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 The Difference Between Wegovy And Mounjaro?
Both Wegovy (semaglutide) and Mounjaro (tirzepatide) are prescription-only weight management injections available in the UK, but they work differently, cost differently, and have different access routes. Wegovy is a GLP-1 receptor agonist, whilst Mounjaro is a dual GIP and GLP-1 agonist — meaning Mounjaro targets two hormone pathways rather than one. Understanding these differences, plus the cost and access routes in the UK, helps you and your GP make an informed choice about which might be right for you.
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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.
Cost And Availability In The UK: NHS Vs Private
NHS access: Both medications are approved by NICE for NHS use within specialist tier 3 weight management services, but availability varies significantly by region and waiting lists can be months or years in many areas. Not all NHS integrated care boards (ICBs) fund both medications equally — some prioritise one over the other.
Private prescription costs: Private costs range from approximately £129 to £320 per month depending on dose and the private prescriber. Mounjaro typically costs between £150 and £280 per month for doses ranging from 2.5mg to 15mg per week. Wegovy typically costs between £129 and £250 per month for doses from 0.25mg to 2.4mg per week. Costs vary between providers and may increase with dose escalation. Most private prescribers offer repeat prescriptions through GPhC-registered pharmacies without requiring new consultations each month, though some charge a monthly consultation fee.
- Both require an initial clinical assessment (NHS or private)
- Private online consultations typically cost £50–£150 for initial assessment
- Repeat prescriptions are often cheaper than initial consultations
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — 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 — 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.
How To Access Mounjaro And Wegovy: The NHS And Private Routes
NHS route: Ask your GP for a referral to your local specialist weight management service (tier 3). You'll be assessed by a multidisciplinary team, and if eligible, a prescription will be issued. Waiting times vary by region — some areas have 6–12 month waits, others longer.
Private online route: Complete an online health questionnaire with a UK-licensed prescriber (GMC-registered doctor), attend a video or telephone consultation, and if approved, receive a prescription to send to a GPhC-registered pharmacy for dispensing. This typically takes 3–7 days from start to delivery. Both routes require you to have a BMI of 30 or above, or 27–29.9 with weight-related health conditions. Use our free GLP-1 weight loss calculator to estimate potential weight loss outcomes at different doses, and our BMI calculator to confirm your eligibility before starting either medication.
- 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.
Which is more effective, Wegovy or Mounjaro?
Clinical trials suggest Mounjaro may produce slightly greater average weight loss (up to 21% body weight) compared to Wegovy (around 15%), but individual results vary significantly. The "best" option depends on your health profile, medical history, and personal response — a prescriber will assess which suits you.
Can I switch from Mounjaro to Wegovy on the NHS?
Yes, you can discuss switching with your specialist NHS weight management team, though some areas may have specific protocols. Any switch should be managed by your prescriber — there is no official conversion formula, so a new assessment is typically needed.
Why does Mounjaro cost more than Wegovy in some places?
Mounjaro's higher cost reflects its dual-action mechanism (targeting two hormone pathways rather than one), which may also result in greater average weight loss. However, prices vary between private prescribers, so it's worth comparing options.
How long does it take to get Mounjaro or Wegovy privately?
From initial online consultation to receiving your first injection usually takes 3–7 days. Initial assessment can be completed within 24–48 hours with many providers. NHS timelines are much longer — typically 6–12 months or more depending on your region.
Do I need a prescription for both Mounjaro and Wegovy in the UK?
Yes, both are prescription-only medicines. You cannot buy either over the counter or online without a valid UK prescription from a GMC-registered doctor. Always ensure you're using a GPhC-registered pharmacy to ensure safety and authenticity.
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.