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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Is Mounjaro Going Up? Mounjaro vs Wegovy Compared
If you're asking whether Mounjaro is becoming more popular or gaining ground compared to Wegovy, the answer is yes—in the UK, both medications are increasingly prescribed for weight management, but they work differently. This guide compares Mounjaro (tirzepatide) and Wegovy (semaglutide) side by side, covering mechanism, clinical trial data, eligibility, and what each medication means for your personal situation. Both are prescription-only and require a clinical assessment from a licensed prescriber before either can be recommended to you.
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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 natural hormone pathways simultaneously. This dual mechanism may help regulate appetite more effectively by acting on both glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) pathways.
Wegovy (semaglutide) is a GLP-1 receptor agonist only—it activates the GLP-1 pathway alone. This single-action approach has been used for many years and has a well-established safety profile.
In the SURMOUNT clinical trial, Mounjaro achieved average weight loss of approximately 15–21% body weight depending on dose. In the STEP trial, Wegovy achieved average weight loss of approximately 14.9% body weight. Both are given as once-weekly injections using a KwikPen device. Individual results vary significantly, and both require a reduced-calorie diet and increased physical activity for best results.
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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.
Eligibility, Suitability, and Your Next Steps
Both Mounjaro and Wegovy have the same UK eligibility criteria: a BMI of 30 or above, or 27–29.9 with at least one weight-related health condition (such as type 2 diabetes, prediabetes, high blood pressure, or cardiovascular disease). South Asian, Chinese, Black African, and Black Caribbean adults may be eligible at lower BMI thresholds due to higher cardiovascular risk at lower weights.
Neither medication is suitable for pregnant women, those under 18, or people with certain allergies or medical conditions. Your prescriber will assess your individual health during a clinical consultation. Both require an NHS referral to specialist weight management services or can be prescribed privately through a UK-licensed prescriber following an online consultation. The choice between them depends on your health profile and prescriber recommendation—there is no universally "better" option.
- 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 Mounjaro may result in slightly higher average weight loss (15–21% vs 14.9%), but individual results vary considerably. Both medications are effective. The "best" choice depends on your health profile and what your prescriber recommends after clinical assessment.
What's the difference between GLP-1 and GIP+GLP-1?
GLP-1 alone (Wegovy) activates one appetite-regulating pathway. Mounjaro's dual GIP+GLP-1 mechanism activates two pathways simultaneously, which may enhance appetite suppression. Both approaches have clinical evidence; the dual mechanism is newer in UK weight management.
Can I switch from Wegovy to Mounjaro or vice versa?
Switching between medications should only be done under prescriber guidance. There is no official conversion chart—your prescriber will determine the appropriate starting dose for whichever medication is recommended.
How much do Mounjaro and Wegovy cost in the UK?
NHS access is through specialist weight management services and varies by region. Privately, both cost approximately £129–£320 per month depending on dose and provider. Always use a GPhC-registered pharmacy and UK-licensed prescriber.
Which medication is right for me?
Your prescriber will recommend the most suitable medication based on your health history, BMI, weight-related conditions, allergies, and individual circumstances. Use our GLP-1 weight loss calculator to estimate potential outcomes with either medication, then discuss with your GP or prescriber.
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.