Mounjaro vs Wegovy: Which Is Better for Weight Loss in the UK?
A head-to-head comparison based on SURMOUNT-5 trial data, mechanism differences, real Slinic pricing, and how UK patients should think about choosing between them.
Clinically reviewed by
Shadeia Younis, Superintendent Pharmacist (GPhC 2052119)
Prescription weight loss injections such as Mounjaro and Wegovy are now widely available in the UK as treatments for people who have struggled to achieve or maintain weight loss through lifestyle changes alone.
With both medications available privately, many UK patients reach the same question: “Which one is better?”
As of 2025, that question has a clearer answer than ever before — the SURMOUNT-5 head-to-head trial directly compared the two drugs and provided the strongest evidence so far. This guide explains what SURMOUNT-5 found, how the mechanisms differ, what to expect day-to-day on each, real Slinic pricing for both, and how to think through the right choice for your situation.
Part of our wider guide
For the broader overview of weight loss injections in the UK, see the pillar guide: Weight Loss Injections UK: Complete Clinician-Led Guide.
The Short Answer — Mounjaro vs Wegovy
- SURMOUNT-5 head-to-head (NEJM 2025): Mounjaro produced ~20.2% weight loss vs ~13.7% for Wegovy over 72 weeks
- Mechanism: Mounjaro acts on both GIP and GLP-1 receptors (dual). Wegovy acts on GLP-1 alone
- Dose range: Mounjaro 2.5mg → 15mg | Wegovy 0.25mg → 2.4mg (both weekly)
- Slinic pricing: Mounjaro £139-£285/month | Wegovy £99.99-£209.99/month
- Side effects: Broadly similar profiles (both GI-dominant); discontinuation rates comparable
- For most patients without contraindications, Mounjaro is now often the first-line choice based on outcomes
- Wegovy remains a strong option with a longer track record and is still preferred for some clinical situations
What’s on this page
- 1How Mounjaro and Wegovy Work
- 2SURMOUNT-5: The Direct Head-to-Head Trial
- 3Wider Trial Data Compared
- 4Dosing and Treatment Journey
- 5What Each Feels Like Day-to-Day
- 6Side Effects and Tolerability
- 7Cost Comparison at Slinic
- 8Contraindications Compared
- 9How to Decide Which Is Right for You
- 10Switching Between Treatments
- 11Frequently Asked Questions
How Mounjaro and Wegovy Work
Both medications support weight loss by influencing appetite regulation and digestion, but they target different combinations of receptors — which is the underlying reason for the outcome differences seen in trials.
Tirzepatide — dual GIP/GLP-1 agonist
- Activates both GLP-1 receptors (like Wegovy) and GIP receptors (additional mechanism)
- GIP activation influences energy balance, insulin sensitivity, and fat metabolism
- The combined dual-receptor action produces stronger appetite suppression and weight loss
- Manufactured by Eli Lilly
- Licensed in UK for weight management since 2023
Semaglutide — GLP-1 receptor agonist
- Activates GLP-1 receptors only — the established mechanism
- Slows gastric emptying, reduces appetite, modulates reward responses to food
- The single-receptor mechanism is highly effective but less potent than dual-action
- Manufactured by Novo Nordisk
- Licensed in UK for weight management since 2021, available from September 2023
What both share
Despite their differences, both are taken once weekly by subcutaneous injection, require gradual dose escalation (titration), are licensed alongside a reduced-calorie diet and physical activity, have similar long half-lives (~5-7 days), and have similar gastrointestinal side effect profiles.
SURMOUNT-5: The Direct Head-to-Head Trial
Until 2025, comparisons between Mounjaro and Wegovy relied on indirect data from separate trials. That changed with the publication of SURMOUNT-5 in the New England Journal of Medicine.
SURMOUNT-5 was the first major head-to-head trial directly comparing tirzepatide (Mounjaro) and semaglutide (Wegovy) at their maximum tolerated doses in adults with obesity. The trial enrolled over 700 participants without diabetes and ran for 72 weeks of active treatment.
SURMOUNT-5 results
| Outcome | Mounjaro (tirzepatide) | Wegovy (semaglutide) |
|---|---|---|
| Average weight loss (72 weeks) | ~20.2% | ~13.7% |
| Difference | ~6.5 percentage points in favour of Mounjaro | |
| Discontinuation due to side effects | Broadly comparable | Broadly comparable |
| Side effect profile | GI-dominant (similar) | GI-dominant (similar) |
This was a clean, prospective, randomised comparison — the gold standard of evidence. The 6.5 percentage point difference is clinically meaningful: for a 100kg patient, that’s the difference between losing ~14kg and losing ~20kg.
