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 5mg Mounjaro to Wegovy: Cost and Access in the UK
If you're currently on Mounjaro and considering switching to Wegovy, understanding the cost differences and access routes is essential. Both tirzepatide (Mounjaro) and semaglutide (Wegovy) are prescription-only GLP-1 receptor agonist medications available in the UK, but they work differently and have different pricing structures. This guide explains what you need to know about switching between them, whether you're accessing treatment through the NHS or privately, and what to expect during the transition process.
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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 Cost and Access Routes for Both Medications
Private prescription costs vary significantly depending on the dose and provider. Mounjaro at 5mg typically costs around £150–£200 per month privately, while Wegovy costs roughly £130–£180 per month depending on the supplier and dose stage. However, individual prices differ between providers, so it's worth comparing. Both are available through GPhC-registered online pharmacies following a clinical assessment by a UK-licensed prescriber. Access requires a consultation and prescription, not a simple swap. NHS access is much more limited — tirzepatide through NHS specialist weight management services is rare in most areas, and NHS Wegovy access is similarly restricted. Your GP can refer you to a tier 3 specialist service, but waiting lists are often long. Many people choose the private route specifically because of faster access and the ability to remain on their chosen medication without waiting months for NHS availability.
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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: Understanding Your Options
The NHS route requires referral from your GP to a specialist tier 3 weight management service. These services assess eligibility based on BMI (30 or above, or 27–29.9 with weight-related conditions) and may prescribe either Mounjaro or Wegovy depending on local formulary decisions and availability. However, not all regions fund these medications yet, and waiting lists can extend several months. The private route is faster: you complete an online consultation with a UK prescriber, answer health screening questions, receive a prescription if approved, and collect your medication from a GPhC-registered pharmacy within days. Use our free GLP-1 weight loss calculator above to explore projected outcomes at different doses, and discuss your choice with your prescriber based on your individual health profile.
- 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 typical monthly cost difference between Mounjaro and Wegovy privately in the UK?
Mounjaro at 5mg costs approximately £150–£200 monthly, while Wegovy at equivalent doses costs around £130–£180 monthly. Exact prices vary by provider and dose level. Switching from Mounjaro to Wegovy may result in modest savings, but individual pricing differs. Always check with multiple providers before deciding to switch for cost reasons alone.
Can I switch from Mounjaro to Wegovy on the NHS?
NHS switching between tirzepatide and semaglutide is determined by your specialist weight management service based on local formulary and your clinical response. You cannot simply request a switch — your prescriber assesses whether Wegovy is more appropriate. NHS availability of both medications is variable by region.
How long does it take to get Wegovy through a private online prescription in the UK?
Private online consultations typically take 24–48 hours for assessment. If approved, your prescription is sent to a GPhC-registered pharmacy, and medication usually arrives within 3–5 working days. NHS access through specialist services is considerably slower, often involving referral waits of several weeks or months.
What is the approximate Mounjaro to Wegovy dose conversion?
These are approximate clinical equivalences: 5mg Mounjaro is roughly equivalent to 0.5mg Wegovy, 10mg Mounjaro to 1.7mg Wegovy, and 15mg Mounjaro to 2.4mg Wegovy (maximum). However, direct conversion is not standardised — your prescriber decides the appropriate Wegovy starting dose based on your individual health, tolerability, and response history.
Do I need a new prescription to switch from Mounjaro to Wegovy?
Yes, switching medications requires a new prescription from your GP or a licensed prescriber. You cannot simply stop Mounjaro and start Wegovy without clinical guidance. Your prescriber will discuss the transition, appropriate dosing, and monitoring to ensure safe switching between these different GLP-1 medications.
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