The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
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Mounjaro Price vs Wegovy — What's the Difference?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight loss injections available in the UK, but they work differently and have different pricing structures. Understanding the costs, mechanisms, and clinical evidence for each can help you have an informed conversation with your prescriber about which option might be suitable for you. This guide compares both medications factually so you can understand the key differences beyond price alone.
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Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
How Mounjaro and Wegovy Work — Clinical Trial Evidence
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways simultaneously. In the SURMOUNT-1 clinical trial, participants taking Mounjaro 15 mg achieved an average weight loss of approximately 20.9% of body weight over 72 weeks, alongside reduced-calorie diet and increased physical activity. The 10 mg dose showed average weight loss of around 19.5%.
Wegovy (semaglutide) is a GLP-1 receptor agonist only, activating a single hormone pathway. In the STEP-1 clinical trial, participants taking Wegovy 2.4 mg achieved an average weight loss of approximately 14.9% of body weight over 68 weeks with the same lifestyle support. These are clinical averages — individual results vary significantly, and weight loss is not assured for any individual.
- Mounjaro: dual mechanism (GIP + GLP-1)
- Wegovy: single mechanism (GLP-1 only)
- Both require clinical assessment before prescription
- Both are used alongside dietary changes and physical activity
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How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
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UK Pricing, Doses, and Suitability — Your Prescriber Decides
Mounjaro KwikPen pricing in the UK ranges from approximately £129–£320 per month depending on dose, with doses escalating from 2.5 mg up to a maximum of 15 mg once weekly. Wegovy pricing similarly ranges from approximately £129–£300 per month for doses escalating from 0.25 mg to 2.4 mg once weekly. NHS availability varies significantly by region through specialist tier 3/4 weight management services. Private prescribing through UK-licensed prescribers offers faster access without NHS waiting lists. Your GP or prescriber will assess whether either medication suits your individual health circumstances, medical history, and eligibility based on BMI and weight-related health conditions. Factors beyond price — including mechanism of action, side effect profile, and personal health context — all influence which option is appropriate for you.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
Is Mounjaro more expensive than Wegovy in the UK?
Pricing is broadly similar, ranging £129–£320 monthly depending on dose and provider. Costs vary between private prescribers and NHS services. Your final cost depends on which dose you're prescribed, not the medication name. Ask your prescriber for current pricing with your chosen provider.
Which medication causes more weight loss — Mounjaro or Wegovy?
Clinical trials showed Mounjaro averaged clinically studied weight loss and Wegovy averaged 14.9%. However, individual results vary significantly. Some people respond better to one mechanism than the other. Your prescriber will help determine which is suitable based on your health profile, not trial averages.
Can I switch from Mounjaro to Wegovy or vice versa?
Switching between medications is possible but must be managed by your prescriber. There is no official established conversion dose — approximate equivalences exist but vary by individual. Never switch without guidance from your prescriber.
Why would my prescriber choose one over the other?
Your prescriber considers your medical history, other medications, side effect tolerance, BMI, weight-related health conditions, and individual response to treatment. The dual mechanism of Mounjaro may suit some people better; the single GLP-1 mechanism of Wegovy may suit others. Both require clinical assessment.
How can I work out my potential weight loss with either medication?
Use our free GLP-1 weight loss calculator to estimate potential outcomes at different doses. This gives you a starting point for conversation with your prescriber. Remember that individual results vary, and these are projections based on clinical trial averages, not assures.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.