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 Prices and Key Differences
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight loss injections available in the UK, but they work differently and have different costs. Understanding the differences in mechanism, dosing, trial results, and UK pricing can help you and your prescriber decide which might be more suitable for you. This guide compares both medications factually so you can have an informed discussion with your GP or prescriber about your options.
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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 — And Why It Matters
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — meaning it activates two natural hormone pathways in the body. This dual mechanism may help regulate appetite and support faster satiety across different phases of eating.
Wegovy (semaglutide) is a GLP-1 receptor agonist only — activating a single hormone pathway. Both are once-weekly injections, but they work through different biological mechanisms.
In clinical trials, Mounjaro showed an average weight loss of approximately 15–21% of body weight (SURMOUNT-1 trial), while Wegovy showed approximately 15% average weight loss (STEP-1 trial) — though individual results vary significantly. The dual mechanism of Mounjaro may account for differences in weight loss outcomes, but which medication suits you depends on your personal health, medical history, and prescriber assessment, not trial averages alone.
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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 and Practical Access Information
Mounjaro and Wegovy prices in the UK vary by dose and provider. Private online prescribing typically costs between £129–£320 per month depending on the dose you're prescribed. NHS access is available through specialist tier 3 weight management services (referral required from your GP), though availability and waiting times vary significantly by region.
Mounjaro comes in doses from 2.5 mg up to 15 mg weekly. Wegovy comes in doses from 0.25 mg up to 2.4 mg weekly. Your prescriber will assess which dose — and which medication — is appropriate based on your individual health profile, not price. Use our free GLP-1 weight loss calculator to understand potential outcomes at different doses alongside your clinical assessment.
- 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.
What's the main difference between Mounjaro and Wegovy?
Mounjaro is a dual GIP+GLP-1 agonist; Wegovy is GLP-1 only. Both are once-weekly injections for weight management. Mounjaro showed slightly higher average weight loss in trials (15–21% vs 15%), but individual results vary. Your prescriber will recommend the most suitable option for you.
How much do Mounjaro and Wegovy cost in the UK?
Private prescribing costs typically range from £129–£320 per month depending on dose. NHS access is available through specialist services (referral required). Costs vary by provider and dose. Always ask your prescriber or pharmacy for current pricing.
Can I switch from Wegovy to Mounjaro or vice versa?
Switching between medications is possible but must be managed by your prescriber. Approximate dose equivalences exist (5mg Mounjaro ≈ 0.5mg Wegovy), but there is no official conversion chart. Your prescriber will manage any switch safely.
Which weight loss injection is better — Mounjaro or Wegovy?
Neither is universally "better" — suitability depends on your individual health, medical history, and how you respond. Both require prescription and clinical assessment. Your GP or prescriber will recommend the most appropriate option for you based on your personal circumstances.
Are Mounjaro and Wegovy available on the NHS?
Yes, both are available through NHS specialist weight management services. Access requires referral from your GP to a tier 3 service. Availability and waiting times vary by region (ICB). Private online prescribing is also available without NHS referral.
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.