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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Wegovy Weight Loss Chart: Clinical Results vs Mounjaro
When comparing weekly weight loss injection options in the UK, understanding the clinical evidence behind Wegovy and Mounjaro helps you have an informed discussion with your prescriber. Both are prescription-only GLP-1 and GIP/GLP-1 receptor agonist medications approved for weight management in UK adults. This guide compares their weight loss chart data, mechanisms, and eligibility, helping you understand how they differ—though individual results vary significantly, and the right choice depends on your personal health profile assessed by a licensed prescriber.
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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.
Clinical Trial Data: Wegovy vs Mounjaro Weight Loss
Wegovy (semaglutide) is a once-weekly GLP-1 receptor agonist studied in the STEP clinical trials. At the maximum dose of 2.4 mg, participants lost an average of approximately 14.9% of their body weight over 68 weeks, alongside a reduced-calorie diet and increased physical activity.
Mounjaro (tirzepatide) uses a dual GIP and GLP-1 mechanism, studied in the SURMOUNT trials. Results showed average weight loss of approximately 15% at 5 mg, 19.5% at 10 mg, and 20.9% at the maximum 15 mg dose over 72 weeks with the same lifestyle support.
The key difference: Mounjaro's dual mechanism may produce slightly higher average weight loss in clinical trials, but individual results vary considerably. Some people respond better to Wegovy; others achieve better results with Mounjaro. Neither outcome is assured, and your prescriber will assess which is suitable for you based on your semaglutide weight loss profile, health history, and other medications you take.
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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.
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Mechanism, Eligibility, and NHS Access
How they work differently: Wegovy activates the GLP-1 hormone pathway, reducing appetite and helping you feel fuller after smaller meals. Mounjaro activates both GIP and GLP-1 pathways—a dual action that may explain slightly higher average weight loss in trials, though this varies between individuals.
Eligibility is the same: Both require a BMI of 30 or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease). Lower BMI thresholds apply for South Asian, Chinese, Black African, and Black Caribbean adults.
Access in the UK: Both are available through NHS specialist tier 3 weight management services (with significant regional waiting lists) or private online prescribing following a clinical assessment. Your GP or prescriber will determine which is appropriate for you.
- 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.
How much weight do people typically lose with Wegovy?
In the STEP-1 clinical trial, participants on 2.4 mg Wegovy lost an average of 14.9% of their body weight over 68 weeks when combined with diet and exercise. This is approximately 10–15 kg for many adults, though individual results vary significantly. Some people lose more; others lose less. Results are not assured.
Is Mounjaro more effective than Wegovy for weight loss?
Clinical trials suggest Mounjaro may produce slightly higher average weight loss (15–21% depending on dose) compared to Wegovy (14.9%), but the difference is modest and individual responses vary greatly. Some people achieve better results with Wegovy. Your prescriber will assess which suits your health profile based on clinical assessment, not trial averages.
Can I switch from Wegovy to Mounjaro or vice versa?
You can only switch medications under guidance from your prescriber. Approximate dose equivalences exist (for example, Wegovy 2.4 mg is roughly equivalent to Mounjaro 10 mg), but any switch requires medical supervision. Your prescriber will manage the change carefully to ensure safety.
What is the wegovy UK prescription eligibility?
Wegovy is available on the NHS through specialist tier 3 weight management services or privately via online prescribing. You must have a BMI of 30 or above, or 27–29.9 with weight-related conditions. Lower thresholds apply for South Asian, Chinese, Black African, and Black Caribbean backgrounds. Always consult your GP first.
How does the GLP-1 weight loss work differently from GIP+GLP-1?
Wegovy (GLP-1 only) activates one appetite-regulating pathway. Mounjaro (GIP+GLP-1 dual) activates two pathways simultaneously, which may amplify satiety signalling. However, individual gut biology differs—some people respond better to single-mechanism GLP-1, others to dual-mechanism GIP/GLP-1. Your prescriber assesses which suits you.
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