Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are highly effective weight loss injections, but clinical trial data consistently shows that Mounjaro produces greater average weight loss — with participants without type 2 diabetes losing up to 22.5% of their body weight at the highest dose, compared to around 14.9% with Wegovy. However, the “best” option for any individual depends on their health profile, medical history, and personal response to treatment, which is why a thorough consultation with a qualified clinician is always the essential first step. Both medications now have cardiovascular outcomes data — Wegovy from the SELECT trial and Mounjaro from the SURPASS-CVOT trial — making the choice between them increasingly nuanced. The team at G.M. Graham Pharmacies in Essex is here to cut through the confusion, explain the differences between Mounjaro and Wegovy, and help you find the right treatment for your needs.
Taking that first step is easier than you think. Book an appointment with our team today and let us guide you through your options.
Key takeaways
- Mounjaro (tirzepatide) and Wegovy (semaglutide) are both once-weekly injectable weight loss medications approved for use in the UK.
- In clinical trials, participants without type 2 diabetes taking Mounjaro at the highest dose lost an average of 22.5% of body weight — greater than the approximately 14.9% seen with Wegovy.
- Wegovy works on one hormone receptor (GLP-1), while Mounjaro targets two (GLP-1 and GIP), which may explain the difference in outcomes.
- Both medications are prescription-only and require a full medical assessment before starting treatment.
- Side effect profiles are broadly similar, with nausea and gastrointestinal discomfort most common in the early weeks.
- Neither medication is a standalone solution — both work best alongside a reduced-calorie diet and increased physical activity.
The Differences Between Mounjaro and Wegovy
Mounjaro and Wegovy represent the most advanced injectable weight loss treatments currently available in the UK. Both are administered once a week via a pre-filled pen injector, and both work by mimicking hormones that regulate appetite and blood sugar — but they do so in subtly different ways that have significant implications for their effectiveness.
Wegovy contains semaglutide at a dose of 2.4mg and works by activating the GLP-1 (glucagon-like peptide-1) receptor. This hormone is naturally released after eating and signals to the brain that you are full. By continuously activating this pathway, Wegovy reduces appetite, slows gastric emptying, and helps people eat less without feeling deprived. It was approved for weight management in the UK in 2021 and has since become one of the most widely prescribed weight loss medications in the country.
Mounjaro contains tirzepatide and takes a dual-action approach, activating both the GLP-1 receptor and the GIP (glucose-dependent insulinotropic polypeptide) receptor. GIP is another gut hormone involved in energy balance and fat storage, and the combination of both pathways appears to produce a more powerful effect on appetite suppression and metabolic function. Mounjaro was approved for weight management in the UK in 2023 and has quickly attracted significant attention due to its impressive trial results.
Mounjaro vs Wegovy: Comparing Results
This is the question most people want answered — and the data is striking. In the SURMOUNT-1 trial, participants without type 2 diabetes taking Mounjaro at the highest dose (15mg) lost an average of 22.5% of their body weight over 72 weeks. In the STEP 1 trial, participants taking Wegovy (2.4mg semaglutide) lost an average of approximately 14.9% of their body weight over 68 weeks. On a headline level, that represents a meaningful difference — though it is important to note that both trials used different populations and methodologies, making a direct head-to-head comparison difficult.
A more direct comparison comes from the SURMOUNT-5 trial, which directly compared tirzepatide and semaglutide in adults with obesity, and broadly confirmed that tirzepatide produces greater weight loss across most patient groups. However, averages do not tell the whole story. Some patients respond exceptionally well to Wegovy and achieve results that rival or exceed the Mounjaro average, while others may find Mounjaro’s side effect profile more challenging to manage. This is precisely why personalised medical assessment matters so much.
If you are ready to explore which treatment might be right for you, our team at G.M. Graham Pharmacies is here to help. Get in touch to book a private consultation with our qualified team today and receive a thorough, personalised assessment of your weight management treatment options.
Side Effects of Mounjaro and Wegovy
Both Mounjaro and Wegovy share a broadly similar side effect profile, which is unsurprising given that they both activate the GLP-1 receptor. The most commonly reported side effects include nausea, vomiting, diarrhoea, constipation, and general gastrointestinal discomfort — particularly during the dose escalation phase in the first few months of treatment. In most cases, these side effects are short-lived and improve considerably once the body has had time to adjust to the medication.
Some users of Mounjaro report slightly more pronounced gastrointestinal effects, particularly at higher doses, which may be a consequence of its dual-receptor action. That said, clinical trials suggest that the rate of treatment discontinuation due to side effects is broadly comparable between the two medications. As with all prescription treatments, your prescribing clinician will always discuss your individual risk factors and health history before recommending a starting dose.
