Wegovy vs Mounjaro: Which Weight Loss Injection Works Best for You?
If you are considering a weight loss injection for the first time, you have likely come across two names more than any others: Wegovy and Mounjaro. Both are prescription-only, once-weekly injections that have changed how clinicians and patients approach obesity treatment in the UK. But they are not identical, and choosing between them is not always straightforward.
This guide breaks down everything you need to know — how they work, how much weight you can expect to lose, what side effects to watch for, how much they cost, and who each one is best suited to. By the end, you will have a clear, evidence-based picture to take into your next conversation with a healthcare professional.
What Are Wegovy and Mounjaro?
Both Wegovy and Mounjaro are injectable medications licensed in the UK for weight management in adults living with obesity or overweight with related health conditions. They belong to a class of medicines known as GLP-1 receptor agonists, which work by mimicking gut hormones that signal fullness to the brain.
Wegovy contains the active ingredient semaglutide, developed by Novo Nordisk. It received UK licensing as a weight loss treatment in 2021 and has been available for longer than Mounjaro. It is given once weekly via a pre-filled injection pen, starting at a low dose and building up gradually.
Mounjaro contains the active ingredient tirzepatide, developed by Eli Lilly. It was originally licensed in the UK to treat type 2 diabetes, and subsequently approved as a weight loss treatment. It is also a once-weekly injection using a pre-filled pen, with a similar dose escalation approach.
The key distinction between them lies in their mechanism. Wegovy works on one hormonal pathway. Mounjaro works on two.
How Do They Work?
Wegovy (Semaglutide): Single Hormone Action
Wegovy mimics GLP-1 (glucagon-like peptide-1), a hormone your body naturally releases after eating. When GLP-1 is activated:
- Your brain receives “I’m full” signals sooner
- Your stomach empties more slowly
- Blood sugar levels become better regulated
- Your overall appetite decreases
This single-pathway approach is well understood, backed by years of clinical data, and highly effective for most people.
Mounjaro (Tirzepatide): Dual Hormone Action
Mounjaro does everything Wegovy does through GLP-1, but it also activates a second receptor called GIP (glucose-dependent insulinotropic polypeptide). GIP plays a role in regulating energy storage and fat metabolism, which means:
- Appetite suppression may be stronger
- The effects on blood sugar control can be broader
- Fat storage is further inhibited
This dual action is what sets Mounjaro apart clinically, and it is why trial data tends to show higher average weight loss for Mounjaro compared to Wegovy.
Wegovy vs Mounjaro: Effectiveness Compared
This is usually the first question people ask, and the answer has evolved significantly in 2025 and 2026.
Clinical Trial Results
Treatment | Dose | Average Weight Loss | Trial Duration |
Wegovy (semaglutide) | 2.4mg | 13.7–17% | 68–72 weeks |
Wegovy (semaglutide) | 7.2mg (new) | ~20.7% | 72 weeks |
Mounjaro (tirzepatide) | 15mg | ~20.2% | 72 weeks |
A landmark 2025 study published in the New England Journal of Medicine (SURMOUNT-5) directly compared the two treatments. Participants on Mounjaro lost an average of 20.2% of their body weight, compared to 13.7% on the standard 2.4mg dose of Wegovy.
However, an important development in early 2026 changed the picture. A higher-strength version of Wegovy (7.2mg) received MHRA approval, and its clinical trial data showed an average weight loss of around 20.7%, which is comparable to Mounjaro’s results. This means the effectiveness gap between the two treatments has narrowed considerably.
In practical terms, both medications can help you lose a significant amount of weight when combined with healthy eating and regular exercise. Mounjaro still shows a slight edge at its maximum dose, but the difference is smaller than early comparisons suggested.
What Does This Mean for You?
If your main goal is maximum average weight loss percentage, Mounjaro’s 15mg dose has historically delivered the highest results. But if you prefer a treatment with a longer track record and now comparable top-end efficacy, the new 7.2mg Wegovy is a strong option to consider.
Side Effects: What to Expect
Because both medications work through similar mechanisms, their side effect profiles are also similar. Most side effects are digestive and tend to be most noticeable when you first start or when your dose increases.
Common Side Effects (Both Medications)
- Nausea
- Constipation or diarrhoea
- Bloating and indigestion
- Stomach discomfort
- Vomiting (less common)
These effects are generally mild and short-lived. They typically ease as your body adjusts to the medication.
