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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Mounjaro Success Stories Before and After in the UK
Mounjaro (tirzepatide) has generated significant interest in the UK, with many adults curious about real-world weight loss outcomes. While personal testimonials are common online, clinical trial data provides the most reliable picture of what this prescription-only injection can achieve. This guide explains what the evidence shows about Mounjaro's effectiveness in UK context, how NHS eligibility works, and what results you might realistically expect when working with a healthcare professional.
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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.
What Clinical Trials Show About Mounjaro Results
The SURMOUNT-1 clinical trial published evidence on Mounjaro's effectiveness over 72 weeks. Participants taking the maximum 15 mg dose achieved an average weight loss of approximately 20.9% of their body weight, whilst those on 10 mg lost around 19.5% on average. These results occurred alongside a reduced-calorie diet and increased physical activity — medication alone does not produce weight loss.
Individual results vary significantly. Some participants lost more, others less. The trial also showed that weight loss tends to plateau around week 40–52, after which it stabilises rather than continuing to increase. For context, if you weigh 100 kg, a 20% loss would mean losing approximately 20 kg (roughly 3 stone 2 lbs). However, your personal outcome depends on your starting weight, genetics, adherence to lifestyle changes, dose reached, and individual metabolic factors.
Importantly, these are clinical trial averages in controlled settings with professional support — real-world results in everyday UK practice may differ.
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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.
Why Personal "Before and After" Stories Can Be Misleading
Social media and online forums feature dramatic weight loss testimonials, which can feel motivating but are often not representative. People tend to share exceptional results, not average or modest ones — creating a skewed picture. Additionally, without medical verification, it's impossible to know whether weight loss was from Mounjaro alone, from lifestyle changes, from other medications, or from a combination.
The NHS and MHRA (UK medicines regulator) recommend relying on clinical trial data rather than anecdotal stories when assessing medication effectiveness. Your GP or prescriber can discuss what realistic weight loss might look like for your individual circumstances based on evidence, not online testimonials.
- 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.
What is a realistic amount of weight loss to expect with Mounjaro?
Clinical trials show average weight loss of 15–21% of body weight over 72 weeks at higher doses, alongside diet and exercise. Individual results vary. Your GP can discuss realistic expectations based on your health, starting weight, and ability to make lifestyle changes.
How long does it take to see weight loss results with Mounjaro?
Most participants in SURMOUNT trials saw noticeable weight loss from weeks 4–12 onwards. Significant results typically emerge by 16–20 weeks. Weight loss continues through the trial period but may plateau around 40–52 weeks.
Does Mounjaro work on the NHS in the UK?
NICE has approved tirzepatide for NHS use within specialist tier 3 weight management services. Availability varies by region and waiting lists can be lengthy. Your GP can refer you to your local specialist service if you meet eligibility criteria (BMI 30+ or 27+ with comorbidities).
What's the difference between Mounjaro and Wegovy for weight loss?
Mounjaro (tirzepatide) is a dual GIP+GLP-1 agonist; Wegovy (semaglutide) is a GLP-1 agonist only. SURMOUNT trials showed Mounjaro achieved slightly higher average weight loss (20.9%) compared to Wegovy trials (around 15%), but individual results vary and both are prescription-only medications.
Can I calculate my potential weight loss with Mounjaro?
Our free GLP-1 weight loss calculator can help you estimate potential weight loss at different Mounjaro doses based on your starting weight. Remember these are projections based on trial averages — your actual results will depend on your individual circumstances and lifestyle changes.
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.