The UK's most complete GLP-1 guide
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- 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 vs Wegovy: UK Pricing and Comparison
Mounjaro and Wegovy are both prescription weight loss injections available in the UK, but they work differently and have different pricing structures. This guide compares the two medications side-by-side, including mechanism, clinical trial results, and what you need to know about accessing them through NHS or private prescribing. Both require a clinical assessment before prescription — individual suitability depends on your health profile and prescriber recommendation.
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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 Differently
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways in the body. This dual mechanism may help regulate appetite and food intake more comprehensively than single-pathway medications.
Wegovy (semaglutide) is a GLP-1 receptor agonist only, activating a single hormone pathway. Both medications slow gastric emptying and support feeling fuller after meals, but they work through slightly different biological mechanisms.
Clinical trial data shows both medications can support weight loss when used alongside a reduced-calorie diet and increased physical activity. In the SURMOUNT-1 trial, Mounjaro at 15 mg showed average weight loss of around 20.9% of body weight. In the STEP-1 trial, Wegovy at 2.4 mg showed average weight loss of approximately 14.9%. Important: individual results vary significantly, and these are clinical averages, not assured outcomes. Our GLP-1 weight loss calculator can help you understand potential projection ranges with different doses.
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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, Eligibility, and Access Routes
Private prescribing costs in the UK typically range from £129–£320 per month depending on dose and provider, covering the KwikPen device and pharmacy dispensing. Mounjaro starts at 2.5 mg and titrates up to 15 mg maximum. Wegovy starts at 0.25 mg and reaches 2.4 mg maximum — different dosing schedules mean different cost trajectories.
NHS access is available through specialist tier 3/4 weight management services, but availability and waiting times vary significantly by region (ICB). You'll need a referral from your GP. Both medications require ongoing clinical assessment and monitoring.
Eligibility for both is similar: BMI 30 or above, or BMI 27–29.9 with weight-related health conditions (type 2 diabetes, hypertension, dyslipidaemia, sleep apnoea, or cardiovascular disease). For South Asian, Chinese, Black African, or Black Caribbean adults, lower thresholds may apply due to higher health risks at lower BMI levels. A prescriber will assess individual suitability — one medication may be more appropriate than the other based on your medical history, current medications, and health goals.
- 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 effective than Wegovy?
Clinical trials showed Mounjaro produced slightly higher average weight loss (20.9% vs 14.9%), but both are effective. Individual results vary significantly based on genetics, diet, exercise, and how you respond to the medication. Your prescriber will help determine which is more suitable for you personally.
Why is Mounjaro a tirzepatide kwikpen and Wegovy a different device?
Mounjaro uses the KwikPen pre-filled auto-injector device from Eli Lilly. Wegovy uses Novo Nordisk's pre-filled pen. Both are designed for once-weekly self-injection. The device choice doesn't affect effectiveness — it's manufacturer-specific.
Can I switch from Wegovy to Mounjaro on the NHS or privately?
Yes, but switching requires a prescriber's assessment and approval. There's no official conversion chart — approximate equivalence exists (Wegovy 2.4 mg ≈ Mounjaro 10 mg), but any switch must be managed clinically. Your prescriber will guide the transition and monitor your response.
What is tirzepatide and how is it different from semaglutide?
Tirzepatide (Mounjaro) activates both GIP and GLP-1 receptors (dual action). Semaglutide (Wegovy) activates GLP-1 only (single action). The dual mechanism of tirzepatide may support slightly greater appetite suppression, though both support sustainable weight loss alongside lifestyle changes.
How do I check if I'm eligible for Mounjaro or Wegovy in the UK?
Use our free BMI calculator above to check your starting point. Adults with BMI 30+ or 27–29.9 with weight-related conditions may be eligible. Contact your GP for NHS referral to specialist weight management services, or arrange a private online consultation with a UK-licensed prescriber for private access.
Ready to take control of your weight loss journey?
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