SURMOUNT-5 is the data point that genuinely answers “which is better for weight loss on average?” — and the answer is Mounjaro. But “on average” is the key qualifier — individual response varies in both directions.
Wider Trial Data Compared
SURMOUNT-5 is the most important comparison, but each drug also has its own pivotal trial worth knowing.
| Trial | Medication | Average Weight Loss | Duration |
|---|---|---|---|
| SURMOUNT-5 (NEJM 2025) | Mounjaro vs Wegovy direct | 20.2% vs 13.7% | 72 weeks |
| SURMOUNT-1 (NEJM 2022) | Mounjaro 15mg | ~22.5% | 72 weeks |
| SURMOUNT-1 (NEJM 2022) | Mounjaro 10mg | ~19.5% | 72 weeks |
| SURMOUNT-1 (NEJM 2022) | Mounjaro 5mg | ~15% | 72 weeks |
| STEP-1 (NEJM 2021) | Wegovy 2.4mg | ~15% | 68 weeks |
| STEP 8 (JAMA 2022) | Wegovy vs Saxenda | 15.8% vs 6.4% | 68 weeks |
These are population averages, not predictions. Some patients lose substantially more than these figures; some lose less. Around 32% of patients in STEP-1 (Wegovy) lost ≥20% body weight. SURMOUNT-1 (Mounjaro) showed similar response variability.
For full Wegovy trial detail: How fast can you lose weight on Wegovy?
Thinking About Starting Treatment?
The Slinic online consultation takes around three minutes. A pharmacist reviews your information within 24 hours — and pricing is transparent from the first dose.
Start Your Confidential ConsultationDifferences in Dosing and Treatment Journey
Both use gradual dose escalation, but the schedules differ significantly.
2.5mg → 15mg, 6 dose steps
- Starter dose: 2.5mg (4 weeks)
- Step 2: 5mg
- Step 3: 7.5mg
- Step 4: 10mg
- Step 5: 12.5mg
- Maintenance: up to 15mg
- Total titration: typically 20-24 weeks to maximum dose
- Patients can hold at a lower dose if appetite control is already sufficient
0.25mg → 2.4mg, 5 dose steps
- Starter dose: 0.25mg (4 weeks)
- Step 2: 0.5mg
- Step 3: 1mg
- Step 4: 1.7mg
- Maintenance: 2.4mg
- Total titration: 16 weeks to maintenance dose
- Cleaner, more predictable schedule
Practical implications:
- Wegovy reaches maintenance dose faster (16 weeks vs 20-24 weeks for Mounjaro)
- Mounjaro’s 6-step titration gives more flexibility to find the right dose
- Many Mounjaro patients respond well at intermediate doses (7.5-10mg) and don’t need to reach 15mg
- Both can be paced more slowly if side effects are problematic
Full guides: Mounjaro dosing schedule | Wegovy dosages 0.25mg to 2.4mg.
What Each Feels Like Day-to-Day
Common patient descriptions
- Stronger, more noticeable appetite suppression
- Food cravings often described as “disappearing”
- Distinct quietening of food-related thoughts (“food noise”)
- More pronounced changes at higher doses (10mg+)
- Some patients report stronger satiety from very small meals
- Greater weight loss over comparable timeframes
Common patient descriptions
- Gradual, predictable appetite reduction
- Feeling full sooner from meals
- Smaller, steadier changes over time
- Often described as “subtle but consistent”
- More established titration tolerance patterns
- Stable, predictable maintenance experience
Neither experience is universal — and neither is inherently better. Some patients prefer the more gradual feel of Wegovy; others want the stronger effect of Mounjaro.
Side Effects and Tolerability
Both medications share similar side effect profiles. In SURMOUNT-5, side effect rates and treatment discontinuation rates were broadly comparable.
Common side effects (both medications)
- Nausea — most common, typically peaks at dose increases
- Diarrhoea
- Constipation
- Vomiting
- Abdominal pain
- Reduced appetite (this is the intended effect, but can feel like a side effect if pronounced)
- Headache and fatigue (early treatment)
- Injection site reactions (usually minor)
Most side effects are mild to moderate, peak during titration, and improve as the body adjusts. Discontinuation rates due to side effects in trials are typically 4-7% — meaning most patients tolerate treatment well enough to continue.
