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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Wegovy vs Mounjaro — Dose Comparison and UK Access
If you're considering GLP-1 weight loss injections in the UK, you've likely heard of both Wegovy (semaglutide) and Mounjaro (tirzepatide). While both are prescription-only weight management medications, they work differently, come in different dose ranges, and have different costs and access routes. This guide compares the two side-by-side so you can understand your options and what to expect from either NHS or private prescription in the UK.
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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.
Dose Ranges and Starting Points — What's the Difference?
Wegovy (semaglutide) starts at a lower dose and escalates gradually over 16 weeks. The starting dose is 0.25 mg once weekly, increasing through 0.5 mg, 1 mg, and 1.7 mg, reaching a maximum of 2.4 mg per week. This slower titration helps your body adjust and minimises nausea.
Mounjaro (tirzepatide) begins at 2.5 mg once weekly, with doses escalating to 5 mg, 7.5 mg, 10 mg, 12.5 mg, and finally 15 mg as the maximum. Mounjaro is a dual GIP and GLP-1 agonist — a different mechanism from Wegovy's single GLP-1 action — which may explain why clinical trials showed slightly higher average weight loss (approximately 15–21% body weight compared to Wegovy's approximately 15%).
Both require a minimum of 4 weeks at each dose before escalating. Individual results vary significantly, and some people reach their target weight at lower doses without needing to titrate further. Use our GLP-1 weight loss calculator above to explore potential outcomes at different dose levels.
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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.
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NHS Access vs Private Cost — How to Get Wegovy or Mounjaro in the UK
NHS Route: Both medications are approved by NICE for NHS specialist weight management services (tier 3 and 4). However, NHS access is not automatic — you must be referred by your GP to a specialist weight management service, which can involve waiting lists of months or even years depending on your region. Availability varies significantly by integrated care board (ICB). Prescriptions issued by the NHS are free once approved.
Private Route: Both Wegovy and Mounjaro are available through GPhC-registered online pharmacies following a digital consultation with a UK-licensed prescriber. Private cost ranges from approximately £129–£320 per month depending on your dose and provider. Higher doses cost more. An online clinical assessment is required before a prescription is issued — this is not a shortcut but a genuine medical evaluation to confirm suitability.
Your GP or prescriber will assess eligibility based on your BMI, health conditions, and individual circumstances. Calculate your BMI using our free BMI calculator above to check where you sit relative to NHS thresholds.
- 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 doses?
Wegovy starts much lower (0.25 mg) and titrates slowly to a maximum of 2.4 mg over 16 weeks. Mounjaro starts at 2.5 mg and goes up to 15 mg. Mounjaro is a dual GIP/GLP-1 agonist while Wegovy is GLP-1 only, which may explain differing weight loss outcomes between individuals. Both require at least 4 weeks at each dose.
How much does Wegovy cost on the NHS in the UK?
Wegovy is free on the NHS once prescribed through a specialist weight management service. However, NHS access requires a GP referral and can involve significant waiting times. Availability depends on your local ICB. Not all areas have active prescribing programmes, so check with your GP about local access.
What's the private cost of Mounjaro or Wegovy in the UK?
Private costs range from approximately £129–£320 per month depending on dose and provider. Lower doses (starting doses) are cheaper; maximum doses are more expensive. You'll also need to pay for an online clinical assessment before a prescription is issued, typically £30–£50. Always use a GPhC-registered pharmacy.
Can I switch from Wegovy to Mounjaro mid-treatment?
Potentially yes, but only under prescriber guidance. There's no official conversion chart, but approximate equivalences exist (e.g. Wegovy 2.4 mg ≈ Mounjaro 15 mg). Any switch must be managed by your prescriber, who will assess whether it's appropriate for you and adjust doses carefully to avoid adverse effects.
How do I access Mounjaro or Wegovy privately in the UK?
Book an online consultation with a UK-licensed prescriber through a GPhC-registered pharmacy or online clinic. You'll answer health questions, provide measurements (height, weight), and the prescriber will assess your eligibility based on BMI and health conditions. If approved, a prescription is issued and dispensed by the same service. The whole process typically takes 2–7 days.
Ready to take control of your weight loss journey?
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