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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Average Weight Loss With Mounjaro — What the Evidence Shows
Mounjaro (tirzepatide) is a prescription-only GLP-1 injection licensed for weight management in the UK. Clinical trials showed participants lost an average of 15–21% of their body weight over 72 weeks — though individual results vary significantly. Understanding how this translates to your personal healthy weight range requires looking at BMI context and your current health status. Your GP or prescriber can assess whether Mounjaro is suitable for you and help set realistic, personalised targets aligned with NHS healthy weight guidance.
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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.
Understanding Average Weight Loss in BMI Context
The SURMOUNT clinical trials measured Mounjaro's effects across different doses. At 5 mg weekly, participants lost approximately 15% of body weight on average. At 10 mg, this increased to around 19.5%, and at the maximum 15 mg dose, approximately 20.9% average weight loss was recorded.
To understand what this means for your personal health, it's important to frame it in terms of healthy weight range rather than absolute kg loss. A healthy BMI according to NHS guidelines is 18.5–24.9 for most UK adults. For example, a person 1.73m tall (5ft 8in) with a healthy weight range of 55–74 kg (8st 8lb to 11st 8lb) losing 20% of their current weight would move closer to the lower end of this healthy range.
- Results achieved alongside reduced-calorie diet and increased physical activity
- Average loss does not assures individual outcomes — some people lose more, some less
- Weight loss typically continues as long as medication is taken and lifestyle changes maintained
- For South Asian, Chinese, Black African, and Black Caribbean adults, lower BMI thresholds apply, which may affect eligibility and targets
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.
Using Your BMI as a Framework for Weight Loss Goals
Rather than focusing solely on "average" kg loss, calculate your ideal body weight range using your height and BMI. Use our free BMI calculator above to find your current BMI and your healthy weight range. If your current BMI is in the overweight or obese category, moving towards the healthy BMI range of 18.5–24.9 is the NHS-recommended goal.
For instance, at 100 kg and 1.73m tall, your BMI is approximately 33.4 (obese). A healthy weight range for your height would be 55–74 kg. A clinically studied weight loss from 100 kg equals 20 kg, bringing you to 80 kg — still overweight but significantly improved health outcomes. Our GLP-1 weight loss calculator can estimate potential results at different doses, while our weight converter helps you track progress between kg, stone, and pounds.
- 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's the average weight loss with Mounjaro in kg and stone?
Clinical trials showed average weight loss of 15–21% of body weight depending on dose. For example, a 100 kg person might lose 15–21 kg (2st 5lb to 3st 5lb) on average. However, individual results vary — some lose more, some less. Your prescriber will discuss realistic targets based on your health and circumstances.
How does Mounjaro weight loss compare to an ideal body weight?
The goal isn't just to lose weight, but to reach a healthy BMI range of 18.5–24.9 according to NHS guidelines. Use our free BMI calculator to find your healthy weight range for your height. Mounjaro helps you move towards this range, not necessarily to a specific number.
How quickly does weight loss happen with Mounjaro?
Weight loss is typically gradual. Most people see initial changes within 4–8 weeks, with more noticeable loss by 12–16 weeks. The trials measured results over 72 weeks. Sustainable weight loss at 0.5–1 kg per week is considered safe by NHS guidance.
Does everyone lose the same amount on Mounjaro?
No. Results vary significantly between individuals due to genetics, diet adherence, physical activity, baseline weight, and other health factors. While 15–21% is the average from clinical trials, some people lose more, others less. Your prescriber will monitor your progress and adjust doses if needed.
What happens to weight loss if I stop taking Mounjaro?
Weight typically stabilises when you stop the medication. Some people maintain weight loss if lifestyle changes (diet and exercise) are maintained long-term. Others gradually regain weight. Discuss long-term plans with your GP or prescriber to develop a sustainable strategy.
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.