If you have been researching weight loss treatments and wondering about the difference between Mounjaro and Wegovy, you are not alone — it is one of the questions we are asked most often at our clinic. Both are once-weekly injectable medicines approved by the MHRA and NICE for weight management in the UK, but they work in slightly different ways and have different clinical profiles that may make one more suitable for you than the other. Mounjaro (tirzepatide) activates two hormone receptors — GIP and GLP-1 — while Wegovy (semaglutide) activates only the GLP-1 receptor, and this difference in mechanism is reflected in their clinical trial results. Fishguard Pharmacy offers both Mounjaro and Wegovy as part of a fully supported, locally delivered weight management service, with our experienced team on hand to help you find the right option for your individual circumstances.
Book a consultation with Fishguard Pharmacy today and find out which weight loss treatment is right for you.
Key takeaways
- Both Mounjaro and Wegovy are once-weekly injectable weight loss treatments approved by the MHRA and NICE for use in eligible adults in the UK.
- Mounjaro (tirzepatide) is a dual GIP/GLP-1 receptor agonist, while Wegovy (semaglutide) is a GLP-1 receptor agonist only — this difference in mechanism influences their respective level of effectiveness.
- In their respective clinical trials, Mounjaro demonstrated average weight loss of up to 22.5% at the highest dose in SURMOUNT-1, while Wegovy demonstrated approximately 15% in STEP 1 — however these trials had different designs and populations and the figures should not be read as a direct head-to-head comparison.
- Both treatments are prescription-only medicines and require a thorough medical assessment before any prescription can be issued.
- The right treatment for you will depend on your individual health circumstances, eligibility, and personal goals — a qualified healthcare professional is best placed to guide that decision.
- Both treatments work best when combined with a calorie-controlled diet and regular physical activity as part of a broader, supported weight management programme.
How Do Mounjaro and Wegovy Work?
Understanding how each treatment works is the starting point for understanding why they differ in effectiveness and suitability.
Mounjaro (Tirzepatide)
Mounjaro works by activating two incretin hormone receptors — GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1). Both of these hormones are naturally released by the gut after eating, and by mimicking them simultaneously, Mounjaro delivers a stronger combined signal to the brain and digestive system. The result is a more powerful reduction in appetite, greater slowing of gastric emptying, and improved regulation of blood sugar levels. It is this dual mechanism that is believed to be responsible for the greater levels of weight loss seen in Mounjaro’s clinical trials compared to GLP-1-only treatments.
Wegovy (Semaglutide)
Wegovy works by mimicking the GLP-1 hormone only, activating GLP-1 receptors in the brain and digestive system to reduce hunger, increase feelings of fullness, and slow the rate at which food leaves the stomach. While it uses a single rather than dual mechanism, Wegovy has a very strong clinical evidence base and has been shown to produce significant, sustained weight loss in the majority of patients who use it alongside lifestyle changes. For many patients, it remains a highly effective and well-tolerated first-line treatment option.
Contact us to find out which treatment is right for you.
Which Weight Loss Treatment Produces Better Results?
Based on available clinical trial data, Mounjaro has demonstrated greater average weight loss than Wegovy. In the SURMOUNT-1 trial, participants taking the highest dose of tirzepatide (15 mg) lost an average of 22.5% of their body weight over 72 weeks — results that were previously only associated with bariatric surgery. In the STEP 1 trial for Wegovy, participants lost an average of approximately 15% of their body weight over 68 weeks at the full maintenance dose. However these trials had different designs and populations and the figures should not be read as a direct head-to-head comparison.
It is important to note that these figures come from specific trial populations and that individual results will always vary significantly depending on factors such as starting weight, adherence to the treatment programme, dietary changes, and physical activity levels. A higher average result in a clinical trial does not automatically mean that Mounjaro is the right choice for every patient — the most effective treatment is the one that is most appropriate and well-tolerated for your specific circumstances.
Mounjaro and Wegovy Side Effects
Both Mounjaro and Wegovy share a similar side effect profile, as both act on the GLP-1 receptor. The most commonly reported side effects for both treatments include nausea, vomiting, diarrhoea, and constipation, particularly during the early dose-escalation phase. These effects are generally mild to moderate and tend to improve as the body adjusts to the medication over the first few weeks.
