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
Before you commit, compare UK clinics on price, dose options and monitoring, and read our overview of private clinics so you know what good service looks like.
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.
One thing all three have in common
Whichever medication you end up on, the weight comes off quickly, so prioritising protein helps protect lean muscle throughout.
Optimum Nutrition Gold Standard Whey 908g
24g of protein per scoop to help you hit your targets when your appetite is suppressed. Protein is the single most important lever for preserving muscle and limiting hair loss on a GLP-1.
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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.