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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Switching from Mounjaro to Wegovy in the UK
If you're considering switching from Mounjaro (tirzepatide) to Wegovy (semaglutide 2.4 mg), understanding the costs and access routes in the UK is essential. Both are prescription-only weight management injections with different mechanisms — Mounjaro is a dual GIP and GLP-1 agonist, while Wegovy is a GLP-1 agonist only. Your eligibility, costs, and waiting times will depend on whether you access treatment through the NHS or privately. This guide explains both routes, typical costs, and what to expect when switching between these medications.
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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.
Wegovy Cost and Access in the UK
Private prescription costs for Wegovy in the UK typically range from £129 to £320 per month depending on your dose and the prescribing provider. The starting dose (0.25 mg) costs less than the maximum dose (2.4 mg), which usually costs around £250–£320 monthly. Unlike Mounjaro, Wegovy requires daily injections (though the pen design makes this straightforward), while Mounjaro is once-weekly.
NHS access to Wegovy is available through specialist tier 3 weight management services following referral from your GP. However, availability varies significantly across NHS regions, and waiting lists can extend from several months to over a year in many areas. Some NHS services have now approved both Mounjaro and Wegovy — your GP can advise on local availability.
- Private costs: £129–£320/month depending on dose
- NHS access: through specialist referral (free, but waiting lists vary)
- Prescription required for both routes
- Clinical assessment needed before prescribing
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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 vs Private Routes: Which is Right for You?
The NHS route is free but involves a GP referral to a specialist weight management service and often significant waiting times. The private route is faster — you can access treatment within days following an online clinical assessment — but requires payment. Using our free GLP-1 weight loss calculator can help you estimate potential results with Wegovy at different doses, which may help inform your decision about cost versus expected outcomes.
When switching from Mounjaro to Wegovy, prescribers typically use approximate dose equivalence: Mounjaro 5 mg ≈ Wegovy 0.5 mg, Mounjaro 10 mg ≈ Wegovy 1.7 mg, and Mounjaro 15 mg ≈ Wegovy 2.4 mg. However, any switch must be managed by your prescriber — these are clinical recommendations, not automatic conversions.
- 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.
How much does Wegovy cost on private prescription in the UK?
Private Wegovy costs typically range from £129–£320 per month depending on your dose. Starting doses cost less; the maximum dose (2.4 mg) usually costs £250–£320 monthly. Prices vary slightly between prescribing providers, so it's worth comparing before committing.
Can I get Wegovy free on the NHS?
Yes, Wegovy is available through NHS specialist weight management services following GP referral. Access is free but availability varies significantly by region. Many areas have long waiting lists (months to over a year). Contact your GP to check local availability and waiting times.
What's the approximate dose conversion from Mounjaro to Wegovy?
Mounjaro 5 mg ≈ Wegovy 0.5 mg, Mounjaro 10 mg ≈ Wegovy 1.7 mg, and Mounjaro 15 mg ≈ Wegovy 2.4 mg. These are approximate clinical equivalences only — your prescriber will determine the appropriate starting dose for your switch based on your individual health and response.
How long does it take to access Wegovy privately?
Private Wegovy access is typically faster than NHS. After an online clinical assessment (usually completed within 24–48 hours), a prescription can be issued if you're clinically suitable. You may receive treatment within days, compared to NHS waiting lists of several months.
Why might I switch from Mounjaro to Wegovy?
Reasons to switch include personal preference, cost considerations, side effect management, or clinical recommendation. Mounjaro is dual-action (GIP + GLP-1); Wegovy is GLP-1 only. Some people respond better to one mechanism than the other. Your prescriber will advise if switching is appropriate for you.
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.