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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Who Makes Mounjaro and How It Compares to Wegovy
Mounjaro is manufactured by Eli Lilly and Company, a pharmaceutical manufacturer based in the United States. The active ingredient is tirzepatide (pronounced tir-ZEP-a-tide). While Mounjaro is made by Eli Lilly, another popular weight loss injection called Wegovy is made by Novo Nordisk. Both are prescription-only medicines licensed in the UK for weight management in adults, but they work differently and come from different manufacturers. Understanding who makes these medications and how they differ can help you and your GP make an informed decision about which might be suitable for 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.
Mounjaro vs Wegovy — Key Differences by Manufacturer
Mounjaro (tirzepatide) by Eli Lilly works differently from Wegovy because it is a dual GIP and GLP-1 receptor agonist. This means it activates two natural hormone pathways in the body, which may help regulate appetite and support feeling fuller after meals more effectively than single-mechanism medications.
Wegovy (semaglutide) by Novo Nordisk is a GLP-1 receptor agonist only — it activates one hormone pathway. Clinical trial data shows: Mounjaro SURMOUNT-1 trial participants lost an average of 20.9% of body weight at the maximum 15 mg dose over 72 weeks. Wegovy STEP-1 trial participants lost approximately 14.9% of body weight at the 2.4 mg dose over 68 weeks. Both results were achieved alongside a reduced-calorie diet and increased physical activity. Individual results vary significantly, and both medications have similar common side effects including nausea, diarrhoea, and constipation.
Your GP or prescriber will assess which medication — if either — is suitable based on your individual health, medical history, and preferences.
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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.
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How to Access Mounjaro and Wegovy in the UK
Both Mounjaro and Wegovy are prescription-only medicines in the UK, so you cannot buy either without a valid prescription from a UK-licensed prescriber. NHS access: Both medications are available through NHS specialist tier 3 weight management services, though availability varies by region and waiting times can be long. Private access: Both are available through private online prescribing services following an online clinical assessment with a UK-licensed prescriber.
Eligibility typically requires a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Try our free GLP-1 weight loss calculator above to estimate potential outcomes at different doses, or use our BMI calculator to check your starting point.
- 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.
Who manufactures Mounjaro?
Mounjaro (tirzepatide) is manufactured by Eli Lilly and Company, a major pharmaceutical manufacturer. The tirzepatide KwikPen device is produced by Eli Lilly and distributed through licensed UK pharmacies following a valid prescription.
What company makes Wegovy?
Wegovy (semaglutide) is manufactured by Novo Nordisk, a Danish pharmaceutical company. Novo Nordisk also manufactures Ozempic (semaglutide for diabetes), but Wegovy is the specific formulation licensed in the UK for weight management.
Is Mounjaro or Wegovy better?
Neither is "better" — they work differently and suit different individuals. Mounjaro uses dual GIP+GLP-1 mechanism; Wegovy uses GLP-1 only. Clinical trials show Mounjaro achieved slightly higher average weight loss, but individual results vary. Your prescriber will assess which is appropriate for your health situation.
Can I switch between Mounjaro and Wegovy?
Switching between medications must be managed by your prescriber. There is no official NHS conversion chart between them, though approximate dose equivalencies exist based on clinical practice. Any switch requires medical oversight and reassessment.
Which weight loss injection is available on the NHS?
Both Mounjaro and Wegovy are available through NHS specialist weight management services (tier 3), though availability and waiting times vary significantly by region and ICB. Your GP can refer you to your local specialist service to discuss options.
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.