Mounjaro vs Wegovy: Which Is Right for You?
Editorial TeamShare
Summary: Mounjaro (tirzepatide) and Wegovy (semaglutide) are both once-weekly prescription injections licensed in the UK for weight management. Their clinical trial results differ, but the trials weren't head-to-head, and the right treatment depends on individual health profile rather than headline numbers. A UK-registered prescriber should make the final recommendation based on your medical history and clinical suitability.
Two clinically proven treatments. One decision. If you're comparing Mounjaro and Wegovy, you've already done the hard part: you've decided that prescribed weight management is worth considering. The question now is which treatment is right for you.
Both medicines have strong clinical evidence behind them. Both are licensed in the UK for weight management. Both work through gut hormone pathways that influence appetite and blood sugar regulation. They are not identical, though, and the right choice depends on your individual health profile, not on which name you saw first.
This guide explains what each medicine is, what the trial data actually shows, and the factors a prescriber weighs when recommending one over the other. What it will not do is tell you which to take. That decision belongs with a UK-registered prescriber who has reviewed your full health information.
What is Mounjaro?
Mounjaro is the brand name for tirzepatide, a once-weekly prescription injection licensed in the UK for weight management in adults. The MHRA granted the weight management licence in November 2023, adding to its earlier licence for type 2 diabetes.
Tirzepatide works differently from other GLP-1 medicines. It's a dual GIP and GLP-1 receptor agonist, meaning it mimics two gut hormones instead of one. Activating both pathways helps reduce appetite, slow stomach emptying, and support better blood sugar regulation.
In the SURMOUNT-1 trial, adults with obesity or overweight without type 2 diabetes lost an average of 16.0% (5mg), 21.4% (10mg), and 22.5% (15mg) of body weight over 72 weeks, compared with 2.4% on placebo. The results were published in the New England Journal of Medicine in July 2022.
Dosing starts at 2.5mg weekly and titrates upward over several months based on tolerance and clinical response, with a maximum of 15mg. Mounjaro is available on the NHS through a phased GP rollout that began in June 2025, but current eligibility is restricted to adults with a BMI of 40 or above and four qualifying health conditions. For most adults, private prescription remains the primary route.
At Foundry, Mounjaro starts from £168 per month for the 2.5mg starter dose on pay-as-you-go.
What is Wegovy?
Wegovy is the brand name for semaglutide 2.4mg, a once-weekly prescription injection licensed in the UK for weight management in adults. The MHRA granted the licence in 2021, and Wegovy launched in the UK in September 2023.
Semaglutide is a GLP-1 receptor agonist. It mimics one gut hormone (GLP-1) to reduce appetite, slow gastric emptying, and support blood sugar regulation. The same active ingredient is also sold as Ozempic, though Ozempic is licensed for type 2 diabetes, not weight management.
In the STEP-1 trial, adults with obesity or overweight without type 2 diabetes lost an average of 14.9% of body weight over 68 weeks on semaglutide 2.4mg, compared with 2.4% on placebo. Longer-term STEP-5 data showed an average of 15.2% maintained over 104 weeks (two years). Both trials appeared in peer-reviewed medical journals.
Dosing starts at 0.25mg weekly and titrates gradually over 16 to 20 weeks to the maintenance dose of 2.4mg. Wegovy is available on the NHS within specialist weight management services only; GPs cannot prescribe it for weight management. Specialist waiting lists are long, so private prescription is the main route for most adults.
In April 2026, NICE published draft guidance recommending semaglutide for reducing cardiovascular risk in adults with established heart disease and BMI 27 or above. This is a separate indication from weight management.
At Foundry, Wegovy starts from £89 per month for the 0.25mg starter dose on pay-as-you-go.
How do Mounjaro and Wegovy compare?
