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 Cost Comparison
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight loss injections available in the UK, but they differ in mechanism, dosing, cost, and clinical evidence. This guide compares both medications factually so you can understand what your prescriber may recommend. Remember that eligibility and suitability are assessed individually by a licensed prescriber following a clinical assessment — neither medication is right for everyone. Use our free BMI calculator above to check your starting point, then explore the differences below.
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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 Trials
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways to help regulate appetite and blood sugar. Clinical trials (SURMOUNT-1) showed average weight loss of approximately 15–21% body weight over 72 weeks, depending on dose. The KwikPen is injected once weekly, with doses ranging from 2.5 mg to 15 mg.
Wegovy (semaglutide) is a GLP-1-only receptor agonist — it activates one hormone pathway. Clinical trials (STEP-1) showed average weight loss of approximately 14.9% body weight over 68 weeks. The auto-injection pen is also once weekly, with doses ranging from 0.25 mg to 2.4 mg.
- Mounjaro: dual mechanism, potentially stronger appetite suppression
- Wegovy: single mechanism, established longer track record
- Both: prescription-only, require clinical assessment, alongside diet and exercise
- Individual results vary significantly
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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.
Free Weight Loss Tools & Guides
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UK Pricing, Availability, and Prescriber Considerations
Private Mounjaro costs typically range from £129–£320 per month depending on dose, with prices varying by provider. Wegovy private pricing is similarly positioned. NHS access is limited and regional — both medications are available through tier 3 specialist weight management services, but waiting lists can be substantial. Your GP can refer you to your local specialist service, though availability varies significantly by ICB area.
A prescriber will assess your individual eligibility based on BMI, health conditions, and personal factors. Neither medication is "better" — suitability depends on your health profile, contraindications, and response to treatment. If you're exploring options, use our GLP-1 weight loss calculator to estimate potential outcomes, then discuss both medications with your prescriber.
- 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 uses a dual GIP+GLP-1 mechanism while Wegovy uses GLP-1 only. This means Mounjaro may have a stronger appetite-suppressing effect, but both work as weight loss injections. Clinical trial data shows similar overall weight loss — individual results vary depending on dose and response.
Is Mounjaro cheaper than Wegovy in the UK?
Private pricing is broadly comparable, typically £129–£320 per month depending on dose and provider. NHS access is limited for both and varies by region. Your prescriber will determine which is available and appropriate for you based on clinical assessment, not cost alone.
Which medication should I choose — Mounjaro or Wegovy?
A licensed prescriber will assess your individual health, contraindications, and suitability. Neither medication is universally "better" — the right choice depends on your medical history, how you respond to treatment, and what your specialist recommends following a thorough assessment.
Can I switch from Wegovy to Mounjaro or vice versa?
Any switch between medications must be managed by your prescriber. While approximate dose equivalences exist (roughly 1.7 mg Wegovy ≈ 10 mg Mounjaro), there is no official conversion protocol. Your prescriber will guide the timing and dosing if a switch is clinically appropriate.
Are Mounjaro and Wegovy available on the NHS?
Both are available through NHS tier 3 specialist weight management services, but regional availability is very limited and waiting lists can be long. Your GP can refer you for specialist assessment. Private online prescribing is also available without NHS referral if you meet eligibility criteria.
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.