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 A GLP-1 Injection?
Mounjaro is not technically a GLP-1 medication — it's something different and potentially more powerful. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it works on two hormone pathways instead of one. This dual action is what sets it apart from Wegovy and other GLP-1-only weight loss injections. Understanding how Mounjaro works compared to traditional GLP-1 medications is important if you're considering prescription weight loss treatment in the UK through the NHS or private prescribing services.
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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.
How Mounjaro's Dual Mechanism Works
While Wegovy is a pure GLP-1 receptor agonist, Mounjaro activates two hormone pathways: GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide). Both are natural hormones your gut produces after eating. GLP-1 signals fullness to your brain and slows gastric emptying. GIP also helps regulate appetite and fat utilisation. By targeting both pathways, Mounjaro may help suppress appetite more effectively than single-pathway GLP-1 medications. Clinical trials showed participants using Mounjaro lost an average of 15–21% of their body weight over 72 weeks — similar to or slightly higher than GLP-1-only medications. Use our free GLP-1 weight loss calculator above to explore projected weight loss at different Mounjaro doses. The dual mechanism is why Mounjaro (tirzepatide) may feel different from Wegovy — though 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
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Mounjaro vs GLP-1 Medications in the UK
In the UK, both Mounjaro and GLP-1 medications like Wegovy are prescription-only and require clinical assessment. The NHS may prescribe either through specialist tier 3 weight management services, depending on availability and regional variation. Privately, both are accessible via online clinical assessment from UK-licensed prescribers. Mounjaro comes as a once-weekly KwikPen injection with doses ranging from 2.5 mg to 15 mg. While Mounjaro isn't a GLP-1, it's often grouped with GLP-1 medications because they serve the same purpose: supporting weight loss alongside dietary changes and physical activity. Your GP or prescriber can assess which medication suits your individual health needs. Try our BMI calculator above to check your starting point — eligibility for either medication typically requires a BMI of 30 or above, or 27+ with weight-related health conditions.
- 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 classified as a GLP-1?
No. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — it works on two hormone pathways, not just GLP-1. This dual action may make it more effective for appetite suppression than single-pathway GLP-1 medications like Wegovy, though results vary between individuals.
What's the difference between Mounjaro and Wegovy?
Wegovy is a pure GLP-1 receptor agonist, whilst Mounjaro activates both GIP and GLP-1 pathways. Clinical trials showed similar average weight loss (15–21% for Mounjaro vs ~15% for Wegovy), but Mounjaro's dual mechanism may work differently for some people. Both are prescription-only in the UK.
Can I get Mounjaro on the NHS in the UK?
Mounjaro is available through NHS specialist tier 3 weight management services for adults meeting eligibility criteria (BMI ≥30, or ≥27 with weight-related health conditions). However, NHS availability varies significantly by region. Waiting lists can be lengthy. Private prescribing is an alternative route.
How do I know if Mounjaro is right for me?
Only a UK-licensed prescriber can assess your suitability following a clinical consultation. They'll evaluate your BMI, health conditions, medications, and personal circumstances. You cannot diagnose your own eligibility — always consult your GP or a qualified healthcare professional.
What does Mounjaro cost in the UK?
NHS costs are covered by the health service if prescribed. Private costs typically range from £150–£320 per month depending on dose and provider. Higher doses (10–15 mg) cost more than starting doses (2.5–5 mg). Prices vary between private prescribing services.
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.