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
Free tracker included with every download this week
How Much Weight Do People Lose On Mounjaro?
Clinical trials show that people on Mounjaro lose an average of 15–21% of their body weight over 72 weeks, depending on the dose reached. However, individual results vary significantly based on adherence, diet, physical activity, and personal metabolism. Many people wonder how this compares to Wegovy (semaglutide), which shows similar but slightly lower average outcomes. It's important to understand that these are clinical trial averages, not studied results, and that both medications work best alongside a reduced-calorie diet and increased physical activity. Our free GLP-1 weight loss calculator can help you estimate potential outcomes at different doses.
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.
Mounjaro vs Wegovy: Clinical Trial Data Compared
The SURMOUNT-1 clinical trial for Mounjaro (tirzepatide) showed average weight loss results over 72 weeks alongside lifestyle changes:
- 5 mg dose: approximately clinically studied weight loss
- 10 mg dose: approximately clinically studied weight loss
- 15 mg dose (maximum): approximately clinically studied weight loss
By comparison, the STEP-1 clinical trial for Wegovy (semaglutide) showed an average weight loss of approximately 14.9% at the maximum dose (2.4 mg) over 68 weeks.
The key difference is mechanism: Mounjaro is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways, while Wegovy is a GLP-1 receptor agonist only. This dual action in Mounjaro may contribute to slightly higher average weight loss in trials, though prescriber preference and individual suitability determine which medication is appropriate for each person following clinical assessment.
Clinically BackedWeight Loss
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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.
Individual Results Vary — What Affects Your Outcome?
Clinical trial averages are just that—averages. Your actual weight loss depends on many individual factors: how well you stick to a reduced-calorie diet, your level of physical activity, your starting weight, your genetics, and your metabolism.
Some people on Mounjaro lose more than the average; others lose less. Some find the medication causes significant appetite reduction early on, while others experience a more gradual effect. Both Mounjaro and Wegovy require a prescription from a UK-licensed prescriber following a clinical assessment—your prescriber will discuss which medication may be suitable for your specific situation. Track your progress with our free progress tracker, and remember that both medications are most effective when combined with sustainable lifestyle changes rather than relied upon alone.
- 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.
Does Mounjaro clinically studied weight loss?
No. Mounjaro is not a assures. Clinical trials show average weight loss of 15–21% body weight, but individual results vary significantly. Your actual outcome depends on diet adherence, physical activity, genetics, and how your body responds to the medication.
Is Mounjaro better than Wegovy for weight loss?
Mounjaro showed slightly higher average weight loss in clinical trials (20.9% at maximum dose vs 14.9% for Wegovy), but individual results vary considerably. Your prescriber will recommend based on your personal health profile and suitability, not trial averages alone.
How long does it take to see weight loss results on Mounjaro?
Most people begin to notice appetite changes within 1–2 weeks of starting Mounjaro. Visible weight loss typically occurs after 4–8 weeks on a consistent dose alongside diet and exercise changes. Results accelerate as you reach higher doses over several months.
What happens if you stop taking Mounjaro—do you regain the weight?
Weight regain is possible after stopping any weight loss medication. Clinical data suggests some weight return, though people often maintain some loss. Long-term weight management requires continued lifestyle changes. Discuss stopping plans with your prescriber.
How much does Mounjaro cost in the UK, and does it affect results?
Mounjaro is available through NHS specialist services (if eligible) or private prescription at roughly £129–£320 monthly depending on dose. Cost doesn't affect how the medication works—efficacy is the same regardless of whether it's NHS or privately prescribed.
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.