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 and Mounjaro Equivalent Doses Explained
Wegovy (semaglutide) and Mounjaro (tirzepatide) are both prescription-only weight management injections licensed in the UK, but they use different dosing schedules and mechanisms. While approximate dose equivalence exists, they are not interchangeable — any switch between medications must be managed by your prescriber following a clinical assessment. Understanding how the doses compare can help you discuss options with your GP or prescriber. Both medications work alongside a reduced-calorie diet and increased physical activity for best results.
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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 Wegovy and Mounjaro Doses Compare
Approximate dose equivalence between Wegovy and Mounjaro has been established through clinical practice, though there is no official NHS or MHRA conversion chart. The following table shows how typical maintenance and escalation doses align:
- Wegovy 0.5 mg ≈ Mounjaro 5 mg
- Wegovy 1.7 mg ≈ Mounjaro 10 mg
- Wegovy 2.4 mg ≈ Mounjaro 15 mg
However, these are approximate equivalences only. Mounjaro is a dual GIP and GLP-1 receptor agonist, whilst Wegovy is a GLP-1-only medication — this mechanism difference means they cannot be considered directly equivalent. Clinical trial data from SURMOUNT (Mounjaro) showed 15–21% average weight loss, compared to STEP trials (Wegovy) showing approximately 15% average weight loss. Individual results vary significantly, and dose escalation timing differs between the two medications.
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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.
Choosing Between Wegovy and Mounjaro
Both medications require a UK prescription and clinical assessment before dispensing — your prescriber will review your medical history, current medications, BMI, and any weight-related health conditions to determine which is more suitable for you. Factors your prescriber considers include gastrointestinal tolerance, previous medication responses, and specific health priorities. Neither medication is "better" — suitability is individual. Use our free GLP-1 weight loss calculator to explore projected outcomes at different doses, and our BMI calculator to understand your current health context. Your GP or licensed prescriber has access to the latest clinical guidance and can make a personalised recommendation based on your circumstances.
- 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 Wegovy to Mounjaro or vice versa?
Switching between the two medications is possible but must be managed by your prescriber. There is no automatic conversion — your prescriber will typically pause one medication and restart the other at an appropriate starting dose, monitoring your response carefully. Never attempt to self-switch doses between medications.
Which medication causes more side effects?
Both commonly cause nausea, diarrhoea, constipation, and stomach pain, especially when starting or increasing doses. Side effect profiles are similar, though individual tolerance varies. Mounjaro's dual mechanism may cause slightly different tolerability patterns in some people. Your prescriber can discuss specific concerns with you.
Are Wegovy and Mounjaro doses titrated the same way?
No. Wegovy escalates from 0.25 mg weekly over 16 weeks to a maximum 2.4 mg. Mounjaro escalates from 2.5 mg over 20 weeks to a maximum 15 mg. Minimum time on each dose differs — typically 4 weeks for Mounjaro, 4 weeks for Wegovy. Your prescriber determines your personal titration schedule.
Is one medication more effective than the other?
Clinical trials show similar average weight loss (15–21%) with both medications when used alongside lifestyle changes. Individual results vary — some people respond better to one medication than another. Effectiveness depends on adherence, diet, activity, and individual metabolism, not just the medication chosen.
How do I access Wegovy or Mounjaro in the UK?
Both are available via NHS specialist weight management services (tier 3) following GP referral, with significant regional variation and waiting lists. Both are also available through private online prescribing with a UK-licensed prescriber and GPhC-registered pharmacy, without NHS referral. A clinical assessment is required in both routes.
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.