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 2.5mg vs Wegovy — UK Cost and Comparison
Looking for the cheapest Mounjaro 2.5mg option in the UK? Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight management injections available through private prescribing, with costs varying by provider and dose. Understanding the differences between these two medications — including their mechanisms, clinical trial results, and eligibility criteria — can help you make an informed decision with your prescriber. Both require a clinical assessment before prescription.
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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 Trial Data and Mechanism Differences
Mounjaro is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways. Clinical trials (SURMOUNT-1) showed that participants on Mounjaro 5mg lost an average of approximately 15% of their body weight over 72 weeks, whilst those on the 15mg dose achieved around 20.9% average weight loss — though individual results vary significantly.
Wegovy is a GLP-1 receptor agonist only, activating a single hormone pathway. The STEP-1 clinical trial demonstrated average weight loss of approximately 14.9% body weight at 68 weeks on the maximum 2.4mg dose, alongside reduced-calorie diet and increased physical activity.
- Mounjaro starting dose: 2.5mg weekly; Wegovy starting dose: 0.25mg weekly
- Mounjaro maximum dose: 15mg weekly; Wegovy maximum dose: 2.4mg weekly
- Both injections are once-weekly with a KwikPen device
- Both may cause similar side effects including nausea, constipation, and diarrhoea
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.
Costs, Eligibility, and Prescriber Assessment
Private prescription costs in the UK vary significantly by provider and dose. Mounjaro 2.5mg starter doses typically range from £129–£180 per month, whilst Wegovy costs vary similarly depending on the dose level your prescriber recommends. Eligibility for both medications requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. A licensed prescriber will assess your individual health profile, medical history, and suitability during a clinical consultation. Your GP or a specialist can also discuss NHS tier 3 weight management services, though access and waiting times vary considerably across UK regions. Use our GLP-1 weight loss calculator to explore potential outcomes at different doses.
- 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 2.5mg cheaper than Wegovy in the UK?
Private prescription costs for both medications vary by provider and dose. Mounjaro 2.5mg starter doses and Wegovy's lower doses typically have comparable pricing between £129–£180 per month. Exact costs depend on the pharmacy and your prescriber's recommendation. Always compare providers and check if your prescriber offers different branded options.
Which causes fewer side effects — Mounjaro or Wegovy?
Both medications commonly cause nausea, constipation, and diarrhoea, especially during the first few weeks. Individual tolerance varies significantly. Mounjaro's dual mechanism may suit some people better, whilst others respond better to Wegovy's single GLP-1 pathway. Your prescriber will help determine which is more suitable based on your health history.
Can I switch from Wegovy to Mounjaro?
Yes, some people switch between medications, but this must be managed by your prescriber. Approximate dose equivalences exist (0.5mg Wegovy ≈ 5mg Mounjaro), but there is no official conversion chart. Any switch requires clinical guidance and assessment of your response to the previous medication.
Do I need to be referred to the NHS for Mounjaro or Wegovy?
Both are available privately following an online clinical assessment with a UK-licensed prescriber — no NHS referral needed. NHS access is through specialist tier 3 weight management services, but availability and waiting lists vary significantly by region. Your GP can discuss both pathways.
How do I know which medication is right for me?
A licensed prescriber will assess your eligibility, medical history, current medications, and individual health profile during consultation. Both require clinical assessment. Factors include your BMI, weight-related health conditions, and how you might respond to the dual GIP+GLP-1 mechanism (Mounjaro) versus GLP-1 only (Wegovy). Your prescriber will recommend the most suitable 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.