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 currently taking Mounjaro (tirzepatide) and considering switching to Wegovy (semaglutide), you'll want to understand the cost and access differences between these two GLP-1 weight loss injections. Both are prescription-only medications available in the UK through NHS specialist services or private online prescribing routes. The choice between them often comes down to eligibility, cost, and how your body responds to treatment. This guide explains the practical steps to move from Mounjaro to Wegovy and what you need to know about accessing each medication.
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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/mΒ²).
While BMI isn't a perfect measure β it doesn't account for muscle mass, bone density, or fat distribution β 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 β 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.
Cost And Access Routes For Wegovy In The UK
Wegovy (semaglutide 2.4 mg) is available in the UK through two main routes: NHS specialist weight management services and private online prescribing. On the NHS, Wegovy is funded in tier 3 and 4 specialist weight management centres, though access varies significantly by region and waiting lists can be lengthy. Private costs typically range from Β£129 to Β£280 per month depending on your dose and the online clinic you use. The starting dose (0.25 mg) is usually cheaper than the maximum maintenance dose (2.4 mg). If you're currently on Mounjaro through private prescribing, switching to Wegovy privately may involve a new online consultation, typically costing Β£40βΒ£100, though some clinics include this in the first month's medication cost. Your prescriber will assess whether Wegovy is suitable for you based on your current health, weight, and any changes since starting Mounjaro. Unlike Mounjaro's KwikPen, Wegovy comes in pre-filled auto-injection pens and uses the same once-weekly injection schedule, making the practical switch straightforward.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care β from a UK-regulated online pharmacy.
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 β 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 β completely free.
NHS Vs Private: Which Route Is Right For You?
NHS access requires referral to a specialist weight management service through your GP, but waiting times in many areas exceed 12 months. If you're already accessing Mounjaro via NHS specialist services and want to switch to Wegovy, discuss this directly with your weight management teamβthey can reassess and switch you if clinically appropriate. Private access is faster: you can complete an online consultation and receive a prescription within days if approved. This route costs more but offers flexibility and no waiting list. Your choice depends on budget, urgency, and whether you're currently in NHS or private treatment. If cost is a concern, discuss payment plans with private online clinicsβmany offer monthly instalments. Use our free GLP-1 weight loss calculator to compare potential outcomes at different doses of Wegovy versus Mounjaro, and our BMI calculator to track how your weight changes during any medication switch.
- 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 β 5mg β 7.5mg β 10mg β 12.5mg β 15mg
- GLP-1 receptor agonist
- Up to 15β17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg β 0.5mg β 1mg β 1.7mg β 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 | 15β22.5% | 12β17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20β32 weeks | 16β20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | Β£150βΒ£250/month | Β£150βΒ£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 β 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 directly from Mounjaro to Wegovy without a break?
This depends on your current dose and your prescriber's guidance. Some people switch immediately; others step down Mounjaro while starting Wegovy. Never stop Mounjaro or start a new medication without explicit prescriber instruction. Your online clinic will advise on the safest transition based on your health.
Will Wegovy cost more or less than Mounjaro on private prescription?
Costs are broadly similar, typically Β£129βΒ£280 monthly depending on dose. Starting doses (0.25β0.5 mg for Wegovy; 2.5 mg for Mounjaro) are cheaper than maximum doses (2.4 mg vs 15 mg). Request a quote from your chosen online clinic before switching.
How long does an online consultation for Wegovy typically take?
Most online consultations take 10β20 minutes. You'll complete a health questionnaire, speak with a prescriber by video or phone, and receive a decision within 24β48 hours if approved. A prescription is then sent to a GPhC-registered pharmacy.
If I'm on Mounjaro through the NHS, can I switch to Wegovy privately instead?
Yes. You can choose to access Wegovy privately at any time. Inform your NHS weight management team if you're moving to private care. There's no requirement to stay with NHS services once enrolled, though waiting times mean you may have already invested time in NHS referral.
What happens to my current Mounjaro prescription when I switch to Wegovy?
You'll need to discuss stopping Mounjaro with your prescriber before your Wegovy prescription begins. Do not stop either medication on your own. Your prescriber will advise the safest transition and may overlap doses for a week or step one down while starting the other, depending on your circumstances.
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.