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 Wegovy To Mounjaro — UK Cost & Access Guide
If you're considering switching from Wegovy (semaglutide) to Mounjaro (tirzepatide), you'll want to understand dose equivalents, costs, and how to access both medications in the UK. While both are prescription-only weight loss injections, they work differently and have different pricing structures. This guide explains what you need to know about switching between these two GLP-1 and dual-action weight loss medications, whether you're accessing them privately or through NHS specialist services.
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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.
UK Private Prescription Costs For Wegovy And Mounjaro
Wegovy (semaglutide) typically costs between £130–£250 per month when prescribed privately in the UK, depending on your dose. The 2.4 mg maintenance dose is at the higher end of this range. Mounjaro (tirzepatide) usually ranges from £129–£320 per month, with costs varying based on dose — the 15 mg maximum dose costs more than lower starting doses.
- Wegovy costs: 0.25 mg–0.5 mg doses (£130–£180/month); 1 mg–1.7 mg doses (£180–£220/month); 2.4 mg dose (£220–£250/month)
- Mounjaro costs: 2.5 mg–5 mg doses (£129–£180/month); 7.5 mg–10 mg doses (£180–£240/month); 12.5 mg–15 mg doses (£240–£320/month)
Prices vary between GPhC-registered online pharmacies, and some offer subscription discounts. Always compare costs across providers before committing. Your GP may be able to advise whether either medication is available through NHS specialist weight management services in your area, though waiting lists can be several months in many regions.
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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 Versus Private Prescription Routes
NHS route: Both Wegovy and Mounjaro are NICE-approved for weight management through NHS specialist tier 3/4 weight management services, but access is very limited and varies significantly by region. You'll need a referral from your GP and face substantial waiting lists — often 6–12 months or longer depending on your local ICB (Integrated Care Board). NHS provision is free once approved.
Private route: You can access Mounjaro UK prescription or Wegovy privately by completing an online consultation with a UK-licensed prescriber through a GPhC-registered pharmacy. The assessment typically takes 24–48 hours. You'll need to confirm BMI eligibility (BMI ≥30, or ≥27 with weight-related health conditions) and answer health questions. A prescription is issued if you're clinically suitable, then the medication is delivered to your home. Use our free BMI calculator and GLP-1 weight loss calculator to understand your potential eligibility and projected outcomes with either medication.
Dose equivalence between Wegovy and Mounjaro: While there's no official conversion chart, approximate clinical equivalents are: Wegovy 0.5 mg ≈ Mounjaro 5 mg; Wegovy 1.7 mg ≈ Mounjaro 10 mg; Wegovy 2.4 mg ≈ Mounjaro 15 mg. However, tirzepatide (Mounjaro) is a dual GIP/GLP-1 agonist, while semaglutide (Wegovy) is GLP-1-only, so they are not direct equivalents. Any switch between medications must be managed by your prescriber — never stop one and start the other without guidance. Switching typically involves a gap of 1–2 weeks between stopping Wegovy and starting Mounjaro.
- 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.
What's the main difference between Wegovy and Mounjaro?
Wegovy (semaglutide) is a GLP-1 receptor agonist that signals fullness and slows digestion. Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist, activating two hormone pathways, which may provide stronger appetite suppression. Both are once-weekly injections. Clinical trials show Mounjaro may deliver slightly higher average weight loss, but individual results vary significantly.
How much does Wegovy cost in the UK on private prescription?
Wegovy private costs range from approximately £130–£250 per month depending on dose. The starting dose (0.25 mg) is cheaper; the full 2.4 mg dose costs around £220–£250 monthly. Prices vary between GPhC-registered online pharmacies. Some providers offer subscription discounts if you commit to ongoing treatment. Always compare costs before purchasing.
Can I get Mounjaro or Wegovy on the NHS in the UK?
Both are NICE-approved for NHS weight management services, but access is limited to specialist tier 3/4 services. You need a GP referral and face waiting lists of many months in most areas. Availability varies significantly by region. Private prescription is faster (24–48 hours) but costs £130–£320 monthly depending on medication and dose.
Is Mounjaro more expensive than Wegovy in the UK?
Generally, Mounjaro costs slightly more, especially at higher doses — up to £320/month at 15 mg versus Wegovy's £250/month at 2.4 mg. However, prices overlap at lower doses. Shop around: some private providers price them similarly. Your choice should depend on which medication your prescriber recommends, not just cost.
What happens if I switch from Wegovy to Mounjaro?
Your prescriber will typically advise a gap of 1–2 weeks between stopping Wegovy and starting Mounjaro to allow washout. You'll restart at a low Mounjaro dose (2.5 mg) and titrate up, even if you were on a high Wegovy dose. Never switch medications without medical guidance. A prescriber can advise whether switching is appropriate for your individual health.
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.