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 1 Mg Wegovy Equivalent to Mounjaro in the UK?
When comparing Wegovy (semaglutide) and Mounjaro (tirzepatide), understanding dose equivalence is important — though no official conversion exists between these two different medications. Approximately, 1 mg Wegovy may be considered roughly equivalent to 5 mg Mounjaro in terms of weight loss effect, though clinical outcomes vary significantly between individuals. Both are prescription-only GLP-1-type weight loss injections licensed in the UK, but they work differently: Wegovy is a single GLP-1 receptor agonist, while Mounjaro is a dual GIP and GLP-1 agonist. Your GP or prescriber will assess which is more suitable for your individual health needs.
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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.
Understanding Dose Equivalence and NHS Prescribing in the UK
Approximate dose equivalence: While no formal conversion chart exists between Wegovy and Mounjaro, clinical guidance suggests 1 mg Wegovy may be comparable to approximately 5 mg Mounjaro, and 2.4 mg Wegovy (maximum Wegovy dose) may relate to around 15 mg Mounjaro (maximum Mounjaro dose). However, these are rough approximations only — individual response varies. Wegovy reaches its maximum therapeutic dose of 2.4 mg per week over 17 weeks, whereas Mounjaro escalates more gradually from 2.5 mg to 15 mg. Both medications are prescription-only and available in the UK through NHS specialist tier 3 weight management services or private online prescribers following clinical assessment.
- Wegovy: GLP-1 agonist only (single hormone pathway)
- Mounjaro: GIP + GLP-1 agonist (dual hormone pathways)
- Different mechanisms mean direct dose comparison is not straightforward
- Both require prescription and medical supervision
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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.
NHS Access and Choosing Between Wegovy and Mounjaro
In the UK, NHS access to both medications is through tier 3 specialist weight management services, though availability varies significantly by region and waiting lists are often lengthy. NICE approves both tirzepatide (Mounjaro) and semaglutide (Wegovy) for eligible adults with a BMI of 30 or above, or 27–29.9 with weight-related comorbidities. Your prescriber will assess which medication is appropriate based on your individual health profile, medical history, and response to treatment. Switching between medications can be done under clinical guidance, but any change requires reassessment and a new prescription. Private access is also available through GPhC-registered online prescribers without NHS referral, offering faster access but at personal cost.
- 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 1 mg Wegovy actually equivalent to 5 mg Mounjaro?
Approximately, yes — but this is a rough clinical equivalence, not an official conversion. The two medications work via different mechanisms (single vs dual hormone pathways), so direct comparison is limited. Individual weight loss varies regardless of dose. Only a prescriber can advise which dose or medication is suitable for you.
Can I switch from Wegovy to Mounjaro on the NHS?
Yes, you can switch between medications under NHS specialist care, but it requires reassessment and a new prescription from your prescriber. You cannot simply substitute one for the other at home. The switch is managed by your tier 3 weight management service or private prescriber, depending on where you access treatment.
What's the difference between Wegovy and Mounjaro for weight loss?
Wegovy is a GLP-1 agonist (single hormone pathway). Mounjaro is a GIP/GLP-1 agonist (dual pathways). Clinical trials show both help with weight loss — Wegovy by approximately 15% and Mounjaro by 15–21% on average — but individual results vary. Some people respond better to one than the other. Your prescriber will recommend based on your health profile.
How do I get Wegovy or Mounjaro on the NHS in the UK?
Request referral to your local tier 3 specialist weight management service through your GP. You must have a BMI of 30+ or 27+ with weight-related health conditions. NHS provision varies by region and waiting times can be several months to over a year. Private online prescribing offers faster access but requires personal payment.
Are Wegovy and Mounjaro always taken weekly?
Yes, both are once-weekly injections. Wegovy uses a pre-filled auto-injection pen, and Mounjaro uses a KwikPen device. Neither requires daily injections like some older GLP-1 medications (Saxenda). Both are self-administered at home, though initial injections are sometimes done at clinic with staff supervision.
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.