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 5mg Mounjaro Equivalent to in Wegovy?
If you're on 5mg Mounjaro and wondering what the Wegovy equivalent might be, the approximate conversion is around 0.5mg Wegovy — though this is not an official established conversion. Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight management injections licensed in the UK, but they work through different mechanisms. Understanding how doses compare can help you have an informed conversation with your GP or prescriber, especially if you're considering switching between medications.
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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 Do Mounjaro and Wegovy Doses Compare?
Approximate dose equivalence based on clinical practice and trial data:
- 5mg Mounjaro ≈ 0.5mg Wegovy
- 10mg Mounjaro ≈ 1.7mg Wegovy
- 15mg Mounjaro ≈ 2.4mg Wegovy
However, these are approximate conversions only — there is no official MHRA-established conversion chart between the two medications. This is because Mounjaro (tirzepatide) works as a dual GIP and GLP-1 receptor agonist, activating two hormone pathways, whilst Wegovy (semaglutide) is a GLP-1-only agonist. Because of these different mechanisms, direct dose-for-dose equivalence is not straightforward. The 5mg Mounjaro starting maintenance dose typically produces comparable weight loss outcomes to Wegovy's 0.5mg dose in clinical practice, but individual responses vary significantly. Any switch between these medications must be managed by your prescriber, who will reassess your suitability and may adjust your dose based on your personal 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.
Why the Mechanisms Matter for Your Treatment
Mounjaro's dual action on both GIP and GLP-1 pathways means it has a different pharmacological profile than Wegovy's single GLP-1 mechanism. This difference affects not just dosing but also how your body may respond — some people experience better appetite suppression with Mounjaro, whilst others find Wegovy equally effective at lower doses. In UK clinical practice, the two medications are not simply interchangeable at proportional doses. If you're considering switching from 5mg Mounjaro to Wegovy, your GP or specialist weight management service will conduct a fresh clinical assessment rather than simply applying a mathematical conversion. You can use our free GLP-1 weight loss calculator to explore potential outcomes with both medications, and our BMI calculator to track your progress 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 the same strength as 0.5mg Wegovy?
Approximately, in terms of clinical outcomes observed in practice, yes — but they are not pharmacologically identical. Mounjaro is a dual GIP+GLP-1 agonist whilst Wegovy is GLP-1-only, so the same weight loss effect may come through different biological mechanisms. Individual response varies.
Can my GP switch me from 5mg Mounjaro to Wegovy directly?
Your prescriber can, but they will assess whether the switch is appropriate for you and may adjust your Wegovy dose based on your personal response. Never switch between medications without prescriber guidance — they may recommend a gradual transition or a different starting dose.
Which medication works better for weight loss — Mounjaro or Wegovy?
Clinical trials show both are effective. Average weight loss with Mounjaro is approximately 15–21% of body weight, and with Wegovy approximately 15%. Individual results vary significantly based on your health, lifestyle, and how your body responds. Your prescriber will help determine which is more suitable for you.
Does 5mg Mounjaro produce more weight loss than 0.5mg Wegovy?
Not necessarily — outcomes are broadly comparable in clinical practice, though individual results vary. Some people lose more with one medication than the other. Your response depends on your unique physiology, not just the dose equivalent.
What should I do if I want to switch from Mounjaro to Wegovy?
Contact your prescriber first. Do not stop Mounjaro and start Wegovy without medical guidance. Your prescriber will assess your suitability, discuss the reasons for switching, and create a plan that may involve a transition period or dose adjustment.
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.