Do One Have More Side Effects Than the Other?
Because Mounjaro activates two hormone receptors rather than one, it has slightly more potential to cause digestive side effects. However, clinical data shows that most people tolerate both medications well. Injection site reactions such as redness or mild discomfort were reported in about 3.2% of Mounjaro users versus 1.4% of Wegovy users in trials.
Discontinuation rates tell a useful story: roughly 4% of people stopped Wegovy (2.4mg) due to side effects, compared to 6–8.5% for Mounjaro. The newer 7.2mg Wegovy had a discontinuation rate of around 3.3%.
Important Considerations for Mounjaro Users
If you are taking Mounjaro and use oral contraceptives or oral HRT, you should be aware of a specific interaction. Tirzepatide can affect how your body absorbs oral medications. NHS guidance recommends using additional contraception (such as condoms) and switching to patch or gel forms of HRT if applicable. Always discuss this with your prescriber before starting treatment.
Dosage and Injection Schedule
Both medications follow a gradual dose escalation schedule. Starting at a lower dose reduces the risk of side effects and allows your body to adapt.
Wegovy Dosage Schedule
- Start: 0.25mg weekly
- Increases every 4 weeks
- Maximum licensed dose (standard): 2.4mg
- New higher dose: 7.2mg (available from late 2025 onward)
Mounjaro Dosage Schedule
- Start: 2.5mg weekly
- Increases every 4 weeks
- Maintenance options: 5mg or 10mg
- Maximum dose: 15mg
Both come as pre-filled, ready-to-use injection pens. You self-administer the injection once a week, on the same day each week, into the abdomen, thigh, or upper arm. No mixing or drawing up of medication is required.
Cost in the UK: Private Prescription Pricing
Most people accessing Wegovy or Mounjaro in the UK do so via a private prescription, as NHS access remains limited (more on that below).
Current Typical Pricing (2025–2026)
After Eli Lilly increased Mounjaro prices in September 2025, Wegovy became the more cost-effective option for most people at standard doses. A standard 2.4mg Wegovy course is now generally cheaper than a comparable Mounjaro course. The new 7.2mg Wegovy dose sits closer to Mounjaro pricing.
Annual costs for either treatment on a full private course can range from approximately £2,300 to £3,600 depending on dose and provider.
You should also factor in consultation fees (typically £50–£150 for an initial assessment) when budgeting for private treatment, though many online services include this in the first month cost.
NHS Access: Who Qualifies?
Access to both medications on the NHS is possible but currently limited by strict eligibility criteria and a phased rollout.
Wegovy on the NHS
Wegovy is available through NHS specialist weight management services (SWMS) for people with:
- A BMI of 35 or above (or 32.5+ for certain ethnic groups at higher risk)
- At least one weight-related health condition such as type 2 diabetes, high blood pressure, or cardiovascular disease
- Referral via your GP to a specialist clinic
NHS Wegovy prescriptions are currently limited to a maximum of two years. If eligible, you pay the standard NHS prescription charge (currently £9.90 per item) unless you are exempt.
Mounjaro on the NHS
As of March 2025, Mounjaro became available on the NHS through specialist weight management services and, on a phased basis, through GP practices. However, the NHS is currently prioritising those with the highest clinical need. To be eligible in the first phase of the rollout, you generally need:
- A BMI of 40 or above (adjusted downward for certain ethnic backgrounds)
- At least four of the following conditions: type 2 diabetes, hypertension, dyslipidaemia, established cardiovascular disease, or obstructive sleep apnoea
NHS England plans to expand access over time, with a target of reaching 220,000 people by the end of 2027. If you do not meet current NHS criteria, private prescription is the main alternative route.
Who Is Each Medication Best Suited To?
This is where a balanced, honest assessment matters most. Neither medication is universally “better” — suitability depends on your health profile, medical history, and personal circumstances.
