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, Discounts & Clinical Differences
Searching for a Mounjaro discount code for a second order? Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight management injections available in the UK, but they work differently and have different cost structures. Understanding the clinical differences between these GLP-1 and dual GIP/GLP-1 medications can help you and your prescriber decide which is most suitable for your situation. This guide compares both medications factually, covering mechanism, trial data, eligibility, and practical access routes 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.
Clinical Mechanism & Trial Data: Key Differences
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two separate hormone pathways to regulate appetite and blood sugar. The SURMOUNT-1 clinical trial showed participants on the maximum 15 mg dose lost an average of approximately 20.9% of their body weight over 72 weeks, alongside a reduced-calorie diet and increased physical activity. Wegovy (semaglutide) is a GLP-1-only receptor agonist, activating a single hormone pathway. The STEP-1 trial showed average weight loss of approximately 14.9% body weight at 68 weeks on the maximum 2.4 mg dose under similar conditions. Individual results vary significantly, and these are clinical trial averages, not assures. Both medications slow gastric emptying and reduce appetite, but Mounjaro's dual mechanism may provide additional metabolic support for some patients. Your prescriber will assess which mechanism may suit your individual 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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Eligibility, Access & Cost Routes in the UK
Both Mounjaro and Wegovy require a UK prescription following a clinical assessment. NHS access is through tier 3 specialist weight management services (referral from your GP), with significant waiting times and regional variation. Private access is available through GPhC-registered online pharmacies following an online consultation. Private costs vary by dose and provider—typically £129–£320 per month depending on which medication and dose tier you're on. Discount codes and second-order offers vary by provider; costs are not negotiable on NHS routes. Your prescriber (NHS or private) will assess your BMI, health conditions, and medication interactions to determine which medication is clinically appropriate for you. Use our free GLP-1 weight loss calculator to estimate potential outcomes at different doses, and our BMI calculator to understand your current health context.
- 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.
Does Mounjaro have better results than Wegovy?
Clinical trial data shows higher average weight loss with Mounjaro (20.9% at maximum dose) versus Wegovy (14.9%), but individual results vary significantly. Trial conditions included diet and exercise changes. Your prescriber will assess which medication suits your health profile, not which had higher trial averages. Both are prescription-only and require clinical suitability assessment.
Can I switch from Wegovy to Mounjaro to get a discount code?
Switching between medications should only be done under prescriber guidance—not to obtain discounts. If you're already prescribed one medication, your GP or prescriber can discuss whether switching is clinically appropriate for your situation. Any medication switch should be based on health outcomes, not cost alone.
What's the difference between GLP-1 only and GIP+GLP-1?
Wegovy activates the GLP-1 hormone pathway only. Mounjaro activates both GIP and GLP-1 pathways (dual agonist). The dual mechanism in Mounjaro may provide additional appetite regulation and metabolic effects, which clinical trials suggest correlates with higher average weight loss. Your prescriber can discuss which mechanism aligns with your health needs.
Are Mounjaro and Wegovy available on the NHS in the UK?
Yes, both are NHS-approved for weight management through specialist tier 3 services. Access requires GP referral to your local weight management service. Availability and waiting times vary significantly by region (ICB). Your GP can advise on NHS access in your area.
How long does a Mounjaro or Wegovy KwikPen last?
Each pre-filled pen contains 4 once-weekly doses (4 weeks of treatment). On the NHS, prescriptions are issued based on your licensed dose. Privately, costs are per dose or per pen. Discount codes sometimes reduce second-order costs; ask your provider about available offers.
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.