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 1mg Wegovy Equivalent to in Mounjaro?
If you're considering switching from Wegovy (semaglutide) 1mg to Mounjaro (tirzepatide), you may wonder what the equivalent dose would be. Although both are once-weekly injection medications licensed for weight management in the UK, they work slightly differently — Wegovy is a single GLP-1 receptor agonist, while Mounjaro is a dual GIP and GLP-1 receptor agonist. There is no official NHS conversion chart, but clinical practice suggests approximate dose equivalences. Any switch between medications must be managed by your prescriber following a clinical assessment.
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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 Dose Equivalences Between Wegovy and Mounjaro
Approximate equivalences: Wegovy 1mg is roughly equivalent to Mounjaro 5–7.5mg based on clinical outcomes in weight loss trials. However, this is an approximate comparison only — individual response varies significantly, and any switch requires prescriber guidance.
Why equivalence is approximate: Wegovy and Mounjaro have different mechanisms. Mounjaro's dual GIP/GLP-1 action may produce different results at the same dose level. Clinical trials (STEP for Wegovy, SURMOUNT for Mounjaro) used different study designs and patient populations, making direct comparison complex.
- Wegovy 0.5mg ≈ Mounjaro 2.5–5mg
- Wegovy 1mg ≈ Mounjaro 5–7.5mg
- Wegovy 1.7mg ≈ Mounjaro 10mg
- Wegovy 2.4mg (maximum) ≈ Mounjaro 15mg (maximum)
These are clinical estimates, not prescribing guidelines. Your prescriber may adjust based on your individual response, health history, and tolerability.
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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 Switch From Wegovy to Mounjaro and How to Proceed
Reasons for switching may include suboptimal weight loss response, side effects, availability, or cost. Some people find Mounjaro's dual mechanism more effective, whilst others tolerate Wegovy better. The switch must be managed by a UK-licensed prescriber through either NHS specialist weight management services or a private online prescribing consultation.
The switching process: Your prescriber will assess your current progress, any side effects experienced, and your health status. You may start at a lower Mounjaro dose than the estimated equivalent and titrate upwards over weeks. There is typically a brief gap between stopping one medication and starting another. Use our free GLP-1 weight loss calculator to track projected outcomes at different doses, and our BMI calculator to monitor your health progress throughout any medication change.
- 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 directly from Wegovy 1mg to Mounjaro without a gap?
No. Prescription weight loss medications require a clinical assessment before any change. Your prescriber will advise whether to stop Wegovy immediately or step down, and when to begin Mounjaro. There is usually a gap of a few days to a week to allow your system to adjust. Never switch medications without prescriber guidance.
Will Mounjaro work better than Wegovy for weight loss?
Clinical trials show both medications support weight loss, but individual results vary significantly. Mounjaro's dual GIP/GLP-1 mechanism may produce different outcomes for different people. Some find it more effective than Wegovy; others find Wegovy suits them better. Your prescriber can advise based on your personal health profile.
What if Mounjaro's starting dose makes me feel unwell?
If you experience significant side effects when starting Mounjaro (nausea, vomiting, stomach pain), contact your prescriber immediately. Dose adjustment or temporary reduction may be appropriate. Most side effects reduce as your body adjusts, but your prescriber can support you through this period.
Is Mounjaro available on the NHS if I've previously tried Wegovy?
NHS availability depends on your local integrated care board (ICB) and specialist tier 3 weight management service provision. Previous Wegovy use does not automatically qualify you for NHS Mounjaro. Your GP can refer you to specialist services, but waiting lists vary significantly by region. Private prescribing is also available.
How long should I stay on Mounjaro before assessing if it's working?
Most prescribers recommend staying on each dose for at least 4 weeks before increasing. Significant weight loss effects typically become noticeable after 8–12 weeks of treatment. Use our free progress tracker to log your weight and monitor trends objectively alongside any dose adjustments.
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.