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
What Is Mounjaro Called By Its Generic Name?
Mounjaro is the brand name for a prescription-only weight management injection. The generic name—the active ingredient—is tirzepatide (pronounced tir-ZEP-a-tide). In the UK, you may hear healthcare professionals refer to it by either name, and both are correct. Understanding the difference between the brand name and generic name helps you navigate NHS and private prescriptions clearly.
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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.
Generic Name vs Brand Name: What's the Difference?
Brand name: Mounjaro — this is the name manufactured and marketed by Eli Lilly. It's what you'll see on prescriptions and the pre-filled KwikPen device.
Generic name: Tirzepatide — this is the active pharmaceutical ingredient that does the work. On NHS prescriptions and clinical assessments, you may see tirzepatide mentioned instead of Mounjaro.
Both names refer to the exact same medication. Using the generic name tirzepatide can sometimes help with NHS referrals or discussions with your GP, as they may be more familiar with the generic term in clinical settings. The medication comes as the Mounjaro KwikPen—a pre-filled, single-dose injection pen used once weekly.
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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 to Talk About Mounjaro With Your Healthcare Team
When discussing weight management options with your GP or a licensed prescriber, you can use either name confidently. If you're referred to an NHS specialist weight management service, they'll likely use the generic term tirzepatide in their assessments and documentation. For private online consultations, you may see both names used interchangeably on clinical assessment forms.
Use our free BMI calculator above to check your current BMI—this information is essential for any clinical assessment, whether NHS or private. Understanding your BMI helps you and your prescriber determine eligibility and discuss whether tirzepatide (Mounjaro) may be appropriate for your health profile.
- 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 the same as tirzepatide?
Yes, completely. Mounjaro is the brand name; tirzepatide is the generic name for the same active ingredient. Both refer to the identical prescription-only injection manufactured by Eli Lilly for weight management in UK adults.
Will my prescription say Mounjaro or tirzepatide?
Either is possible. NHS prescriptions often use the generic name tirzepatide, while private prescriptions may use the brand name Mounjaro. Both are valid and refer to the same medication delivered via the KwikPen device.
Is there another brand name for tirzepatide in the UK?
No. In the UK, tirzepatide is only marketed under the brand name Mounjaro for weight management. It is not available under any other brand name for weight loss purposes in British healthcare.
How does Mounjaro (tirzepatide) work differently from Wegovy?
Mounjaro is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) is a GLP-1-only agonist. Both are once-weekly injections, but Mounjaro's dual mechanism may offer different weight loss results. Clinical trials showed Mounjaro achieved average weight loss of around 15–21%, though individual results vary significantly.
Do I need a prescription to get Mounjaro (tirzepatide)?
Yes. Mounjaro is prescription-only in the UK and requires a clinical assessment before being prescribed—either through NHS specialist services or a private licensed prescriber. You cannot obtain it without a valid prescription from a UK-licensed healthcare professional.
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.