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 Manufactures Mounjaro?
Mounjaro (tirzepatide) is manufactured by Eli Lilly and Company, a major international pharmaceutical manufacturer based in the United States. Mounjaro is a prescription-only, once-weekly injectable medicine approved in the UK for weight management in adults. It's supplied as a pre-filled KwikPen device and works as a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways to help regulate appetite and support weight loss when used alongside a reduced-calorie diet and increased physical activity. Understanding who manufactures your medication and how it works can help you make informed health decisions.
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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.
About Eli Lilly and Mounjaro
Eli Lilly and Company is one of the world's largest pharmaceutical manufacturers, headquartered in Indianapolis, Indiana, USA. The company has been developing medicines for over 150 years and operates across multiple therapeutic areas including endocrinology, oncology, and immunology. Mounjaro represents their dual GIP and GLP-1 innovative for weight management.
In the UK, Mounjaro is subject to additional MHRA monitoring (indicated by a Black Triangle ▼ symbol on the packaging), meaning it requires close safety surveillance post-approval. The tirzepatide KwikPen is manufactured to strict pharmaceutical standards and contains four pre-filled doses of 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, or 15 mg depending on your dose level. Each pen delivers a once-weekly subcutaneous injection.
- Manufactured by Eli Lilly and Company (US-based)
- MHRA-approved for UK use
- Available through NHS specialist services and private prescription
- Pre-filled KwikPen format — four weeks' supply per pen
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.
Mounjaro vs Other Weight Loss Medications
Mounjaro (tirzepatide) differs from other UK-licensed weight loss injections like Wegovy (semaglutide), which is manufactured by Novo Nordisk and contains a single GLP-1 agonist rather than the dual mechanism of Mounjaro. In clinical trials (SURMOUNT-1), Mounjaro helped participants lose an average of 15–21% of body weight, though individual results vary significantly.
If you're considering weight loss treatment, our free GLP-1 weight loss calculator can help you understand potential weight loss ranges at different doses. Your GP or a licensed prescriber can assess which medication, if any, is appropriate for your individual circumstances following a clinical assessment.
- 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 in the USA or the UK?
Mounjaro is manufactured by Eli Lilly and Company, which is based in the United States. However, it is MHRA-approved for use in the UK and is supplied through both NHS specialist weight management services and private prescription channels.
Is Mounjaro the same as Ozempic?
No. Mounjaro (tirzepatide) and Ozempic (semaglutide) are different medications made by different manufacturers. Mounjaro is made by Eli Lilly and works as a dual GIP and GLP-1 agonist. Ozempic is made by Novo Nordisk and is approved for type 2 diabetes, not weight loss. Wegovy (also semaglutide by Novo Nordisk) is the licensed weight loss version.
How do I get a Mounjaro prescription in the UK?
Mounjaro is prescription-only and requires a clinical assessment. You can access it through NHS specialist tier 3 weight management services (via GP referral) or through a private online consultation with a UK-licensed prescriber. Eligibility is based on BMI and health circumstances.
What is the Black Triangle on Mounjaro?
The Black Triangle (▼) symbol indicates that Mounjaro requires additional MHRA monitoring for safety. This is common for newly approved medicines and means side effects should be reported to the Yellow Card scheme. It does not mean the medication is unsafe — only that it's under close surveillance.
How long does a Mounjaro KwikPen last?
Each pre-filled KwikPen contains four weeks' worth of doses (one injection per week). You'll receive a new pen every four weeks when you increase your dose or continue maintenance therapy. Storage is in a refrigerator (2–8°C) when unopened, or at room temperature below 30°C for up to 30 days after first use.
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.