Both medicines share a family resemblance: once-weekly injections, gradual dose titration, and similar gastrointestinal side effects. The differences sit in their mechanism, dose range, trial results, and route to prescription.
| Factor | Mounjaro (tirzepatide) | Wegovy (semaglutide) |
|---|---|---|
| Mechanism | Dual GIP and GLP-1 receptor agonist | GLP-1 receptor agonist |
| Trial weight loss (average) | 16.0% to 22.5% over 72 weeks (SURMOUNT-1) | 14.9% over 68 weeks (STEP-1); 15.2% over 104 weeks (STEP-5) |
| Dose range | 2.5mg to 15mg weekly | 0.25mg to 2.4mg weekly |
| Titration | Around five months to maximum dose | 16 to 20 weeks to maintenance dose |
| NHS availability | Phased GP rollout (BMI 40+ with four comorbidities) | Specialist weight management services only |
| Common side effects | Nausea, diarrhoea, constipation, reduced appetite | Nausea, diarrhoea, constipation, reduced appetite |
| Foundry starting price | From £168/month (2.5mg PAYG) | From £89/month (0.25mg PAYG) |
The headline weight loss figures differ, but the trials weren't head-to-head. SURMOUNT-1 and STEP-1 enrolled different populations, used different study designs, and ran for different durations. Direct numerical comparison is informative but not definitive, and the real-world result for any individual depends on adherence, dose tolerance, and lifestyle factors alongside treatment.
Side effect profiles are similar. Both medicines commonly cause gastrointestinal effects during the early weeks, particularly at dose increases. Most effects settle within the first few weeks of each dose step.
In January 2026, the MHRA updated its product information for all GLP-1 and dual GLP-1/GIP medicines (including Wegovy and Mounjaro) to highlight a small risk of severe acute pancreatitis, including rare reports of necrotising and fatal cases. Anyone taking these medicines who experiences severe, persistent stomach pain should seek urgent medical attention. Suspected side effects can be reported via the Yellow Card scheme.
Neither medicine is universally "better" than the other. They are different clinical tools with different profiles, and both work well for the right person. What matters is whether the right medicine has been matched to the right individual, at the right dose, with the right clinical support. A prescriber, not a search engine, should make the final call, because a prescriber reviews your full medical history, current medications, BMI, comorbidities, and any previous experience with weight management treatment.
Who might be better suited to each?
Every prescriber weighs factors individually, but some patterns come up more often than others. The scenarios below are general considerations, not prescriptions. A qualified clinician will always make the call based on your full profile.
A prescriber may consider Mounjaro for adults who:
- Have found previous GLP-1 treatment (such as semaglutide) insufficient for their weight management goals
- Also have type 2 diabetes, where tirzepatide's dual mechanism may offer broader metabolic benefit
- Are comfortable with a longer titration period and a wider dose range
- Want access to the higher weight loss figures shown in SURMOUNT-1
A prescriber may consider Wegovy for adults who:
- Are starting GLP-1 treatment for the first time and want to begin at a lower entry dose
- Have a history of cardiovascular disease and BMI 27 or above, where NICE's April 2026 draft guidance supports semaglutide for cardiovascular risk reduction as a separate clinical indication
- Are cost-sensitive, as Wegovy has a lower starting price at Foundry
- Prefer a treatment with longer-term (two-year) published maintenance data from STEP-5
Prior tolerance to gut-hormone medicines matters too. Some people respond well to one and struggle with the other, even though the side effect profiles look similar on paper. Real-world tolerance varies, and a prescriber will adjust treatment if side effects are persistent or severe.
None of these factors are absolute. Many adults are clinically suitable for either medicine, and the choice comes down to professional judgement. The honest answer to "which one should I take?" is usually "let's do an assessment and find out".
How Foundry approaches treatment selection
Foundry doesn't pre-select a medicine before your assessment. That's by design. Matching a treatment to a patient is a clinical decision, not a shopping preference.