Practical guidance:
Cost Comparison at Slinic
Cost is often a factor in the decision between the two. Slinic publishes pricing transparently for both medications — all prices include clinical assessment, follow-up support, and delivery.
Slinic monthly pricing
| Dose Equivalent Position | Mounjaro | Wegovy |
|---|---|---|
| Starter dose | 2.5mg — £139/month | 0.25mg — £99.99/month |
| Early titration | 5mg — £165/month | 0.5mg — £109.99/month |
| Mid titration | 7.5mg — £225/month | 1mg — £114.99/month |
| Later titration | 10mg — £255/month | 1.7mg — £159.99/month |
| Higher dose | 12.5mg — £275/month | — |
| Maintenance dose | 15mg — £285/month | 2.4mg — £209.99/month |
Wegovy is roughly £75-£100/month cheaper at the maintenance dose. Over a full year, that’s a meaningful difference — though so is the ~6.5 percentage point difference in average weight loss outcomes.
Detailed pricing guides: Mounjaro cost UK 2026 | Wegovy cost UK 2026.
Contraindications Compared
The contraindications for both medications are similar, reflecting their shared GLP-1 mechanism. A clinical consultation will screen for all of these.
Shared contraindications (both Mounjaro and Wegovy)
- Personal or family history of medullary thyroid carcinoma (MTC)
- Multiple Endocrine Neoplasia syndrome type 2 (MEN-2)
- Known hypersensitivity to the active ingredient
- Pregnancy or breastfeeding — both should be stopped at least 2 months before planning pregnancy
- Active eating disorders
- Severe gastroparesis or significant gastrointestinal disease
- History of pancreatitis requires individualised assessment
Mounjaro-specific considerations
- Mounjaro’s GIP activation may have slightly different effects on certain metabolic conditions — assessed case by case
- UK supply has historically been more constrained than Wegovy
Wegovy-specific considerations
- Wegovy has a longer real-world safety track record (available in some markets since 2021)
- UK supply has generally been more consistent than Mounjaro
How to Decide Which Is Right for You
Choosing between Mounjaro and Wegovy isn’t about chasing the highest percentage — it’s about selecting a treatment that fits your health profile and can be maintained.
Mounjaro may be the better choice if:
- You want the strongest available weight loss outcome on average
- You don’t have specific contraindications
- You have a higher BMI where the additional weight loss matters more clinically
- You can absorb the slightly higher monthly cost
- You’re willing to navigate the longer 6-step titration
Wegovy may be the better choice if:
- You prefer the more established (longer real-world track record) GLP-1 mechanism
- Monthly budget is a significant factor
- You want a faster, simpler titration to maintenance dose
- Mounjaro supply is constrained in your region
- Average outcomes in the 13-17% range would meet your goals
The practical clinical default in 2026
For patients without specific contraindications and where cost is not the deciding factor, Mounjaro is now often the first-line choice based on the SURMOUNT-5 outcome data. But this is not absolute — many patients do exceptionally well on Wegovy, and “average outcomes” don’t predict individual response.
A prescriber will consider your full medical history, current medications, tolerance and side-effect risk, lifestyle, goals, and budget when guiding the decision.
Switching Between Treatments
Some patients begin on one medication and later switch. Common scenarios include:
- Switching from Wegovy to Mounjaro — usually for stronger weight loss outcomes after a plateau or insufficient response
- Switching from Mounjaro to Wegovy — sometimes for tolerance reasons, cost, or supply constraints
- Switching between manufacturers due to UK supply availability
Switching should always be clinician-guided to ensure safe timing and appropriate dose conversion. The doses don’t translate directly — for example, Wegovy 2.4mg is not equivalent to Mounjaro 2.5mg despite the similar number.
For full detail: Can you switch from Wegovy to Mounjaro safely? and Swapping from Mounjaro to Wegovy.
Clinician-Led Care at Slinic
At Slinic, treatment choice is guided by clinical suitability — not trends or which medication generates more margin. Both Mounjaro and Wegovy are available, both are clinically supported, and the choice is made with the patient based on the full picture.
Shadeia Younis
Superintendent Pharmacist, Slinic (GPhC 2052119)
The Mounjaro vs Wegovy decision is rarely binary. Patients arrive with different starting points, different clinical histories, and different budgets — and the right answer depends on all of them.
