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 Manufactures Mounjaro and How It's Used in the UK
Mounjaro (tirzepatide) is manufactured by Eli Lilly and Company, a major pharmaceutical manufacturer. In the UK, Mounjaro is a prescription-only medicine approved by the MHRA (Medicines and Healthcare products Regulatory Authority) for weight management in adults. NICE has approved tirzepatide for use within NHS specialist weight management services. Understanding who manufactures this medication, how it's regulated, and where you can access it helps you make informed decisions about weight management options available in the UK.
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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.
Eli Lilly Manufacturing and UK Regulatory Approval
Eli Lilly and Company is a global pharmaceutical manufacturer headquartered in the United States. The company manufactures Mounjaro as a pre-filled KwikPen injection device containing tirzepatide. In the UK, Mounjaro is subject to additional MHRA monitoring (indicated by a Black Triangle (▼) status), which means new safety data is actively reviewed.
The MHRA approved Mounjaro in June 2023 for weight management in adults with a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. NICE guidance (NG220) recommends tirzepatide as a treatment option within specialist tier 3 weight management services. Each KwikPen contains four weekly doses and is supplied in doses ranging from 2.5 mg to 15 mg. The medication must be stored in a refrigerator at 2–8°C before first use.
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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.
NHS Access and Private Prescribing Routes
In the UK, Mounjaro is available through two routes. NHS access is via referral to a specialist tier 3 or tier 4 weight management service, typically arranged by your GP. NICE guidance supports this pathway for eligible adults, though availability and waiting times vary significantly by region (ICB). Private access is available through GPhC-registered online pharmacies following a clinical assessment from a UK-licensed prescriber—this route does not require NHS referral.
Eligibility criteria are the same regardless of route: BMI of 30 or above, or 27–29.9 with weight-related health conditions. Lower BMI thresholds may apply for people of South Asian, Chinese, Black African, or Black Caribbean heritage. Your prescriber will assess whether Mounjaro is suitable for your individual health circumstances. Clinical trials showed participants on Mounjaro lost an average of 15–21% of their body weight, though individual results vary significantly.
- 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 manufactured in the UK?
No, Mounjaro is manufactured by Eli Lilly and Company globally. However, it is licensed and approved for use in the UK by the MHRA and can be prescribed through NHS services or private prescribers following clinical assessment.
What does the Black Triangle status mean on Mounjaro?
The Black Triangle (▼) indicates that Mounjaro is subject to additional MHRA monitoring. This is standard for newer medications and means safety data is actively reviewed. It does not mean the medication is unsafe—it reflects that it's relatively new and requires close pharmacovigilance.
How do I access Mounjaro on the NHS?
Ask your GP for a referral to your local specialist weight management service (tier 3 or tier 4). NICE recommends tirzepatide for eligible adults, though availability varies by region. You can also access Mounjaro privately through GPhC-registered online pharmacies without NHS referral.
What is the difference between Mounjaro and Wegovy in the UK?
Both are prescription-only weight management injections licensed in the UK. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist manufactured by Eli Lilly. Wegovy (semaglutide) is a GLP-1 receptor agonist manufactured by Novo Nordisk. Both are used alongside diet and physical activity changes.
What is tirzepatide exactly?
Tirzepatide is the active ingredient in Mounjaro. It's a synthetic medication that activates two natural hormone pathways (GIP and GLP-1) to help regulate appetite, support feeling fuller after meals, and aid weight management. It's administered as a once-weekly injection via the Mounjaro KwikPen.
Ready to take control of your weight loss journey?
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