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 Mounjaro Weight Loss and UK Costs Explained
Mounjaro (tirzepatide) is a prescription-only weekly weight loss injection licensed in the UK. Clinical trials showed people lost an average of 15–21% of their body weight using Mounjaro, though individual results vary significantly. This guide explains what the research shows about average weight loss, how much Mounjaro costs privately in the UK, and the different ways to access it through the NHS or private online prescription services. Your actual results will depend on your starting weight, dose, diet, and activity level.
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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.
Average Weight Loss from Mounjaro — Clinical Trial Data
The SURMOUNT-1 clinical trial, which tested Mounjaro in adults with obesity or overweight plus weight-related health conditions, found:
- 5 mg dose: approximately clinically studied weight loss on average (roughly 10–15 kg for a person starting at 100 kg)
- 10 mg dose: approximately clinically studied weight loss (around 20 kg for the same person)
- 15 mg dose: approximately clinically studied weight loss (roughly 21 kg for a 100 kg baseline)
These results were achieved over 72 weeks alongside a reduced-calorie diet and increased physical activity. Results were measured at the maximum tolerated dose each participant reached during the dose titration phase. It's important to remember that these are trial averages — some participants lost more, others less. Individual weight loss depends on your starting weight, genetics, how well you tolerate the medication, and your commitment to lifestyle changes. Use our free GLP-1 weight loss calculator above to estimate potential results at different doses based on your personal circumstances.
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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.
Mounjaro Cost and Access in the UK — NHS vs Private
NHS access: Mounjaro is available through NHS specialist tier 3 and tier 4 weight management services following NICE approval, but availability varies significantly by region. You'll need a GP referral to a local weight management service; waiting times can be months to years depending on your area.
Private access: A weekly weight loss injection like Mounjaro is available through UK-licensed online prescribers. Costs typically range from £129–£320 per month depending on your dose. Each KwikPen contains 4 weeks of injections. You'll complete an online health questionnaire and consultation with a registered prescriber, who assesses suitability before issuing a prescription dispensed by a GPhC-registered pharmacy. Private treatment is faster but not covered by the NHS.
Try our free BMI calculator above to check whether your starting BMI might qualify you for treatment in either route.
- 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 averages of 15–clinically studied weight loss depending on dose. For example, someone starting at 100 kg (15st 10lbs) might lose 15–21 kg (2st 5lbs to 3st 4lbs) on average. However, individual results vary widely. Your actual loss depends on your metabolism, lifestyle, and how well you tolerate the medication.
How does Mounjaro compare to Wegovy for weight loss?
Mounjaro (dual GIP/GLP-1 agonist) and Wegovy (GLP-1 agonist only) showed similar average weight loss in trials — roughly 15% body weight with Wegovy and 15–21% with Mounjaro at maximum doses. Mounjaro's dual mechanism may offer slightly more, but clinical comparisons show individual variation is more significant than the difference between the two drugs.
Is Mounjaro weight loss permanent after stopping?
Weight loss from Mounjaro is not typically permanent after stopping. Clinical data suggests people regain weight if they discontinue the medication without maintaining lifestyle changes. Mounjaro is designed as an ongoing treatment alongside diet and exercise, not a short-term solution.
How much does Mounjaro cost privately per month in the UK?
Private Mounjaro costs typically range from £129–£320 per month depending on your dose and the online pharmacy or prescriber. Costs increase as you move up through dose escalation (from 2.5 mg to 15 mg). Each KwikPen provides 4 weekly injections. Always confirm the exact price with your chosen provider before starting.
How do I access Mounjaro through the NHS in the UK?
Ask your GP for a referral to your local NHS tier 3 weight management service. Eligibility criteria include BMI ≥30 or BMI ≥27 with weight-related health conditions. NHS access is free but availability varies by region and waiting lists can be lengthy. Private online prescription is faster but costs apply.
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.