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 on NHS Wales vs Wegovy — Availability and Differences
If you're in Wales and considering weight loss medication, you may be wondering whether Mounjaro or Wegovy is available on the NHS and how they compare. Both tirzepatide (Mounjaro) and semaglutide (Wegovy) are prescription-only weight management injections licensed in the UK, but access through NHS Wales varies by health board, and availability differs significantly between the two medications. Understanding the key differences in mechanism, clinical trial data, and NHS access in Wales can help you have an informed conversation with your GP about which option might be suitable for you.
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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 vs Wegovy — Key Mechanism and Trial Data Differences
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways. Clinical trials (SURMOUNT-1) showed participants lost an average of 15–21% of their body weight over 72 weeks at various doses. In comparison, Wegovy (semaglutide) is a single GLP-1 receptor agonist, and trial data (STEP-1) demonstrated average weight loss of approximately 15% of body weight.
- Mounjaro: Once-weekly injection, dual mechanism, doses range from 2.5 mg to 15 mg, may offer slightly higher average weight loss in trials
- Wegovy: Once-weekly injection, single GLP-1 mechanism, maximum dose 2.4 mg, well-established safety profile
Both are used alongside a reduced-calorie diet and increased physical activity. Individual results vary significantly — trial averages do not predict personal outcomes. Your prescriber will assess which mechanism may suit your health profile better. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses.
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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 Wales Access and How to Get Prescribed Either Medication
Access to both Mounjaro and Wegovy through NHS Wales is limited and varies significantly by health board. Most NHS trusts in Wales route weight loss medication prescriptions through specialist tier 3 weight management services, not standard GP prescriptions. Waiting lists can be lengthy, and approval criteria are strict — typically requiring a BMI of 30 or above (or 27+ with weight-related health conditions like type 2 diabetes or cardiovascular disease).
Many people in Wales access these medications privately through GPhC-registered online prescribing services, which assess your eligibility following a clinical consultation. Private prescriptions cost between £129–£320 per month depending on dose. Your GP can discuss both NHS and private routes with you. Use our free BMI calculator to determine whether you may meet eligibility thresholds before contacting your healthcare provider.
- 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 available on NHS Wales?
Mounjaro (tirzepatide) is NICE-approved for NHS use, but NHS Wales access is limited and varies by health board. It is typically available only through specialist tier 3 weight management services, not standard GP prescription. Eligibility requires BMI ≥30 or BMI 27–29.9 with weight-related health conditions. Waiting lists are often lengthy. Private access is available without NHS referral.
Is Wegovy available on NHS Wales?
Wegovy (semaglutide) is also NICE-approved and available through NHS Wales specialist weight management services under similar eligibility criteria. However, NHS availability is limited and varies by health board. Private prescriptions are readily available and do not require NHS referral.
What's the main difference between Mounjaro and Wegovy mechanisms?
Mounjaro is a dual GIP and GLP-1 receptor agonist (activates two hormone pathways), while Wegovy is a single GLP-1 agonist. This dual mechanism in Mounjaro may explain slightly higher average weight loss in clinical trials, though individual results vary considerably. Your prescriber will determine which is more suitable for you.
What were the clinical trial weight loss results?
Mounjaro (SURMOUNT trial) showed average weight loss of 15–21% of body weight. Wegovy (STEP trial) showed average weight loss of approximately 15%. Both results were achieved alongside reduced-calorie diet and increased physical activity. Individual outcomes vary significantly — these are trial averages, not assures.
How do I get Mounjaro or Wegovy in Wales?
Through NHS: speak to your GP about referral to your local specialist weight management service (tier 3). Through private: consultation with a UK-licensed prescriber via a GPhC-registered online pharmacy. Private access is faster but costs £129–£320 monthly depending on dose. Your GP can discuss both options.
Ready to take control of your weight loss journey?
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