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 — Cost and Access in the UK
Finding affordable GLP-1 weight loss medication in the UK involves understanding both NHS and private options. Mounjaro (tirzepatide) and Wegovy (semaglutide) are the most commonly prescribed weight loss injections, but costs, availability, and mechanisms differ. This guide breaks down pricing, access routes, and eligibility so you can make an informed decision with your prescriber about which option is right for your health needs and budget.
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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.
Mounjaro and Wegovy — How They Work and Cost Differently
Mounjaro is a dual GIP and GLP-1 receptor agonist — meaning it activates two natural hormone pathways to help regulate appetite and support weight loss. Wegovy is a GLP-1-only agonist with a single mechanism. Clinical trials showed Mounjaro users lost an average of 15–21% of body weight over 72 weeks, whilst Wegovy users lost approximately 15% on average — though individual results vary significantly.
Private pricing differs between providers. Mounjaro KwikPen typically costs £150–£220 per month depending on your dose, whilst Wegovy pens range from £129–£180 monthly. NHS access for both requires referral to specialist weight management services (tier 3), where availability and waiting times vary by region. Your prescriber will assess tirzepatide suitability based on your BMI, weight-related health conditions, and individual circumstances.
- Mounjaro doses: 2.5 mg to 15 mg once weekly
- Wegovy doses: 0.25 mg to 2.4 mg once weekly
- Both require prescription and clinical assessment
- Results vary — use our free GLP-1 weight loss calculator to estimate potential outcomes
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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
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Which Is Right for You? Prescriber Assessment Is Essential
The choice between Mounjaro and Wegovy is personal and depends on your health profile, eligibility, and prescriber guidance — not just cost. Some patients respond better to dual GIP+GLP-1 activation (Mounjaro), whilst others achieve excellent results with GLP-1-only (Wegovy). Both are prescription-only medicines requiring clinical assessment before dispensing.
If NHS access suits your timeline, your GP can refer you to a specialist weight management service — typically free on the NHS once approved, though waiting lists vary. For faster private access, licensed UK prescribers assess you via online consultation. Use our free BMI calculator above to check your starting point, then discuss options with a healthcare professional who can evaluate your individual suitability for 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.
Is Mounjaro cheaper than Wegovy in the UK?
Pricing varies by dose and provider. Mounjaro typically costs £150–£220/month privately; Wegovy ranges £129–£180/month. Exact cost depends on your dose tier — lower doses cost less. Both are free via NHS specialist services if approved, though availability and waiting times vary by region.
Can I get Mounjaro or Wegovy on the NHS?
Yes. NICE has approved both for NHS specialist weight management services (tier 3). Access requires GP referral and assessment by a specialist team. Eligibility criteria include BMI ≥30 (or ≥27.5 with weight-related health conditions for some groups). Regional availability and waiting lists vary significantly.
What's the difference between Mounjaro and Wegovy mechanisms?
Mounjaro (tirzepatide) is a dual GIP+GLP-1 agonist activating two hormone pathways. Wegovy (semaglutide) is a GLP-1-only agonist. The dual mechanism in Mounjaro may help some people lose more weight, but individual responses vary. Your prescriber will assess which suits you best.
Do I need a prescription for either medication?
Yes, both Mounjaro and Wegovy are prescription-only medicines in the UK. You cannot purchase them without a valid prescription from a UK-licensed prescriber. Private prescriptions are issued following an online clinical assessment; NHS prescriptions come through specialist services.
How long before I see results with either injection?
Clinical trials show weight loss typically becomes noticeable within 4–8 weeks, with progressive loss over 12–20 weeks as your dose increases. Results vary between individuals. Use our free weight loss calculator to see estimated projections at different doses based on clinical trial data.
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.