Slinic patients have access to genuinely impartial clinical guidance: the conversation is about what’s clinically best for the patient, not which medication we’d rather dispense. That oversight is led by Shadeia Younis, our superintendent pharmacist.
With Slinic, you’ll receive
- Impartial guidance on which medication best suits your situation
- Clear explanations of how each treatment works and what the trial data shows
- Both Mounjaro and Wegovy available — Mounjaro £139-£285/month, Wegovy £99.99-£209.99/month
- Pharmacist-led clinical review at every dose change
- Support if you want to switch between medications after starting
- Genuine UK-licensed medication from Eli Lilly (Mounjaro) or Novo Nordisk (Wegovy)
Related Guides From Slinic
These guides go deeper on the topics most patients consider alongside the Mounjaro vs Wegovy decision.
Medical references and guidance
Clinical comparisons in this article are based on SURMOUNT-5 (Aronne et al., NEJM 2025) — the direct head-to-head trial of tirzepatide vs semaglutide; SURMOUNT-1 (Jastreboff et al., NEJM 2022) for Mounjaro outcome data; STEP-1 (Wilding et al., NEJM 2021) for Wegovy outcome data; STEP 8 (Rubino et al., JAMA 2022) for Wegovy vs Saxenda data; the MHRA Summary of Product Characteristics for both Mounjaro (tirzepatide) and Wegovy (semaglutide); and General Pharmaceutical Council standards for online prescribing. All medical facts in Slinic content are verified against MHRA, NICE, NHS, BNF, and peer-reviewed sources.
Frequently Asked Questions
In the SURMOUNT-5 head-to-head trial (NEJM 2025), Mounjaro (tirzepatide) produced ~20.2% average weight loss compared to ~13.7% for Wegovy (semaglutide) over 72 weeks. On average, Mounjaro produces stronger weight loss outcomes, but individual response varies and Wegovy remains a strong option — particularly for patients who tolerate the GLP-1 mechanism well or have specific clinical reasons to prefer it. A consultation determines the right choice.
Not always. SURMOUNT-5 showed Mounjaro outperformed Wegovy on average (~20.2% vs ~13.7%), but individual outcomes vary significantly based on dose tolerated, adherence, lifestyle factors, and biological response. Some patients respond exceptionally well to Wegovy, and some patients tolerate Wegovy better than Mounjaro.
Both medications are licensed and prescribed under the same UK safety standards. Wegovy has been available longer in some markets (since 2021), giving it a longer real-world safety track record, but both have robust trial data and post-marketing surveillance. Neither is inherently safer than the other in clinical assessment.
Yes — switching is clinically possible with prescriber guidance to ensure safe timing and dose conversion. Patients sometimes switch from Wegovy to Mounjaro for greater weight loss outcomes, or in the opposite direction if tolerance issues arise. The switch should always be supervised by a prescriber. See our switching guide.
The side effect profiles are similar, dominated by gastrointestinal effects (nausea, diarrhoea, constipation, vomiting). In SURMOUNT-5, side effect rates and discontinuation rates were broadly comparable between the two drugs. Individual tolerability varies — some patients tolerate one significantly better than the other.
A clinical consultation is the best way to decide. For patients without specific contraindications, Mounjaro is often the first-line choice based on superior weight loss outcomes. Wegovy may be preferred for patients with longer treatment continuity needs, specific clinical reasons, or when Mounjaro supply is constrained. The consultation considers your medical history, tolerance, goals, and budget.
At Slinic, Mounjaro ranges from £139/month (2.5mg starter) to £285/month (15mg maintenance). Wegovy ranges from £99.99/month (0.25mg starter) to £209.99/month (2.4mg maintenance). Both include all clinical assessment and follow-up — no separate consultation or delivery fees.
Choose With Clinical Confidence
The Slinic consultation takes around three minutes — and a pharmacist reviews your information within 24 hours to discuss which medication suits you best.
Start Your Confidential ConsultationMedical Disclaimer
This article provides comparative educational information about Mounjaro and Wegovy for UK patients and is not a substitute for professional medical advice. Both medications are prescription-only and should only be used together with a reduced-calorie diet and increased physical activity under appropriate clinical supervision. Always consult qualified healthcare providers before starting weight loss medication. Individual results vary substantially from trial averages. Prices correct as of April 2026 and may be subject to change.