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 Equivalent to Wegovy?
A 5mg dose of Mounjaro (tirzepatide) is approximately equivalent to around 0.5mg of Wegovy (semaglutide) in terms of weight loss effect, though individual results vary significantly. Both are prescription-only, once-weekly GLP-1 and GLP-1/GIP medications licensed in the UK for weight management. However, these are not direct medical equivalents—they work through different mechanisms and require different dose escalation schedules. Your prescriber will determine which medication and dose is most appropriate for your individual health situation following a clinical assessment.
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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.
Approximate Mounjaro and Wegovy Dose Comparison
While there is no official NHS or MHRA-approved conversion chart between Mounjaro and Wegovy, clinical practice suggests these approximate dose equivalences based on clinical trial data and pharmacological similarities:
- Mounjaro 5mg ≈ Wegovy 0.5mg (both maintenance doses)
- Mounjaro 10mg ≈ Wegovy 1.7mg (mid-to-high escalation)
- Mounjaro 15mg ≈ Wegovy 2.4mg (maximum doses)
These comparisons are based on the SURMOUNT-1 trial (Mounjaro) and STEP trials (Wegovy), where both medications were used alongside reduced-calorie diets. Important: Mounjaro is a dual GIP/GLP-1 agonist, whilst Wegovy is a GLP-1-only agonist. This means they work slightly differently—Mounjaro's dual mechanism may produce different results than Wegovy at similar dose levels. Switching between medications or adjusting doses must always be managed by your prescriber.
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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 Interchangeable
Mounjaro and Wegovy cannot simply be swapped at equivalent doses without prescriber guidance. The key reason is their different mechanisms: Mounjaro activates both GIP and GLP-1 receptor pathways, whilst Wegovy activates GLP-1 only. This dual action in Mounjaro may contribute to greater average weight loss in clinical trials (approximately 15–21% of body weight vs. 15% for Wegovy). Additionally, Mounjaro uses a different KwikPen device and requires a different dose titration schedule starting at 2.5mg, whereas Wegovy starts at 0.25mg. If you are considering switching between these medications, a licensed prescriber will assess your health, review your response to the current treatment, and recommend the most appropriate alternative with proper dose guidance.
- 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?
They are approximately equivalent in terms of intended weight loss effect, but not identical. Mounjaro is a dual GIP/GLP-1 agonist whilst Wegovy is GLP-1-only. At these doses, both are escalation or maintenance doses in their respective titration schedules. Individual response varies significantly, so equivalent doses do not assures equivalent results.
Can I switch from 5mg Mounjaro to Wegovy without medical advice?
No. Any switch between prescription weight loss medications must be managed by your prescriber or GP. Your prescriber will assess your health, review your response to Mounjaro, and recommend the appropriate Wegovy dose with proper guidance. Never change or stop medications without professional advice.
Why is there no official conversion between Mounjaro and Wegovy?
Mounjaro and Wegovy have different active ingredients (tirzepatide vs. semaglutide), different mechanisms of action, and were tested in separate clinical trials. The MHRA and NHS do not provide official conversion tables. Approximate equivalences are based on clinical practice experience and trial data, but prescriber assessment remains essential.
Which medication causes more weight loss—5mg Mounjaro or 0.5mg Wegovy?
Clinical trials suggest Mounjaro produces slightly greater average weight loss than Wegovy. SURMOUNT-1 showed 5mg Mounjaro resulted in approximately 15% average weight loss, whilst STEP trials showed 0.5mg Wegovy resulted in approximately 3–4% average weight loss. However, individual results vary widely based on diet, activity, and personal metabolism.
Can I use our GLP-1 weight loss calculator to compare these doses?
Yes. Our free GLP-1 weight loss calculator can help you estimate potential weight loss at different doses of both Mounjaro and Wegovy. However, these are projections only—actual results depend on your individual circumstances, lifestyle changes, and how your body responds to the medication.
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.