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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Mounjaro 5mg vs Wegovy — What's the Difference?
The 5mg dose is often called the "golden dose" for Mounjaro because many patients find it effective with manageable side effects. But how does it compare to Wegovy, the other major weight loss injection available in the UK? This guide compares the two medications directly, covering mechanism, clinical trial data, and how your prescriber decides which is right for you. Both are prescription-only and require clinical assessment before use.
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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.
How Mounjaro and Wegovy Work — The Key Difference
Mounjaro (tirzepatide) uses a dual mechanism: it activates both GIP and GLP-1 hormone pathways. This dual action may help regulate appetite and support feeling fuller after smaller meals more effectively than a single pathway.
Wegovy (semaglutide) activates the GLP-1 pathway only. It works well for many patients but uses a single hormone mechanism rather than two.
In the SURMOUNT-1 clinical trial, patients on Mounjaro 5mg lost an average of approximately 15% body weight over 72 weeks. Wegovy (in the STEP-1 trial) showed average weight loss of around 14.9% at the maximum 2.4mg dose. Both results were achieved alongside reduced-calorie diet and increased physical activity. Individual results vary significantly. Use our free GLP-1 weight loss calculator to estimate potential outcomes based on different doses and your current weight.
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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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Which Medication is Right for You?
Your GP or prescriber will choose between Mounjaro and Wegovy based on your individual health profile, not just weight loss potential. Factors they consider include your medical history, current medications, blood sugar control, and how you've responded to similar treatments in the past.
Mounjaro 5mg is the first maintenance dose for many patients and is often increased gradually. Wegovy requires dose escalation from 0.25mg up to the maximum 2.4mg.
Both medications are prescription-only in the UK. Access is through NHS specialist weight management services (with regional variation and waiting lists) or private online prescription services following clinical assessment. Your prescriber will assess whether either medication is suitable for your circumstances and health status.
- 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.
Is Mounjaro 5mg better than Wegovy?
Clinical trial data shows both medications can support meaningful weight loss. Mounjaro 5mg achieved ~15% average loss in trials; Wegovy achieved ~14.9% at maximum dose. "Better" depends on your individual health, medical history, and how your body responds. Your prescriber will recommend the most suitable option for you.
Why is 5mg called the "golden dose" for Mounjaro?
Many patients find the 5mg dose effective for weight loss while experiencing manageable side effects. It's the first maintenance dose (after 4 weeks at 2.5mg). However, some patients escalate further for additional effect. The right dose varies between individuals.
Can I switch from Wegovy to Mounjaro 5mg?
Yes, switching is possible, but must be managed by your prescriber. There is no official conversion chart. Approximate equivalence would place Wegovy 0.5mg near Mounjaro 5mg, but this is approximate only. Your prescriber will assess whether switching is appropriate and how to do so safely.
How long does it take to see weight loss results on Mounjaro 5mg?
Most patients see noticeable weight loss begin within 4–8 weeks at the 5mg dose. Clinical trials tracked results over 72 weeks. Results vary; some people see faster progress than others. Check your progress using our free progress tracker to monitor changes alongside the scale.
Are Mounjaro and Wegovy available on the NHS in the UK?
Both are licensed for NHS use, but access is through specialist tier 3 weight management services after GP referral. Availability and waiting times vary significantly by region and local commissioning decisions. Private prescription services are also available following online clinical assessment.
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.