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
Wegovy (semaglutide) and Mounjaro (tirzepatide) are prescription-only weight management injections licensed in the UK, but they work through different mechanisms and use different dose schedules. While approximate dose equivalents exist based on clinical practice, there is no official NHS conversion chart between the two. Understanding how their doses compare can help you discuss options with your GP or prescriber during 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.
How Mounjaro and Wegovy Doses Compare
Approximate dose equivalents between Mounjaro and Wegovy are based on clinical outcomes and trial data, not an established medical conversion:
- Mounjaro 5 mg is approximately equivalent to Wegovy 0.5 mg
- Mounjaro 10 mg is approximately equivalent to Wegovy 1.7 mg
- Mounjaro 15 mg is approximately equivalent to Wegovy 2.4 mg (maximum dose)
However, these equivalents are not officially recognised by NICE or the MHRA — they are based on average weight loss outcomes across clinical trials. Individual responses vary significantly. One person may achieve better results on Mounjaro, another on Wegovy, even at theoretically equivalent doses. Your prescriber will assess which medication and dose is right for you based on your medical history, not dose equivalence alone.
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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 Doses Aren't Directly Comparable
Mounjaro (a dual GIP and GLP-1 receptor agonist) and Wegovy (a GLP-1 receptor agonist only) work through different biological pathways. Mounjaro activates two hormone systems simultaneously, while Wegovy activates one. This fundamental difference means that milligram-for-milligram comparison is not scientifically valid — they simply aren't the same medication. Additionally, dose titration schedules differ: Mounjaro starts at 2.5 mg weekly for 4 weeks, whilst Wegovy starts at 0.25 mg weekly. Both require gradual escalation, and both require a prescription following clinical assessment by a UK-licensed 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.
Can I switch from Wegovy to Mounjaro at an equivalent dose?
No. Any switch between weight loss medications must be managed by your prescriber. You cannot simply switch to an "equivalent" dose — your prescriber will reassess your health, consider your previous response to Wegovy, and may start Mounjaro at a lower dose before escalating. This process requires a new clinical assessment.
Which medication causes more weight loss — Wegovy or Mounjaro?
Clinical trials suggest Mounjaro may produce slightly higher average weight loss (approximately 15–21% body weight) compared to Wegovy (approximately 15% body weight). However, individual results vary dramatically. Some people respond better to Wegovy, others to Mounjaro. Your prescriber will consider which is more suitable for your specific circumstances.
What's the difference between Mounjaro and Ozempic?
Both contain semaglutide, but Ozempic is approved for type 2 diabetes (doses up to 2 mg) — not for weight loss. Wegovy is the licensed weight management version (up to 2.4 mg). Using Ozempic for weight loss is off-label and not recommended in the UK. Always ask your prescriber which medication you're being prescribed.
How long does it take to reach the maximum dose on each medication?
Mounjaro typically reaches maximum dose (15 mg) in about 20 weeks of 4-week escalations. Wegovy reaches maximum dose (2.4 mg) in approximately 16 weeks of 4-week escalations. Both timelines assume you escalate at each step without remaining on a dose longer than needed.
Does MyWeightCheck have tools to help me track potential weight loss with either medication?
Yes. Our free GLP-1 weight loss calculator above allows you to estimate potential weight loss outcomes at different doses based on clinical trial data. You can also use our BMI calculator to track your starting BMI and our progress tracker to log your actual results once treatment begins.
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.