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 Click and Collect vs Wegovy: What's the Difference?
If you're comparing Mounjaro and Wegovy for weight management in the UK, understanding how they work and their clinical evidence is essential. Both are prescription-only GLP-1-based injections available through UK prescribers, but they have key differences in mechanism, dosing, and trial outcomes. This guide explains the factual differences to help you understand what your prescriber might recommend based on your individual health needs. Use our free BMI calculator above to check your starting point, and our GLP-1 weight loss calculator to explore potential outcomes with either medication.
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Calculate Your BMI Instantly
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.
Clinical Evidence and How They Work
The key difference between Mounjaro (tirzepatide) and Wegovy (semaglutide) lies in their mechanism. Mounjaro is a dual GIP and GLP-1 receptor agonist, activating two natural hormone pathways, whereas Wegovy is a GLP-1 agonist only. This dual action may contribute to different weight loss outcomes.
Clinical trial data shows: SURMOUNT-1 (Mounjaro) demonstrated average weight loss of approximately 15–21% of body weight at maximum dose over 72 weeks, whilst STEP-1 (Wegovy) showed approximately 14.9% at 68 weeks on the highest dose. Individual results vary significantly. Both trials were conducted alongside reduced-calorie diet and increased physical activity — neither medication works alone without lifestyle changes.
- Mounjaro: dual mechanism, once-weekly 2.5–15 mg dosing
- Wegovy: single mechanism, once-weekly 0.25–2.4 mg dosing
- Both require minimum 4 weeks between dose increases
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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
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Which Is Right for You?
Both Mounjaro and Wegovy are prescription-only medicines available in the UK following a clinical assessment. Your prescriber will consider your medical history, current medications, weight-related health conditions, and individual factors when deciding which is appropriate. There is no universal "better" option — suitability is individual.
Access routes: Both are available through NHS specialist tier 3 weight management services (with regional variation) and through private online prescribing services following assessment by a UK-licensed prescriber. Side effects are similar for both medications (nausea, diarrhoea, constipation, stomach pain most common). Your GP can discuss which pathway suits your circumstances and help you access the right support.
- 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 show slightly higher average weight loss with Mounjaro (15–21% vs 14.9% with Wegovy), but individual results vary greatly. "More effective" differs between people. Your prescriber will recommend based on your health profile, not trial averages alone.
Can I switch from Wegovy to Mounjaro on the NHS?
Switching between medications on the NHS requires prescriber approval through your specialist weight management service. There is no established official conversion dose. Any switch must be clinically managed. Discuss with your specialist if you're considering a change.
What's the difference between GLP-1 and GIP/GLP-1?
Wegovy activates GLP-1 (one hormone pathway). Mounjaro activates both GIP and GLP-1 (two pathways). The dual action may influence how appetite and fullness signals work, potentially contributing to different outcomes, though both reduce appetite effectively.
How do I access Mounjaro or Wegovy in the UK?
Both are available through NHS referral to specialist tier 3 services and through private online prescribing following clinical assessment. NHS access varies by region and availability. Private access is typically faster but involves cost. Your GP can advise on both routes.
Are the side effects the same for both medications?
Side effects are broadly similar — nausea, diarrhoea, vomiting, constipation, and stomach pain are most common with both. Severity and duration vary individually. Always review the Patient Information Leaflet with your prescriber before starting either medication.
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.