Some patients report differences in tolerability between the two treatments, though individual experience varies considerably and no firm conclusions can be drawn from current evidence. As with any medicine, individual experience of side effects varies considerably, and your prescriber will monitor you closely throughout your treatment to ensure any issues are identified and managed promptly.
Which Weight Loss Treatment Should I Choose?
The honest answer is that the right treatment for you is the one that your prescriber recommends following a thorough review of your medical history, current health conditions, medications, and weight loss goals. There is no single answer that applies to every patient, and attempting to self-select between these two treatments without professional guidance carries real risks.
That said, there are some general considerations that often inform the decision. Mounjaro may be particularly well-suited to patients with type 2 diabetes, given that it is also licensed for glycaemic management. Wegovy may be preferred in patients who have responded well to GLP-1 treatment in the past or who have specific clinical reasons for avoiding the dual GIP/GLP-1 mechanism. In all cases, the decision should be made in partnership with a qualified healthcare professional — not based on online comparisons or social media recommendations.
Call our team at Fishguard Pharmacy today and let us help you make the right choice with confidence.
Frequently Asked Questions
We have put together answers to the questions our patients ask us most when considering Mounjaro and Wegovy.
Can I switch from Wegovy to Mounjaro?
It is possible to switch between treatments, but this should only be done under the supervision of a qualified prescriber who can assess whether a switch is clinically appropriate and manage the transition safely. Switching between GLP-1 and dual GIP/GLP-1 treatments requires careful consideration of your current dose, progress, and any side effects you have experienced.
Is Mounjaro stronger than Wegovy?
Clinical trial data suggests that Mounjaro produces greater average weight loss than Wegovy at their respective highest doses, which is thought to be related to its dual GIP/GLP-1 mechanism. However, “stronger” does not necessarily mean “better” for every patient — the most appropriate treatment depends on your individual health profile, eligibility, and how your body responds to the medication.
Are the side effects of Mounjaro and Wegovy the same?
Both treatments share a broadly similar side effect profile, with gastrointestinal symptoms such as nausea, vomiting, and constipation being the most commonly reported for both. Individual experiences vary considerably, and your prescriber will monitor you throughout your treatment to help manage any side effects that arise.
Which treatment is available on the NHS?
Both Mounjaro and Wegovy have been approved by NICE and are available through some NHS specialist weight management services, though access varies by area and NHS availability for both treatments continues to develop across Wales and England. Many patients currently access both treatments privately through regulated local pharmacies such as Fishguard Pharmacy — speak to your GP or local pharmacy for the most up to date information on NHS availability in your area.
Do both treatments require the same eligibility criteria?
Both treatments require a BMI assessment and a review of any weight-related health conditions, but the specific eligibility thresholds and criteria can differ between treatments and between the services through which they are accessed. Your pharmacist or prescriber will confirm the exact criteria that apply to you during your consultation.
How long will I need to take either treatment?
Both Mounjaro and Wegovy are intended for long-term use as part of a structured weight management programme, and the duration of treatment will depend on your individual progress, goals, and clinical circumstances. Research shows that stopping treatment without maintaining the lifestyle changes made during the programme typically leads to gradual weight regain, which is why ongoing support and a focus on lasting lifestyle habits is so important.
Make the Right Choice for Your Weight Management
While understanding the difference between Mounjaro and Wegovy is useful, the most important step you can take is speaking to a qualified healthcare professional who can make a personalised recommendation based on your health and goals. Our experienced team at Fishguard Pharmacy offers face-to-face consultations where we take the time to review your health history, walk you through your options, and recommend the treatment that is genuinely right for you.
Both treatments are available locally through Fishguard Pharmacy as part of a fully supported weight management programme, so whichever option is right for you, you can access it safely, confidently, and close to home. Getting started is as simple as picking up the phone.
Book a consultation today and we will help you find the treatment that is right for you.
Disclaimer: The information contained in this blog post is intended for general informational purposes only and does not constitute medical advice. Mounjaro and Wegovy are prescription-only medicines, and you should always speak to a qualified medical professional before starting any new treatment or making changes to your current medication. Individual eligibility, suitability, and results will vary. Please consult your GP, pharmacist, or another registered healthcare provider to discuss which treatment, if any, is appropriate for your specific circumstances.