If you have been researching weight loss injections, you will almost certainly have come across two names: Mounjaro and Wegovy. Both are prescription medications that have transformed how we approach weight management, and both are now available through community pharmacies in the UK. But they are not the same drug, they do not work in exactly the same way, and one may suit you better than the other.
At Norfolk Street Pharmacy in Stoke-on-Trent, we prescribe both Mounjaro (tirzepatide) and Wegovy (semaglutide) as part of our supervised weight loss programme. In this guide, we break down the real differences so you can have an informed conversation with our pharmacist about which option is right for your body, your health, and your goals.
What Are Mounjaro and Wegovy, and How Do They Work?
Both Mounjaro and Wegovy belong to a class of medications known as GLP-1 receptor agonists. They mimic a natural gut hormone called GLP-1 (glucagon-like peptide-1), which tells your brain you are full after eating. By activating this pathway, both drugs reduce appetite, slow stomach emptying, and help you eat less without the constant battle against hunger.
The key difference lies in their mechanism. Wegovy (semaglutide) targets only the GLP-1 receptor. It was developed by Novo Nordisk and received MHRA approval for weight management in the UK in 2022. It is administered as a once-weekly injection using a pre-filled pen.
Mounjaro (tirzepatide) goes a step further. Developed by Eli Lilly, it targets both the GLP-1 and GIP (glucose-dependent insulinotropic polypeptide) receptors. This dual-action approach means Mounjaro works on two appetite-regulating pathways simultaneously. It is also a once-weekly injection using a pre-filled pen. Mounjaro received MHRA approval for weight management in the UK in late 2024.
In practical terms, both drugs make you feel fuller sooner, reduce cravings, and help you make better food choices naturally. The dual-receptor action of Mounjaro may give it a slight edge in total weight loss for some patients, but individual responses vary significantly.
What Do the Clinical Trials Tell Us About Results?
The clinical evidence for both medications is strong, but the headline numbers do differ. In the SURMOUNT clinical trial programme, patients taking the highest dose of Mounjaro (15mg) lost an average of 22.5% of their body weight over 72 weeks. For a person weighing 100kg, that represents roughly 22.5kg of weight loss.
In the STEP clinical trial programme for Wegovy, patients on the maintenance dose (2.4mg) lost an average of 14.9% of their body weight over 68 weeks. Using the same 100kg example, that works out to around 14.9kg.
These are averages from controlled clinical trials, and your personal results may be higher or lower depending on factors such as your starting weight, diet, physical activity, metabolism, and how consistently you use the medication. Some of our patients at Norfolk Street Pharmacy have exceeded these averages, while others have seen more modest results. Both outcomes are completely normal.
It is also worth noting that Wegovy has longer real-world data behind it, as it has been available for longer. The cardiovascular benefits of semaglutide are well established, with the SELECT trial showing a 20% reduction in major cardiovascular events in overweight adults.
What Are the Side Effects of Each Injection?
Because both medications work on similar pathways, they share many of the same side effects. The most common are gastrointestinal symptoms, particularly in the first few weeks as your body adjusts:
- Nausea — the most frequently reported side effect for both drugs. It is usually mild to moderate and improves over time.
- Vomiting and diarrhoea — more common during dose escalation periods.
- Constipation — some patients experience this instead of diarrhoea.
- Stomach pain or bloating — caused by slower gastric emptying.
- Reduced appetite — this is essentially the intended effect, but some patients find it more pronounced than expected initially.
Both Mounjaro and Wegovy use a gradual dose escalation schedule specifically to minimise these side effects. You start on the lowest dose and increase every four weeks, giving your body time to adjust. Our pharmacists monitor you throughout this process and can adjust the schedule if side effects are troublesome.
Serious side effects are rare for both medications but can include pancreatitis, gallbladder problems, and allergic reactions. Neither drug should be used by anyone with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2. During your initial consultation at Norfolk Street Pharmacy, we review your full medical history to ensure the medication is safe for you.
Who Is Eligible for Weight Loss Injections?
