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 vs Wegovy — UK Price and Access Comparison
Mounjaro and Wegovy are both prescription-only GLP-1 weight loss injections available in the UK, but they differ in price, mechanism, and trial outcomes. Understanding the cost differences and which medication may be suitable for you requires knowledge of how these medications work, their clinical evidence, and current UK pricing. This guide compares both options to help you make an informed conversation with your GP or prescriber.
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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 Differ — Mechanism and Trial Evidence
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways simultaneously. Clinical trials (SURMOUNT-1) showed average weight loss of approximately 15–21% of body weight over 72 weeks, depending on dose, when used alongside a reduced-calorie diet and increased physical activity. Doses range from 2.5 mg to 15 mg once weekly.
Wegovy (semaglutide) is a GLP-1-only receptor agonist. The STEP-1 clinical trial showed average weight loss of approximately 14.9% of body weight at 68 weeks on the maximum 2.4 mg dose, again with lifestyle changes. Individual results vary significantly between people.
The key difference is mechanism: Mounjaro's dual action on GIP and GLP-1 may account for slightly higher average weight loss in trials, though this does not assures better outcomes for any individual. Your prescriber will assess which is more appropriate based on your health profile, not just trial averages.
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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, NHS Access, and Private Availability
Private Mounjaro pricing typically ranges from £150–£320 per month depending on dose and provider. Wegovy pricing is similar, generally £130–£300 per month. Prices vary between GPhC-registered pharmacies, so comparison across providers is recommended. NHS access is more limited: both medications are available through NHS specialist tier 3 weight management services, but eligibility criteria and waiting times vary significantly by region. Many areas have lengthy waiting lists. Most people accessing these medications privately do so through online prescribing following a clinical assessment with a UK-licensed prescriber. Regardless of route, prescription is required—neither medication is available over the counter.
Eligibility for both Mounjaro and Wegovy in the UK requires a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with weight-related health conditions such as type 2 diabetes, hypertension, or cardiovascular disease. South Asian, Chinese, Black African, and Black Caribbean adults may have access at slightly lower BMI thresholds. A licensed prescriber will assess your individual circumstances during a clinical consultation. Use our free GLP-1 weight loss calculator to explore potential outcomes, and our BMI calculator to check your starting point—both tools can support your conversation with your prescriber about which medication may be suitable.
- 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?
Prices are broadly comparable in private UK pharmacies. Both range from approximately £130–£320 per month depending on dose. Specific pricing varies between providers, so shopping around is recommended. NHS access depends on your region and local commissioning policies.
Which medication causes more weight loss — Mounjaro or Wegovy?
Clinical trials show Mounjaro achieved slightly higher average weight loss (15–21%) versus Wegovy (approximately 14.9%), but these are averages and individual results vary significantly. Which works better for you depends on your personal response, health profile, and prescriber assessment—not trial data alone.
Can I switch from Wegovy to Mounjaro on the NHS?
NHS switching between medications is possible but depends on your regional weight management service and clinical circumstances. You would need to discuss this with your NHS prescriber. Private sector switches may be more straightforward with a licensed prescriber.
Do I need a prescription for Mounjaro or Wegovy?
Yes, both are prescription-only medicines in the UK. You cannot buy them over the counter. A UK-licensed prescriber must assess your eligibility and issue a prescription. This applies whether you access through NHS services or private online prescribing.
How do I know which medication is right for me?
Your prescriber will assess your health history, current medications, BMI, and weight-related conditions to recommend the most appropriate option. Neither medication is universally "better"—suitability is individual. Be honest with your prescriber about your health and lifestyle to get the best recommendation.
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.