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
Free tracker included with every download this week
Mounjaro vs Wegovy in the UK — Doses, Costs & Access
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight loss injections licensed in the UK, but they work differently and have different costs. This guide compares the two medications side-by-side so you understand the key differences, clinical evidence, and how to access each one. Neither medication is available as a discount code or promotion — costs depend on your dose and whether you're accessing through the NHS or private prescription. Your prescriber will assess which, if either, is suitable for you based on your individual health.
10,000+ calculations today · NHS-aligned thresholds · 100% free
Calculate Your BMI Instantly
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 Differ — Mechanism and Trial Evidence
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways simultaneously. In the SURMOUNT-1 clinical trial, participants taking 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. In the STEP-1 clinical trial, participants taking the maximum 2.4 mg dose lost an average of approximately 14.9% of their body weight over 68 weeks, also with diet and exercise support.
- Starting doses: Mounjaro begins at 2.5 mg; Wegovy at 0.25 mg
- Maximum doses: Mounjaro 15 mg weekly; Wegovy 2.4 mg weekly
- Injection frequency: Both are once-weekly injections
- Key difference: Mounjaro's dual mechanism may account for larger average weight loss in trials, though individual results vary significantly
Use our free GLP-1 weight loss calculator above to explore potential weight loss projections at different doses of either medication.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
Accessing Mounjaro and Wegovy in the UK — NHS vs Private Cost
NHS access: Both medications are approved by NICE for use within specialist tier 3 weight management services. You'll need a GP referral to an NHS weight management service in your region. Availability varies significantly by area, and waiting lists can be lengthy (several months to over a year in some areas).
Private access: Both are available through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber. Private costs typically range from £129–£320 per month depending on the dose you're prescribed. There are no official discount codes or promotions — cost varies by provider and dose level. A private prescriber will assess your eligibility based on your BMI, health history, and current medications before issuing a prescription. Neither medication is available over-the-counter.
- 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.
Which medication causes more weight loss, Mounjaro or Wegovy?
Clinical trials showed Mounjaro users lost approximately 20.9% body weight on average (at maximum dose), compared to approximately 14.9% with Wegovy. However, individual results vary significantly. Your prescriber will help determine which is suitable for you based on your health profile, not trial averages.
Can I get a discount code for Mounjaro or Wegovy in the UK?
No official discount codes exist for either prescription medication. Private costs range £129–£320/month depending on dose and provider. NHS access is free but requires specialist referral and varies by region. Always check directly with prescribers about pricing for your specific dose.
What's the difference between Mounjaro and Wegovy mechanisms?
Mounjaro is a dual GIP+GLP-1 agonist (two hormone pathways), while Wegovy is a GLP-1-only agonist (single pathway). This dual action in Mounjaro may contribute to larger average weight loss in clinical trials, though both work by reducing appetite and supporting fullness.
How long does each medication take to work?
Both require gradual dose increases over several weeks. Initial effects on appetite typically appear within 1–2 weeks, but significant weight loss usually takes 8–12 weeks to become noticeable. Full effects at maximum dose develop over 16–20 weeks.
Can I switch from Wegovy to Mounjaro or vice versa?
Switching is possible but must be managed by your prescriber. There's no official conversion chart — approximate equivalence is Wegovy 2.4 mg ≈ Mounjaro 10–15 mg, but dosing is individual. Your GP or private prescriber will guide any medication change.
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.