compare private clinics →]
Which Should You Choose?
Choose Mounjaro If:
- ✅ You want maximum weight loss (22% possible)
- ✅ You have significant weight to lose (BMI >35)
- ✅ You can afford £200+/month
- ✅ You don't mind newer medication (less long-term data)
Choose Wegovy If:
- ✅ You want proven effectiveness (15% typical)
- ✅ You prefer established medication
- ✅ You want potentially fewer supply issues
- ✅ NHS access might be possible eventually
Choose Ozempic If:
- ✅ You want lower cost option
- ✅ Wegovy/Mounjaro unavailable
- ✅ You're comfortable with off-label use
- ✅ You want to start with lower dose
Dosage and Administration
Starting Protocol (All Three)
Titration schedule:
- Start low to minimise side effects
- Increase every 4 weeks
- Maintenance dose: varies by medication
Example (Mounjaro):
- Week 1-4: 2.5mg
- Week 5-8: 5mg
- Week 9-12: 7.5mg
- Continue titrating to 10mg, 12.5mg, 15mg (max)
Same principle for Wegovy/Ozempic — gradual dose escalation.
Supply and Availability Issues
UK Market (2024-2026)
Wegovy:
- 2023 launch, high demand
- Supply constraints throughout 2024
- Improving in 2025-2026
Mounjaro:
- 2024 launch, limited supply initially
- Expected to improve throughout 2026
- Higher demand due to superior efficacy
Ozempic:
- Diabetes supply prioritised
- Weight loss prescriptions limited
- Often unavailable
Strategy:
- Apply to multiple clinics
- Consider starting with whatever is available
- Switch medications if supply issues
Real-World Expectations
Month 1-3
What to expect:
- Significant appetite reduction
- Possible nausea/digestive issues
- 5-10% weight loss typical
- Adjustment period
Month 3-6
What to expect:
- Side effects usually resolved
- Steady weight loss
- 10-15% total weight loss
- Lifestyle changes easier
Month 6-12
What to expect:
- Approach goal weight or plateau
- 15-20% total weight loss (Mounjaro/Wegovy)
- Maintenance planning
- Possible dose adjustment
FAQ
Can I switch between medications? Yes, but titrate up again. Don't switch abruptly — start at low dose.
What if I stop taking it?
- Weight typically regained within 6-12 months
- Appetite returns to baseline
- Metabolic adaptation reverses
- Long-term maintenance strategies needed
Is Mounjaro worth the extra cost? If you can afford it and need significant weight loss, yes. 22% vs 15% is meaningful for BMI >35.
Will NHS fund these? Extremely limited. Most people access privately.
Are there cheaper alternatives? Saxenda (liraglutide) — daily injection, less effective, about £200/month. Generally not preferred.
What about compounded versions? Unregulated, variable quality, not recommended. Use branded medication from licensed pharmacies.
Summary
| Your Situation | Recommendation | |----------------|----------------| | Maximum weight loss needed | Mounjaro (if affordable) | | Proven, reliable option | Wegovy | | Budget-conscious | Ozempic or wait for NHS | | BMI 30-35 | Any will work, Wegovy most cost-effective | | BMI >35 | Mounjaro superior efficacy |
The reality: All three work. Mounjaro is most effective but newest. Wegovy is the proven middle ground. Ozempic is budget-friendly but less effective.
Consult a doctor to determine which is appropriate for your specific situation.
Related Articles
- What to Expect in Your First Month on GLP-1
- GLP-1 Side Effects: Complete Guide
- Best UK Clinics for GLP-1
- How to Get Prescribed Weight Loss Medication
Last updated: April 2026 Medical disclaimer: This information is for educational purposes. Consult a healthcare provider before starting any medication.