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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What Is Mounjaro? Understanding the Name and Generic Drug
Mounjaro is the brand name for tirzepatide, a prescription-only injection licensed in the UK for weight management in adults. If you've seen "tirzepatide" mentioned and wondered how it relates to Mounjaro, they're the same medication — tirzepatide is the generic (medical) name, while Mounjaro is the brand name given by the manufacturer, Eli Lilly. Understanding this distinction helps when discussing your medication with your GP or healthcare provider. Both terms are used interchangeably in the UK health system.
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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.
How Mounjaro Works — The Tirzepatide Mechanism
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — what makes it different from other weight management injections like Wegovy (semaglutide), which activates only the GLP-1 pathway. Tirzepatide works by mimicking two natural hormones that help regulate appetite and blood sugar control.
When you take Mounjaro:
- The GIP and GLP-1 pathways signal to your brain that you're fuller after eating
- Food moves through your stomach more slowly, extending the feeling of fullness
- Your body's natural appetite regulation improves
- Blood sugar control is supported alongside weight management
In clinical trials (SURMOUNT-1), participants taking tirzepatide lost an average of 15–21% of their body weight over 72 weeks, though individual results vary significantly. Mounjaro is always used alongside a reduced-calorie diet and increased physical activity — it's not a standalone treatment.
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 Injections — Key Differences
The main difference between Mounjaro (tirzepatide) and Wegovy (semaglutide) is the mechanism: Mounjaro targets two hormone pathways (GIP + GLP-1), while Wegovy targets only GLP-1. This dual action may help some people achieve greater weight loss, though results vary between individuals.
There's also Saxenda (liraglutide), which is a daily injection rather than once-weekly like Mounjaro and Wegovy. In the UK, all three are prescription-only medicines requiring a clinical assessment before prescribing.
Use our free GLP-1 weight loss calculator to explore potential weight loss projections at different doses, and try the BMI calculator to assess your current starting point before discussing treatment with your GP or a licensed prescriber.
- 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 and tirzepatide the same thing?
Yes. Tirzepatide is the generic (medical) name for the active ingredient in Mounjaro. Mounjaro is the brand name given by the manufacturer Eli Lilly. Both names refer to the same prescription-only injection used for weight management in the UK.
Why is Mounjaro called a dual GIP and GLP-1 agonist?
Because tirzepatide activates two natural hormone pathways in your body — GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1). Both help regulate appetite and blood sugar. This dual mechanism is what distinguishes Mounjaro from single-pathway GLP-1 injections like Wegovy.
Is Mounjaro the same as Ozempic or Wegovy?
No. Mounjaro (tirzepatide) is a different medication from Ozempic and Wegovy. Ozempic and Wegovy both contain semaglutide but have different approved uses. Wegovy is licensed for weight management; Ozempic is licensed for type 2 diabetes. Mounjaro is a separate dual GIP/GLP-1 medication also licensed for weight management in the UK.
Do I need a prescription to get Mounjaro in the UK?
Yes. Mounjaro is prescription-only and requires a clinical assessment. Access in the UK is through either NHS specialist weight management services (with significant waiting times in many areas) or private online prescribing through a UK-licensed prescriber following an online consultation.
What does the KwikPen have to do with Mounjaro's name?
KwikPen is the name of the pre-filled injection device Mounjaro comes in — not a different medication. The full product name is "Mounjaro KwikPen". Each pen contains four once-weekly doses of tirzepatide at your prescribed strength.
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.