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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Are Mounjaro and Wegovy Equivalent Doses?
Mounjaro (tirzepatide) and Wegovy (semaglutide) are both prescription-only weight management injections licensed in the UK, but they work differently and use different dose ranges. While approximate dose equivalences exist based on clinical practice, there is no official NHS or MHRA established conversion chart. Both medications require individual clinical assessment, and any switch between them must be managed by your prescriber. Understanding how their doses compare can help you ask informed questions about your treatment options.
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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 Equivalent Doses
Based on clinical trial data and prescribing experience, approximate dose equivalences between Mounjaro and Wegovy are:
- Mounjaro 5 mg ≈ Wegovy 0.5 mg
- Mounjaro 10 mg ≈ Wegovy 1.7 mg
- Mounjaro 15 mg ≈ Wegovy 2.4 mg (maximum dose)
However, these are approximate equivalences only. Mounjaro is a dual GIP and GLP-1 receptor agonist, while Wegovy is a single GLP-1 agonist. This means Mounjaro's dual mechanism may produce different effects at lower doses compared to Wegovy. Individual response varies significantly — some patients lose more weight on one medication than the other at supposedly equivalent doses. Your GP or prescriber will assess which medication is most suitable for you based on your personal health profile, medical history, and treatment response. Never attempt to self-adjust or switch between medications without medical guidance.
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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.
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Why These Medications Are Not Directly Interchangeable
Although approximate equivalences exist, Mounjaro and Wegovy are fundamentally different medications. Mounjaro's dual action on both GIP and GLP-1 pathways means it may work differently than single-action Wegovy at the same conceptual "dose level". Additionally, both medications are dosed on individual escalation schedules — Mounjaro starts at 2.5 mg and escalates every 4 weeks, while Wegovy starts at 0.25 mg and escalates weekly over weeks 1–16. Clinical trial results also differ: Mounjaro clinical trials (SURMOUNT-1) showed approximately 15–21% average weight loss, while Wegovy trials (STEP-1) showed approximately 14.9% average weight loss, though individual outcomes vary considerably. Use our free GLP-1 weight loss calculator to explore potential weight loss outcomes, and discuss medication choice with your GP or prescriber.
- 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 Mounjaro stronger than Wegovy?
Mounjaro and Wegovy work via different mechanisms, so "stronger" is not straightforward. Mounjaro's dual GIP/GLP-1 action may produce different effects than Wegovy's single GLP-1 action. Clinical trial data suggests Mounjaro achieved slightly higher average weight loss, but individual results vary. Your prescriber will choose based on your personal health profile, not medication strength.
Can I switch from Wegovy to Mounjaro?
Switching between medications requires GP or prescriber guidance. There is no official conversion protocol — your prescriber may restart titration or adjust dosing based on your response to Wegovy. Never self-switch or use another person's doses. Any medication change must follow a clinical assessment and supervised plan.
What is the Mounjaro KwikPen equivalent to Wegovy?
Mounjaro is administered via KwikPen (a pre-filled auto-injection device), while Wegovy uses a different pen design. Both deliver once-weekly injections but are not interchangeable devices. The medication inside differs — Mounjaro contains tirzepatide, Wegovy contains semaglutide. Equipment is specific to each medication.
Are Mounjaro and Wegovy both available on the NHS in the UK?
Both Mounjaro and Wegovy are UK-licensed for weight management and available through NHS specialist tier 3 weight management services, though regional availability varies and waiting lists can be long. Both are also available privately through UK-licensed online prescribers. Access depends on your local NHS integrated care board and individual eligibility.
Which medication should I take — Mounjaro or Wegovy?
This decision is made by your GP or prescriber based on your individual health, medical history, weight management goals, and any relevant contraindications. Both are effective, prescription-only medicines. Your prescriber will assess which is more appropriate for you. Use the BMI calculator on this page to check your current BMI and discuss your options with your GP.
Ready to take control of your weight loss journey?
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