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 Comparison in the UK
If you're considering Mounjaro (tirzepatide) for weight management in the UK, understanding how it compares to other options and how to access it through the NHS is essential. