The UK's most complete GLP-1 guide
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- 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 — Finding Weight Loss Injections in the UK
If you're searching for where to access Mounjaro (tirzepatide) in the UK, you're likely considering your weight loss options. Both Mounjaro and Wegovy are prescription-only GLP-1 receptor agonist medications licensed for weight management in UK adults, but they work slightly differently and are accessed through different routes. This guide explains the clinical differences, trial data, and how to get either medication through the NHS or private prescription services. Individual suitability depends on your health profile — your GP or a licensed prescriber will assess which is appropriate 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.
Mounjaro and Wegovy — Mechanism and Trial Data Comparison
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways that regulate appetite and blood sugar. In the SURMOUNT-1 clinical trial, participants on the maximum 15 mg dose lost an average of 20.9% of their body weight over 72 weeks, alongside a reduced-calorie diet and increased physical activity.
Wegovy (semaglutide) is a single GLP-1 receptor agonist, activating only the GLP-1 pathway. In the STEP-1 trial, participants on the maximum 2.4 mg dose lost approximately 14.9% body weight over 68 weeks under similar lifestyle conditions.
- Mounjaro dosing: starts at 2.5 mg, escalates to maximum 15 mg once weekly
- Wegovy dosing: starts at 0.25 mg, escalates to maximum 2.4 mg once weekly
- Both require minimum 4 weeks on each dose before increasing
- Individual results vary significantly — trial averages do not predict personal outcomes
Both medications slow gastric emptying and help reduce appetite, but Mounjaro's dual mechanism may offer different efficacy. Your prescriber will assess which 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.
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Accessing Mounjaro or Wegovy in the UK — NHS vs Private Routes
Both Mounjaro and Wegovy are prescription-only medicines requiring a clinical assessment before supply. NHS access is through specialist tier 3 weight management services — your GP must refer you, and availability varies significantly by region. Waiting lists can extend several months to years in many areas.
Private access is available through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber. This route typically offers faster access without NHS referral, though costs apply. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses, and check your BMI using our BMI calculator to understand your eligibility baseline.
- Both require prescription and clinical assessment — neither is available over-the-counter
- Eligibility: BMI ≥30, or BMI 27–29.9 with weight-related health conditions
- Prescriber determines suitability based on your individual health history
- 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 is the main difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — it activates two hormone pathways. Wegovy (semaglutide) is a GLP-1 agonist only — it activates one pathway. This dual mechanism in Mounjaro may result in different appetite regulation and outcomes, though both support weight loss. Individual response varies.
Which caused more weight loss in clinical trials?
In their respective trials, Mounjaro participants (SURMOUNT-1) lost an average of 20.9% body weight at maximum dose, while Wegovy participants (STEP-1) lost approximately 14.9%. However, these are trial averages under controlled conditions. Real-world results vary based on diet, activity, adherence, and individual metabolism.
Can I get Mounjaro on the NHS in the UK?
Mounjaro is available through NHS specialist tier 3 weight management services, but you must be referred by your GP. Availability and waiting times vary significantly by region and local commissioning decisions. Private prescription routes typically offer faster access.
What dose does Mounjaro come in compared to Wegovy?
Mounjaro ranges from 2.5 mg to 15 mg weekly. Wegovy ranges from 0.25 mg to 2.4 mg weekly. Approximate equivalence suggests Mounjaro 5 mg ≈ Wegovy 0.5 mg, and Mounjaro 15 mg ≈ Wegovy 2.4 mg, but any switch between medications must be managed by your prescriber.
How do I know which injection is right for me?
Your GP or a licensed prescriber will assess your health history, current medications, contraindications, and preferences to determine suitability. Both are prescription-only and require clinical assessment. You cannot self-determine which is appropriate — a prescriber must make that decision based on your individual circumstances.
Ready to take control of your weight loss journey?
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