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 and Healthy BMI Targets
Clinical trials showed that Mounjaro (tirzepatide) helped participants lose an average of 15–21% of their body weight over 72 weeks, though individual results vary significantly. Understanding how this translates to reaching a healthy BMI range is important context. A healthy weight for your height means a BMI between 18.5 and 24.9 according to NHS guidelines, though lower thresholds apply for South Asian, Chinese, Black African, and Caribbean backgrounds. Use our free BMI calculator to find your personal target weight range, which will help you understand what average weight loss looks like in practical terms for your height and demographic.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
How Mounjaro Weight Loss Relates to Healthy BMI Ranges
Average weight loss data from SURMOUNT-1 clinical trials:
- 5 mg dose: approximately clinically studied weight loss on average
- 10 mg dose: approximately clinically studied weight loss on average
- 15 mg dose (maximum): approximately clinically studied weight loss on average
These results were achieved alongside a reduced-calorie diet and increased physical activity — medication alone is not sufficient. For example, a person weighing 100 kg (15st 10lbs) losing 20% would reach 80 kg (12st 8lbs). Whether this puts them into a healthy BMI range depends on their height. Using our weight converter, you can translate these percentages into stone and pounds, then check where your target weight sits on the NHS healthy weight scale. Results vary based on individual factors including age, genetics, starting weight, diet adherence, and physical activity level.
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.
Finding Your Healthy Weight Range Using BMI
A healthy BMI of 18.5–24.9 translates to different weights depending on your height. For someone 5ft 8in (173 cm) tall, this means a healthy weight range is approximately 55–74 kg (8st 8lbs to 11st 8lbs). For someone 5ft 4in (163 cm), it's roughly 49–66 kg (7st 10lbs to 10st 5lbs). Our free BMI calculator instantly shows you the healthy weight range for your exact height and demographic. If you're currently above this range, knowing the percentage reduction needed helps set realistic Mounjaro goals. For instance, if your ideal weight range midpoint is 70 kg and you currently weigh 95 kg, you'd need approximately clinically studied weight loss — within the upper range of Mounjaro results. Always discuss your personal weight loss targets with your GP or 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.
What's the average weight loss percentage with Mounjaro?
Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks depending on dose (5 mg to 15 mg), alongside diet and exercise. Individual results vary significantly based on genetics, adherence, and starting weight. A 20% loss means someone starting at 100 kg would reach 80 kg on average — though some people lose more or less.
How does average Mounjaro weight loss translate to healthy BMI?
Whether Mounjaro's average weight loss reaches a healthy BMI depends on your height and starting weight. Use our free BMI calculator to find your healthy weight range for your height, then calculate if the average percentage loss gets you there. Your prescriber can discuss personalised targets with you based on your specific circumstances.
Is average weight loss with Mounjaro assured?
No. Clinical trial averages don't assures individual outcomes. Some people lose more than the average, some less. Results depend on diet adherence, physical activity, metabolism, genetics, and other health factors. Mounjaro is a tool to support lifestyle changes, not a standalone solution.
How long does it take to see average weight loss results on Mounjaro?
Clinical trials measured results over 72 weeks (approximately 18 months). Most weight loss typically occurs between weeks 4–20 as the body adjusts to the medication. After that, weight loss often continues but more gradually. Your prescriber will monitor progress and adjust doses as needed.
What's the difference between average weight loss and my personal target?
Average weight loss is population data from clinical trials. Your personal target should be based on your current weight, height, and healthy BMI range. Our free BMI calculator shows your ideal weight range. Discuss realistic, personalised targets with your GP — aiming for a healthy BMI rather than a specific number often works better long-term.
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.