Both medications are contraindicated in pregnancy, and caution is advised for individuals with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2 (MEN2). Neither is recommended for people with a personal history of pancreatitis — always disclose this to your prescriber before starting treatment.
See the numbers for yourself. Enter your height and weight into the calculator below and find out how much weight you could potentially lose on Mounjaro or Wegovy based on clinical trial evidence:
Mounjaro vs Wegovy: Which Is Right for You?
The honest answer is that there is no universal winner in the Mounjaro vs Wegovy debate. Mounjaro does produce greater average weight loss in clinical trials, but both medications now have meaningful cardiovascular outcomes data. Wegovy demonstrated a significant reduction in major cardiovascular events in the SELECT trial, making it a well-evidenced choice for patients with established cardiovascular disease. Mounjaro has also shown cardiovascular outcomes data via the SURPASS-CVOT trial, adding to its growing evidence base — the most appropriate choice will depend on your individual health profile and clinical history.
Your prescribing clinician will take into account your weight loss goals, your medical history, any existing conditions or medications, and your personal preferences when making a recommendation. Cost may also be a factor, as prices for both medications can vary between providers. The most important thing is not which medication theoretically produces the best results on average — it is which medication is the most appropriate, safe, and sustainable choice for you as an individual.
Weight loss is never just about the injection. Both Mounjaro and Wegovy work best when combined with meaningful dietary changes, increased physical activity, and ongoing behavioural support. A good weight management programme will address all of these elements alongside the medication itself, giving you the best possible foundation for long-term success. To find out which treatment is the best fit for your needs, contact us to speak to our team at G.M. Graham Pharmacies today.
Frequently Asked Questions
From how the two medications compare to what you can realistically expect, here are the answers to the questions we are asked most often about Mounjaro and Wegovy.
Is Mounjaro stronger than Wegovy?
Clinical trial data suggests that Mounjaro produces greater average weight loss than Wegovy, largely due to its dual-receptor mechanism targeting both GLP-1 and GIP pathways — with participants without type 2 diabetes losing an average of 22.5% of body weight at the highest dose, compared to approximately 14.9% with Wegovy. However, individual responses vary, and “stronger” does not necessarily mean more appropriate for every patient — a personalised medical assessment is always required.
Can I switch from Wegovy to Mounjaro?
It is possible to switch from Wegovy to Mounjaro, but this should only be done under the guidance of a qualified prescriber who can assess whether the switch is clinically appropriate and advise on the correct starting dose. Switching medications without medical guidance could increase the risk of side effects or reduce the effectiveness of your treatment.
Are Mounjaro and Wegovy available on the NHS?
Both medications are available through the NHS in limited circumstances, subject to strict eligibility criteria including BMI thresholds and the presence of weight-related health conditions — and access is currently being phased in gradually through specialist weight management services. For those who do not meet NHS criteria or who face long waiting times, private treatment is a widely used and clinically valid alternative.
How long does it take to see results with Mounjaro or Wegovy?
Most patients begin to notice a reduction in appetite and some early weight loss within the first two to four weeks of treatment, though the most significant results are typically seen over a period of several months as the dose is gradually increased. Both medications are intended for long-term use and produce their greatest results when combined with sustained dietary and lifestyle changes.
What happens when you stop taking Mounjaro or Wegovy?
Research indicates that a significant proportion of patients regain weight after stopping either medication, particularly if the underlying dietary and lifestyle habits have not changed during the treatment period. This is why embedding sustainable behavioural changes alongside the medication is considered an essential part of any effective weight management programme.
Do Mounjaro and Wegovy cause muscle loss?
As with any significant calorie deficit, some loss of lean muscle mass alongside fat loss is possible when taking either medication. To minimise this, clinicians typically recommend ensuring adequate protein intake and incorporating resistance exercise into your routine during treatment.
Mounjaro vs Wegovy: Making the Right Choice for You
When it comes to Mounjaro vs Wegovy, the evidence is clear that both are highly effective tools for weight loss — and that Mounjaro currently holds the edge in terms of average results from clinical trials, particularly in patients without type 2 diabetes. But the numbers only tell part of the story. The right medication is the one that is safe, suitable, and sustainable for you as an individual, taking into account your full health picture, cardiovascular history, and long-term goals.
At G.M. Graham Pharmacies in Essex, we are here to cut through the noise and help you make an informed, confident decision about your weight management journey. Every weight loss journey is different, and our experienced team is here to listen, advise, and guide you through your options whether you are just starting out or reassessing a treatment that is no longer working for you. Take the first step today and book your private consultation with us.
Disclaimer: The information provided in this blog post is intended for general informational purposes only and does not constitute medical advice. Mounjaro and Wegovy are prescription-only medications and must only be used under the supervision of a qualified medical professional. Individual results, suitability, and risks vary — always speak to a pharmacist, GP, or specialist before starting, stopping, or changing any weight management treatment.