Both Mounjaro and Wegovy are prescription-only medications. To be eligible, you generally need to meet the following criteria:
- A BMI of 30 or above (obese), or
- A BMI of 27 or above (overweight) with at least one weight-related health condition such as type 2 diabetes, high blood pressure, high cholesterol, or obstructive sleep apnoea
- Age 18 or over
- Not pregnant, breastfeeding, or planning to become pregnant within the treatment period
At your initial consultation, our pharmacist will measure your weight, height, and BMI, review your medical history and current medications, and discuss your weight loss goals. If you are suitable for treatment, we will recommend the medication that best fits your clinical profile and preferences.
How Much Do Mounjaro and Wegovy Cost?
Weight loss injections are currently a private service and are not routinely available on the NHS for weight management alone (though both are available on NHS prescription for type 2 diabetes management). Costs vary depending on the dose and supplier, but as a general guide:
- Wegovy typically costs between 150 and 250 per month, depending on the dose level.
- Mounjaro typically costs between 150 and 230 per month, depending on the dose level.
We always discuss costs transparently during your consultation so there are no surprises. We also offer ongoing monitoring and support as part of our weight loss programme, which includes regular weigh-ins, dietary guidance, and dose adjustments.
Which Injection Should You Choose?
There is no single correct answer. The best choice depends on your individual circumstances. Here are some factors that may help guide your decision:
- If maximum weight loss is your priority and you have no contraindications, Mounjaro’s dual-receptor action may offer a slight advantage based on clinical trial data.
- If you have cardiovascular concerns, Wegovy has the strongest evidence for heart health benefits, backed by the SELECT trial.
- If you have tried semaglutide (Wegovy) before and it did not work well for you, switching to Mounjaro may produce different results due to the additional GIP receptor activity.
- If cost is a factor, pricing is similar, but availability can fluctuate. We will advise you on the most cost-effective option at the time of your consultation.
- If you prefer longer-established medications, Wegovy has a longer track record in the UK market.
Ultimately, our pharmacists will help you make this decision based on a thorough clinical assessment. There is no pressure to choose one over the other, and we can switch medications during your treatment if needed.
What Lifestyle Changes Should You Make Alongside the Injections?
Neither Mounjaro nor Wegovy is a magic solution. Both work best when combined with sustainable lifestyle changes. The medications reduce your appetite and make it easier to eat less, but the quality of what you eat still matters.
We recommend focusing on protein-rich meals to maintain muscle mass during weight loss, staying well hydrated (especially given the gastrointestinal side effects), and building regular physical activity into your week. Even 30 minutes of brisk walking five days a week can significantly improve your results and overall health.
Our pharmacists at Norfolk Street Pharmacy provide ongoing healthy living advice as part of your weight loss journey, including practical meal suggestions and activity recommendations tailored to your lifestyle.
Frequently Asked Questions
Can I switch from Wegovy to Mounjaro or vice versa?
Yes. If one medication is not producing the expected results or you are experiencing persistent side effects, we can discuss switching to the alternative. There is usually a short washout period, and you will restart the dose escalation with the new medication.
How long do I need to take weight loss injections?
Clinical guidelines suggest treatment for at least 12 months to achieve meaningful, sustained weight loss. Some patients choose to continue longer. If you stop the medication without having established strong lifestyle habits, there is a risk of weight regain. We work with you to plan a realistic long-term strategy.
Will I feel hungry on these medications?
Most patients report a significant reduction in appetite and food cravings. Some describe it as simply not thinking about food as often. The effect is usually noticeable within the first few weeks of treatment and becomes more pronounced as the dose increases.
Are these injections painful?
Both Mounjaro and Wegovy use very fine needles in pre-filled pens, similar to insulin pens used by diabetic patients. Most people describe the injection as a brief pinch. You inject into the thigh, abdomen, or upper arm once per week, and we will show you exactly how to do it during your first appointment.
Do I need regular check-ups while on treatment?
Yes. We schedule regular reviews, typically monthly at first and then every 8 to 12 weeks once you are on a stable dose. These appointments allow us to track your progress, manage any side effects, and adjust your treatment plan. Monitoring is an essential part of safe, effective weight loss.
If you are ready to take control of your weight and want expert guidance on whether Mounjaro or Wegovy is right for you, visit Norfolk Street Pharmacy at 1-5 Norfolk Street, Stoke-on-Trent, or call us on 01782 27 20 27. You can also book your weight loss consultation online to get started.