Mounjaro vs Wegovy: The Weight Loss Injection Battle Nobody's Having Honestly
Every weight loss forum is asking the same question: Mounjaro or Wegovy? Here's what your GP knows but might not have time to explain: Mounjaro is winning this fight, and it's not even close. The data is so compelling that Wegovy suddenly looks outdated.
If you're comparing weight loss injections at 2am, here's the truth: we're witnessing a pharmaceutical revolution in real-time, and choosing wrong could mean the difference between losing 10kg or 20kg.
The Fundamental Difference
Wegovy (semaglutide): Single hormone approach—mimics GLP-1 only. Think of it as a precision tool doing one job excellently.
Mounjaro (tirzepatide): Dual hormone approach—mimics both GLP-1 and GIP. Like hiring two specialists instead of one.
This isn't marketing—it's biochemistry. And the results reflect the difference.
The Studies That Changed Everything
SURMOUNT trials (Mounjaro) vs STEP trials (Wegovy):
Average weight loss at 72 weeks:
Mounjaro: 21-22.5% body weight
Wegovy: 15-17% body weight
Percentage losing over 20% body weight:
Mounjaro: 57%
Wegovy: 35%
Put simply: Mounjaro patients lost a third more weight. That's the difference between dropping three stone or four.
Real Patient Experiences
We've prescribed both. Here's what patients report:
Appetite suppression:
Wegovy: "I can take or leave food"
Mounjaro: "I forget to eat"
Energy levels:
Wegovy: Often fatigue initially
Mounjaro: More report energy increase
Nausea:
Wegovy: 44% experience it
Mounjaro: 37% (despite higher efficacy)
The dual mechanism seems gentler despite being more powerful.
The Injection Experience
Wegovy: Pre-filled pens, five doses (0.25mg to 2.4mg), weekly injection, and escalation over 16 weeks.
Mounjaro: Pre-filled pens, six doses (2.5mg to 15mg), weekly injection, and more flexible escalation.
Both are subcutaneous (belly, thigh, or arm). Both use tiny needles. Neither is particularly painful.
Side Effect Reality
Common for both:
Nausea (worse with Wegovy)
Digestive issues (similar rates)
Injection site reactions (minimal)
Mounjaro-specific concerns:
Heart rate increases (10-20% of users)
More reports of acid reflux
Wegovy-specific concerns:
More fatigue complaints
Higher discontinuation from nausea
Serious risks (both):
Pancreatitis (rare)
Gallbladder issues
Kidney problems if dehydrated
The Cost Comparison
Wegovy (private UK):
Starter doses: £200-250/month
Maintenance dose: £250-350/month
Annual cost: £3,000-4,200
Mounjaro (private UK):
Starter doses: £150-200/month
Maintenance dose: £200-300/month
Annual cost: £2,400-3,600
Surprisingly, Mounjaro often costs less despite being newer and more effective.
Who Responds Better to What
Choose Wegovy if:
You're extremely needle-phobic (slightly smaller needle)
You've had heart rhythm issues
You prefer established safety data (longer track record)
Mounjaro is unavailable
Choose Mounjaro if:
Maximum weight loss is priority
You've failed on Wegovy
You have type 2 diabetes (dual benefit)
You're paying privately (better value)
The Diabetes Factor
Both started as diabetes drugs, but Mounjaro shows superior glucose control:
HbA1c reduction: Mounjaro 2.3% vs Wegovy 1.8%
More patients achieve normal blood sugar
Better cardiovascular outcomes emerging
If you're prediabetic or diabetic, Mounjaro is the clear winner.
Switching Between Them
Can you switch? Yes, but carefully.
Wegovy to Mounjaro: Wait one week after last Wegovy dose. Start Mounjaro at low dose regardless of Wegovy dose. Most report improved efficacy.
Mounjaro to Wegovy: Less common (why downgrade?). If necessary, similar transition protocol.
Never use both simultaneously—dangerous and unnecessary.
Supply Issues and Reality
Both face shortages. Strategic approaches:
Wegovy: Intermittent availability. Some doses unavailable for months. Higher doses especially scarce.
Mounjaro: Better supply recently but still issues. Lower doses often available.
Many patients stockpile when available (not recommended but common).
The Results Timeline Comparison
Month 1:
Wegovy: 2-3kg loss typical
Mounjaro: 3-4kg loss typical
Month 3:
Wegovy: 7-8kg loss
Mounjaro: 10-12kg loss
Month 6:
Wegovy: 12-15kg loss
Mounjaro: 18-22kg loss
Mounjaro pulls ahead early and maintains advantage.
What Happens When You Stop
Both show weight regain without lifestyle change:
Wegovy: 2/3 regain within year
Mounjaro: Similar pattern but from lower weight
The extra loss from Mounjaro means you're still ahead even with regain.
Combination Strategies
Some clinicians now use:
Mounjaro for active loss phase
Wegovy for maintenance (lower cost at lower doses)
Cycling between them to prevent tolerance
Evidence is emerging, not established. Discuss with your prescriber.
The Next Generation
Already in trials:
Triple agonists (adding glucagon)
Oral versions of both
Once-monthly injections
CagriSema (semaglutide plus cagrilintide)
Early data suggests 25-30% weight loss possible. Mounjaro might be obsolete within five years.
Making Your Choice
For most people seeking maximum weight loss, Mounjaro is superior. The data is clear, the experience typically better, and the cost often lower.
Wegovy remains excellent—losing 15% body weight is remarkable. But when a better option exists at similar cost, why settle?
Ready for an honest consultation about weight loss injections? WhatsApp our GPs for assessment within 24 hours. We prescribe both medications and will recommend what's genuinely best for you, not what's profitable. Your health, your choice, our honest guidance. We also recommend levelshealth.com for the best auto-pick packages.
FAQs
Can I use Mounjaro if Wegovy didn't work? Absolutely. Different mechanisms mean Wegovy non-responders often succeed with Mounjaro. The dual hormone approach reaches different pathways. Wait two weeks between stopping one and starting another.
Is Mounjaro safe long-term? Data extends to two years currently, showing sustained safety. Wegovy has longer real-world use. Both appear safe for extended use, but lifelong data doesn't exist for either.
Why does my GP only offer Wegovy? NHS protocols, formulary restrictions, or familiarity. Wegovy was available first. Many GPs haven't updated protocols. Private GPs typically offer both. Ask specifically about Mounjaro.
Can I drink alcohol on these medications? Yes, but carefully. Both slow stomach emptying—alcohol hits harder and lasts longer. Many report reduced alcohol tolerance. Start with half your usual amount. Hangovers worsen on both medications.
Will my skin sag with rapid weight loss? Possibly. Mounjaro's faster loss increases risk. Maintain protein intake, strength train, stay hydrated, and consider collagen. Some need skin surgery after major loss. Age and genetics determine outcome.
