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
Free tracker included with every download this week
Who Makes Mounjaro and How It Compares to Wegovy
Mounjaro (tirzepatide) is manufactured by Eli Lilly and Company, a major global pharmaceutical manufacturer. Wegovy (semaglutide) is made by Novo Nordisk. Both are prescription-only weight management injections licensed in the UK, but they work slightly differently and come from different companies. Understanding the differences between these two medications can help you and your GP or prescriber decide which might be more suitable for you. Both require a clinical assessment before prescription, and individual results vary significantly. Use our free BMI calculator and GLP-1 weight loss calculator to explore your potential eligibility and estimated 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.
Manufacturers, Mechanisms, and Trial Data Comparison
Mounjaro (tirzepatide) is manufactured by Eli Lilly and Company, a major US-based pharmaceutical manufacturer. Wegovy (semaglutide) is made by Novo Nordisk, a Danish pharmaceutical company. The key difference is mechanism: Mounjaro is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways simultaneously. Wegovy is a GLP-1 receptor agonist only, activating one pathway. In clinical trials, Mounjaro showed average weight loss of approximately 20.9% at the maximum 15 mg dose (SURMOUNT-1 trial, 72 weeks), while Wegovy showed approximately 14.9% average weight loss at maximum 2.4 mg dose (STEP-1 trial, 68 weeks). However, these are trial averages alongside diet and exercise — individual results vary considerably, and a lower Mounjaro dose may work well for some people.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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 — NHS Eligibility and Prescriber Guidance
Both Mounjaro and Wegovy are prescribed based on the same NHS eligibility criteria: a BMI of 30 or above, or 27–29.9 with weight-related health conditions (such as type 2 diabetes, high blood pressure, or cardiovascular disease). A prescriber will assess you individually to determine which is more suitable based on your medical history, other medications, and personal preferences. Neither medication is "better" overall — suitability is individual. Access in the UK is through NHS specialist weight management services (tier 3) or private online prescribing following a clinical consultation. Your GP or licensed prescriber can advise which option may be most appropriate for your circumstances.
- 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 made by Eli Lilly or Novo Nordisk?
Mounjaro (tirzepatide) is made by Eli Lilly and Company. Novo Nordisk makes Wegovy (semaglutide). Both are prescription-only weight management medications licensed in the UK, but from different manufacturers with slightly different mechanisms of action.
What is the main difference between Mounjaro and Wegovy?
Mounjaro is a dual GIP and GLP-1 receptor agonist (activates two hormone pathways), while Wegovy is a GLP-1 receptor agonist only (one pathway). This may explain why clinical trials showed Mounjaro with slightly higher average weight loss, though individual results vary significantly.
Which showed better results in clinical trials — Mounjaro or Wegovy?
Mounjaro showed average weight loss of approximately 20.9% (SURMOUNT trial at 15 mg), while Wegovy showed approximately 14.9% (STEP trial at 2.4 mg). However, these are trial averages. Individual results depend on dose, adherence, diet, exercise, and personal metabolism — both medications can be effective.
Can my GP prescribe either Mounjaro or Wegovy on the NHS?
Access is through NHS specialist tier 3 weight management services, not standard GP prescription. NHS availability varies by region. Alternatively, both are available privately through UK-licensed online prescribers following a clinical assessment, typically without NHS referral.
How do I know which medication is right for me?
A prescriber will assess your individual circumstances, including medical history, other medications, BMI, and weight-related health conditions. Both require clinical assessment. Try our free GLP-1 weight loss calculator to explore potential outcomes, and discuss eligibility with your GP or a licensed 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.