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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What is the 5mg Mounjaro to Wegovy equivalent dose?
If you're taking 5mg Mounjaro (tirzepatide) or considering switching to Wegovy (semaglutide), you may wonder what the equivalent dose would be. While there's no official established conversion chart, clinical practice suggests that 5mg Mounjaro is approximately equivalent to 0.5mg Wegovy in terms of effect. Both are prescription-only GLP-1 and GIP/GLP-1 medications used alongside diet and exercise for weight management in UK adults. Individual responses vary significantly, and any medication change must be managed by your prescriber.
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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.
How Mounjaro and Wegovy doses compare
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) work as receptor agonists that help reduce appetite and support weight loss, but they use different mechanisms. Mounjaro is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways, while Wegovy is a GLP-1-only agonist. This difference in mechanism means direct dose-for-dose comparisons are not straightforward.
Approximate equivalence based on clinical practice suggests:
- 5mg Mounjaro ≈ 0.5mg Wegovy
- 10mg Mounjaro ≈ 1.7mg Wegovy
- 15mg Mounjaro ≈ 2.4mg Wegovy (maximum dose)
Important: These are approximate clinical guideline estimates only—not official pharmaceutical conversions. Weight loss outcomes in clinical trials (SURMOUNT for Mounjaro, STEP for Wegovy) show both medications deliver meaningful results, but individual variation is substantial. Your prescriber will assess which medication and dose is appropriate based on your personal health profile and response.
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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.
What you need to know about switching between these medications
Any switch between Mounjaro and Wegovy must be managed by your UK-licensed prescriber—never stop or change doses without medical guidance. Both medications are prescription-only and require a clinical assessment before dispensing. They're not interchangeable, and switching involves considerations like your current dose, medical history, and tolerance.
If you're exploring whether Mounjaro or Wegovy is right for you, use our free GLP-1 weight loss calculator to see projected weight loss at different doses. Both medications work best alongside a reduced-calorie diet and increased physical activity. Your GP or private prescriber can discuss which option suits your circumstances and provide appropriate monitoring throughout treatment.
- 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 5mg Mounjaro exactly the same strength as 0.5mg Wegovy?
No. While 0.5mg Wegovy is an approximate clinical equivalent to 5mg Mounjaro, they're not identical. Mounjaro's dual mechanism (GIP+GLP-1) differs from Wegovy's single GLP-1 pathway. Individual responses vary, and your prescriber determines the right dose based on your health profile and tolerance.
Can I switch from 5mg Mounjaro to Wegovy without medical supervision?
No. Any medication switch must be managed by your prescriber. Never stop or change doses independently. Your GP or licensed prescriber will assess whether switching is appropriate, what dose to start, and how to monitor your response safely.
Which medication causes more weight loss: Mounjaro or Wegovy?
Clinical trials suggest Mounjaro may deliver slightly greater average weight loss (approximately 15–21% body weight) compared to Wegovy (approximately 15% body weight). However, individual results vary significantly. Effectiveness depends on your dose, adherence, diet, activity level, and personal metabolism.
Are Mounjaro and Wegovy available on the NHS in the UK?
Both are licensed for use in the UK. NHS access is through tier 3 specialist weight management services and varies by region. Private access is available through UK-licensed online prescribers following a clinical assessment. Waiting times and availability differ significantly across the country.
What are the side effects of Mounjaro compared to Wegovy?
Both share common side effects including nausea, diarrhoea, constipation, and stomach discomfort—typically mild and temporary during the dose escalation phase. Individual tolerance varies. Your prescriber will discuss side effect management and when to seek medical advice if symptoms are severe or persistent.
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.