Every new Foundry member completes a health assessment covering medical history, current medications, BMI, lifestyle factors, and previous experience with weight management treatment. A UK-registered prescriber reviews that information and, if treatment is clinically appropriate, recommends the medicine and starting dose suited to you. If neither Mounjaro nor Wegovy is a safe or suitable option, your prescriber will tell you and explain why.
Treatment is supplied by a GPhC-registered pharmacy partner and delivered in tracked, cold-chain packaging. Your programme includes regular clinical check-ins, dose reviews, and ongoing access to the clinical team for questions or concerns.
The Forge annual membership at £249 covers all clinical consultation and prescribing fees across the year, across every weight-management medicine on formulary. If your prescriber recommends switching medicine or adjusting dose mid-year, that's covered. You pay medication costs only, not a per-order service fee.
This model means the clinical question (which medicine suits this person?) isn't shaped by commercial pressure. The prescriber recommends what's right for you, and Foundry's role is to support that decision with regulated dispensing, clinical oversight, and practical delivery.
The bottom line
Mounjaro and Wegovy are both effective, clinically proven treatments for weight management. They work through related but distinct mechanisms, produce different headline figures in their respective trials, and are prescribed under different NHS rules. Both are available privately in the UK.
The best choice isn't found by comparing numbers. It's found by matching the right medicine to the right person, based on medical history, clinical suitability, and realistic long-term use. That's a prescriber's judgement, supported by trial evidence, not a consumer decision based on marketing.
If you're ready to move forward, the next step is a clinical assessment. Your prescriber will tell you which treatment, if any, is suitable for your situation and explain the reasoning. From there, you can start treatment with clinical support built in.
Check your eligibility and start a Foundry health assessment.
Frequently asked questions
Is Mounjaro stronger than Wegovy?
Mounjaro and Wegovy work through related but distinct mechanisms. In their respective phase 3 trials, Mounjaro (tirzepatide) showed average weight loss of up to 22.5% over 72 weeks in SURMOUNT-1, while Wegovy (semaglutide 2.4mg) showed 14.9% over 68 weeks in STEP-1. The trials weren't head-to-head, so direct comparison is limited. "Stronger" depends on the individual, not the headline figure. A prescriber will assess whether either is clinically suitable for you.
Which is cheaper, Mounjaro or Wegovy in the UK?
At Foundry, Wegovy starts from £89 per month for the 0.25mg starter dose, while Mounjaro starts from £168 per month for the 2.5mg starter dose on pay-as-you-go. Prices rise with dose as patients titrate upward. Costs also vary between providers, so the cheapest price isn't always the safest. Always check that your provider is CQC-regulated and dispenses through a GPhC-registered pharmacy.
Can I switch from Wegovy to Mounjaro?
Switching between GLP-1 medicines is possible under clinical supervision, but it isn't a decision to take lightly. Your prescriber will consider why you want to switch, your current dose, how you've tolerated treatment so far, and the appropriate starting dose on the new medicine. Switching directly at a like-for-like dose isn't safe, because the medicines have different potencies. If you're a Foundry member, your prescriber can discuss switching at any scheduled check-in.
Is Wegovy available on the NHS?
Wegovy is available on the NHS, but only through specialist weight management services, not via GPs. Referral criteria are strict and waiting lists are long. NICE TA875 (March 2023) recommends semaglutide within tier 3 or 4 specialist services for adults meeting specific BMI and comorbidity criteria. Most adults who want Wegovy access it through private prescription.
How long do I need to stay on Mounjaro or Wegovy?
Weight management with GLP-1 medicines is generally treated as long-term therapy, not a short course. Trial data from STEP-4 (semaglutide) and SURMOUNT-4 (tirzepatide) shows that stopping treatment typically leads to significant weight regain. Ongoing use with periodic clinical review is the current clinical consensus, though maintenance strategies vary by individual. Your prescriber will discuss long-term plans as part of your programme.
Treatment is subject to prescriber approval and clinical suitability. Results vary between individuals. Prices shown are Foundry's pay-as-you-go starting prices for the lowest dose of each medicine and exclude shipping.