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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Mounjaro vs Wegovy — Which Is Right for You in the UK?
Choosing between Mounjaro and Wegovy depends on several factors: how they work, their cost, how you access them, and your individual health needs. Both are prescription-only weight management injections licensed in the UK, but they differ in their mechanism, dosing schedule, and availability. This guide compares them across cost and access routes so you can have an informed conversation with your GP or prescriber.
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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.
How Mounjaro and Wegovy Work Differently
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist. It works on two natural hormone pathways simultaneously, which is why it's distinct from other weight loss injections. Wegovy (semaglutide) activates only the GLP-1 receptor agonist pathway. Both may help reduce appetite, support feeling fuller after smaller meals, and slow gastric emptying, but Mounjaro's dual mechanism may offer additional support for fat utilisation. In clinical trials, Mounjaro helped participants lose an average of 15–21% of body weight, whilst Wegovy showed average weight loss of around 15%. Individual results vary significantly, and both are most effective alongside a reduced-calorie diet and increased physical activity. Your prescriber will assess which mechanism suits your health profile best.
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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.
Cost, Access and Availability in the UK
NHS access: Both Mounjaro and Wegovy are available through NHS specialist tier 3 weight management services, but availability varies dramatically by region. You'll typically need a GP referral, and waiting lists can be several months to over a year in many areas. Private access: Both medications are available through private online consultations with UK-licensed prescribers, usually within days. Private costs range from approximately £120–£320 per month depending on the dose—Mounjaro doses range from 2.5 mg to 15 mg weekly, while Wegovy ranges from 0.25 mg to 2.4 mg weekly. Prices differ between providers, so it's worth comparing. An online clinical assessment is required before either medication is prescribed.
- 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.
Is Mounjaro cheaper than Wegovy in the UK?
Costs vary by provider and dose, but generally they're similar—both range from £120–£320 monthly on the private market. NHS access is free but involves longer waits. Your prescriber will help determine which is suitable based on your health profile, not just cost.
Can I get Mounjaro or Wegovy on the NHS without waiting months?
NHS access depends on your local Integrated Care Board's resources and waiting lists. Private routes are typically faster—often within days of a clinical assessment. Your GP can advise on both pathways available to you locally.
Which causes fewer side effects—Mounjaro or Wegovy?
Both have similar common side effects: nausea, diarrhoea, constipation, and stomach pain. Individual tolerance varies. Your prescriber can discuss which might suit you better based on your medical history and any previous medication experiences.
Do I need a prescription from my GP to get either medication privately?
No. Private online consultations are conducted by UK-licensed prescribers who assess your eligibility independently. Your GP doesn't need to be involved, though it's helpful to inform them you're considering weight loss treatment so they can monitor your progress.
Which medication causes weight loss faster—Mounjaro or Wegovy?
Clinical trials show Mounjaro and Wegovy produce similar average weight loss over 12–24 months, though Mounjaro's dual mechanism showed slightly higher averages. Both require patience—sustainable results typically take several months at the correct dose.
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.