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 — Cost and Clinical Comparison
If you're looking for Mounjaro cheap online in the UK, you may also be considering Wegovy as an alternative. Both are prescription-only weight loss injections available through private prescribing services. Understanding the differences between these medications — including cost, how they work, and clinical trial results — helps you make an informed decision with your prescriber. Both require a clinical assessment before prescription, and individual suitability varies considerably.
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 Work — Key Differences
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways simultaneously. This dual mechanism may provide additional appetite suppression compared to GLP-1-only medications. In the SURMOUNT-1 clinical trial, participants on Mounjaro 15 mg lost an average of 20.9% of their body weight over 72 weeks.
Wegovy (semaglutide) is a GLP-1 receptor agonist only, activating a single hormone pathway. In the STEP-1 clinical trial, participants on Wegovy 2.4 mg lost an average of 14.9% of body weight over 68 weeks. Both medications are used alongside a reduced-calorie diet and increased physical activity — they are not standalone treatments.
- Mounjaro: dual mechanism, higher average weight loss in trials
- Wegovy: single mechanism, well-established long-term safety data
- Both: once-weekly injections, UK prescription-only
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.
Cost Comparison and Private Access in the UK
Private prescription costs for both medications vary by dose and provider, typically ranging from £129 to £320 per month. Mounjaro may sometimes appear cheaper at lower doses because the starting dose (2.5 mg) is lower than Wegovy's. However, as doses escalate, prices can become similar or overlap. Use our free GLP-1 weight loss calculator to understand dosing progression and discuss costs with your prescriber. Your GP can also refer you to NHS specialist weight management services if you meet eligibility criteria, though NHS availability varies significantly by region and waiting lists can be lengthy.
- 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 definitely cheaper than Wegovy online?
Not necessarily. While Mounjaro's starting dose may be lower-cost, final prices depend on your titrated dose and the provider. At higher doses (Mounjaro 15 mg vs Wegovy 2.4 mg), costs often converge or overlap. Always compare prices across GPhC-registered pharmacies and discuss options with your prescriber.
Which medication causes more weight loss — Mounjaro or Wegovy?
Clinical trials show Mounjaro produced higher average weight loss (20.9% vs 14.9%) in their respective studies. However, individual results vary significantly based on genetics, lifestyle, adherence, and other factors. Your prescriber will advise which suits your circumstances best.
How do I know if I'm eligible for Mounjaro or Wegovy?
Both require a BMI of 30 kg/m² or above, or 27 kg/m² with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea, cardiovascular disease). A licensed prescriber assesses your individual eligibility during consultation. Use our free BMI calculator to check your starting point.
Can I switch from Wegovy to Mounjaro or vice versa?
Yes, but any medication switch must be managed by your prescriber. There is no official conversion chart — dosing is individualised. Switching typically involves a washout period and gradual titration on the new medication.
What's the difference between Mounjaro and Ozempic?
Both contain semaglutide, but Ozempic is licensed for type 2 diabetes (up to 2 mg weekly) and Wegovy is licensed for weight management (up to 2.4 mg weekly). Mounjaro contains tirzepatide (different drug, dual mechanism). Using Ozempic for weight loss is off-label in the UK — Wegovy is the licensed weight management option.
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.