Wegovy May Be the Better Fit If You:
- Have existing heart disease or a high cardiovascular risk (Wegovy is currently the only one of the two approved to reduce cardiovascular risk in the UK)
- Are taking the oral contraceptive pill or oral HRT and do not want to change your method
- Prefer a treatment with a longer track record of real-world use
- Are more sensitive to side effects and want the option with a slightly lower discontinuation rate
- Are managing your budget and want the most cost-effective option at standard doses
Mounjaro May Be the Better Fit If You:
- Want the highest possible average weight loss at the maximum dose
- Also have type 2 diabetes, since Mounjaro is approved to manage both conditions simultaneously
- Are comfortable with a newer treatment and the possibility of slightly more digestive side effects
- Have not responded well to semaglutide-based treatments in the past
In both cases, your prescriber will make the final clinical decision based on your full medical history. Neither should be self-selected without proper consultation.
Weight Loss Management: What Happens After You Start?
Starting either injection is only one part of a structured approach to weight loss management. Clinical guidance is clear that both medications work best when combined with:
- A reduced-calorie, balanced diet
- Regular physical activity
- Ongoing medical monitoring
Without sustainable lifestyle changes, research shows that most people regain a significant portion of lost weight within a year of stopping the medication. This is not a reflection of the medication failing — it reflects how obesity works as a long-term condition.
If you are beginning your journey and want to understand how weight loss management works in practice, it is worth speaking to a healthcare professional who can assess your eligibility and help you build a plan that extends beyond the injection itself.
Higher Crumpsall Pharmacy offers a structured weight loss management service for eligible patients in the Manchester area, providing clinical support alongside any prescribed treatment. You can also find further guidance through our dedicated weight loss clinic in Middleton and our Crumpsall weight loss service.
Wegovy vs Mounjaro: Quick Comparison Summary
Feature | Wegovy (Semaglutide) | Mounjaro (Tirzepatide) |
Mechanism | GLP-1 receptor agonist | Dual GLP-1 and GIP agonist |
Average weight loss | 13.7–20.7% | ~20.2% |
Weekly injection | Yes | Yes |
NHS availability | Via SWMS (specialist referral) | Via SWMS and some GP practices (phased) |
Private cost (monthly) | ~£105–£299 | ~£149–£375 |
Cardiovascular risk reduction | Yes (approved) | Under investigation |
Oral contraceptive interaction | None | May reduce absorption |
Licensed in UK for weight loss | Since 2021 | Since 2023 |
Side effect profile | Moderate | Moderate (slightly higher discontinuation rate) |
Frequently Asked Questions
1. Is Mounjaro stronger than Wegovy?
At its maximum 15mg dose, Mounjaro has historically shown higher average weight loss than the standard 2.4mg Wegovy dose. However, the new 7.2mg Wegovy (approved in 2026) achieves comparable average results. Both are highly effective, and individual responses vary considerably.
2. Can I switch from Wegovy to Mounjaro (or vice versa)?
Yes, switching is possible but should always be done under medical supervision. Because the two medications work differently and use different dose scales, there is no simple like-for-like dose conversion. Your clinician will assess the right starting dose based on your current treatment and response.
3. Are weight loss injections safe for long-term use?
Current evidence supports the safety of both medications for extended use, and NICE guidance recommends annual reviews to assess ongoing suitability. Both are still classified as “black triangle” drugs in the UK, meaning they are monitored more closely than established medications as longer-term real-world data continues to build.
4. What happens if I stop taking the injections?
Most people regain weight after stopping treatment, often within the first 12 months. This is because the medications suppress appetite while they are active — once they leave your system, appetite typically returns to its previous level. Building healthy habits during treatment is the most important factor in maintaining results long-term.
5. Can I get Wegovy or Mounjaro through a local pharmacy?
Both medications require a valid prescription, which can come from an NHS specialist service, your GP (for Mounjaro in some areas), or a private prescriber. Once you have a prescription, a registered pharmacy can dispense the medication. If you are in the Manchester or Crumpsall area, our team can advise on your options. You may also find our guide on how to get the most out of weight loss injections in Crumpsall helpful.
Ready to Take the Next Step?
Whether Wegovy or Mounjaro turns out to be the right fit for you, the most important next step is speaking with a qualified healthcare professional. A proper consultation will review your BMI, health history, current medications, and goals to help you make a safe and informed choice.
If you are based in Manchester or the surrounding area, our weight loss management service at Higher Crumpsall Pharmacy is here to support you.
For questions about prescriptions, eligibility, or what to expect from treatment, our team is happy to help. Visit us in Crumpsall, or find a pharmacy near you that can support your journey.
Always consult a qualified healthcare professional before starting any prescription medication.
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