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 Owns and Manufactures Mounjaro?
Mounjaro (tirzepatide) is owned and manufactured by Eli Lilly and Company, a multinational pharmaceutical corporation. Eli Lilly developed tirzepatide as a dual GIP and GLP-1 receptor agonist specifically for weight management. The medication is available as a prescription-only injection in the UK under the brand name Mounjaro, delivered via the KwikPen device. It's important to note that Mounjaro is distinct from other weight loss medications — its dual mechanism sets it apart from single-action GLP-1 agonists like Wegovy (semaglutide), also available in the UK.
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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.
Eli Lilly and Tirzepatide Development
Eli Lilly and Company is a major American pharmaceutical manufacturer headquartered in Indianapolis, Indiana. The company has been operating since 1876 and is one of the world's largest pharmaceutical firms. Eli Lilly invested significantly in developing tirzepatide over many years of clinical research and trials, culminating in the SURMOUNT-1 trial, which demonstrated that Mounjaro may help participants lose an average of 15–21% of body weight when used alongside a reduced-calorie diet and increased physical activity. Results vary significantly between individuals.
In the UK, Mounjaro is subject to additional MHRA monitoring (indicated by a Black Triangle ▼ symbol) and is available exclusively as a prescription-only medicine. This means you cannot purchase it without a prescription from a UK-licensed prescriber following a clinical assessment. Your GP can refer you to specialist NHS weight management services, or you can access private prescribing through a GPhC-registered online pharmacy.
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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.
How Mounjaro Differs From Other Weight Management Medications
Mounjaro's unique dual mechanism — activating both GIP and GLP-1 receptor pathways — distinguishes it from other licensed weight loss injections in the UK. Wegovy (semaglutide) and Saxenda (liraglutide) are single GLP-1 agonists. This dual action may contribute to Mounjaro's effectiveness, though individual responses vary considerably. Mounjaro is administered once weekly via the KwikPen, starting at 2.5 mg and titrating up to a maximum of 15 mg over several weeks. Like all weight loss medications, Mounjaro is prescribed based on individual eligibility criteria — typically a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions. Use our GLP-1 weight loss calculator to explore potential outcomes at different doses.
- 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 the same company as Ozempic?
No. Mounjaro (tirzepatide) is manufactured by Eli Lilly. Ozempic (semaglutide) is made by Novo Nordisk. Both are prescription medications, but Ozempic is licensed for type 2 diabetes, not weight management. Wegovy (also semaglutide, also by Novo Nordisk) is the licensed weight management version in the UK.
Can I buy Mounjaro without a prescription in the UK?
No. Mounjaro is prescription-only in the UK. You must obtain a prescription from a licensed prescriber following a clinical assessment. This can be through NHS specialist services or a private online prescriber registered with the GPhC. Check eligibility using our free BMI calculator above.
How long has Eli Lilly been developing Mounjaro?
Eli Lilly conducted years of research and clinical trials before Mounjaro's approval. The SURMOUNT-1 trial (published 2022) demonstrated efficacy and safety. Mounjaro became available in the UK in 2023 for weight management in eligible adults.
What does the Black Triangle symbol on Mounjaro mean?
The Black Triangle (▼) indicates that Mounjaro is subject to additional MHRA monitoring in the UK. This is standard for newer medications and means healthcare professionals report safety data closely. It does not mean the medication is unsafe — it ensures careful ongoing safety surveillance.
Is Mounjaro available through the NHS in the UK?
Mounjaro is available through NHS specialist tier 3 weight management services in some areas, though availability and waiting lists vary significantly by region and ICB. Private access is available through GPhC-registered online pharmacies. Your GP can discuss which option is suitable for you.
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.