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 0.5 Wegovy Equivalent to in Mounjaro?
When comparing Wegovy and Mounjaro, many people ask what dose of Mounjaro is equivalent to 0.5mg Wegovy. Based on clinical experience and prescribing guidance, approximately 2.5mg to 5mg of Mounjaro is considered roughly equivalent to 0.5mg Wegovy — though there is no official conversion chart. Both are prescription-only GLP-1 and GIP receptor agonist medications licensed in the UK for weight management. Individual responses vary significantly, and any dose comparison or switch between medications must be managed by your prescriber. Use our free GLP-1 weight loss calculator to explore projected outcomes at different doses.
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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.
Approximate Mounjaro and Wegovy Dose Equivalence
There is no official established dose conversion between Mounjaro (tirzepatide) and Wegovy (semaglutide), as they work through different mechanisms. However, clinical practice and prescribing guidance suggest these approximate equivalences:
- 0.5mg Wegovy ≈ 2.5–5mg Mounjaro
- 1mg Wegovy ≈ 5mg Mounjaro
- 1.7mg Wegovy ≈ 7.5–10mg Mounjaro
- 2.4mg Wegovy (max) ≈ 10–15mg Mounjaro
These are clinical approximations based on weight loss outcomes in trials, not pharmacological equivalents. Mounjaro is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways, whilst Wegovy (semaglutide) activates only the GLP-1 pathway. This difference in mechanism means direct dose-for-dose comparison is not straightforward. Prescribers may use these approximate guides when considering a switch, but individual factors — age, health conditions, previous response, and tolerance — always influence the actual dose chosen.
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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.
Why These Medications Are Not Directly Equivalent
Mounjaro and Wegovy are both prescription-only weight management injections available in the UK, but they are not interchangeable at equivalent doses. Mounjaro's dual mechanism (stimulating both GIP and GLP-1 receptors) produces a different effect profile compared to Wegovy's single GLP-1 mechanism. Clinical trials (SURMOUNT for Mounjaro and STEP trials for Wegovy) show that Mounjaro may produce slightly greater average weight loss — approximately 15–21% of body weight with Mounjaro vs approximately 15% with Wegovy — though results vary widely between individuals. If your GP or prescriber suggests switching between these medications, they will assess your individual health, previous response, and current dose to determine the most suitable new dose. Never adjust doses yourself between these medications.
- 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.
Can I switch from 0.5mg Wegovy to Mounjaro at the same dose?
No. 0.5mg Wegovy is not equivalent to 0.5mg Mounjaro. A prescriber would typically suggest starting Mounjaro at 2.5mg or 5mg depending on your health and previous response to Wegovy. Any switch must be managed by your GP or licensed prescriber — do not self-adjust.
Which is more effective — Mounjaro or Wegovy?
Clinical trials suggest Mounjaro may produce slightly greater average weight loss, but individual results vary significantly. Effectiveness depends on your personal response, adherence, diet, activity level, and health status. Your prescriber will recommend the most suitable option for you.
Is Mounjaro available on the NHS in the UK?
Yes, Mounjaro (tirzepatide) is now approved by NICE for use within NHS specialist weight management services. However, NHS availability varies by region and eligibility. Many people access Mounjaro through private prescribing following an online clinical assessment.
Why is there no official dose conversion chart?
Because Mounjaro and Wegovy use different mechanisms — Mounjaro activates two hormone pathways (GIP and GLP-1) whilst Wegovy activates only GLP-1. Approximate equivalences are based on weight loss trial data, not pharmaceutical equivalency. Your prescriber will determine the most appropriate starting dose.
Can I use our GLP-1 weight loss calculator to compare these doses?
Yes. Try our free GLP-1 weight loss calculator above to explore projected weight loss outcomes at different doses of both Mounjaro and Wegovy, alongside your personal BMI and health context. This can help you understand the potential range of outcomes when discussing options with your prescriber.
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.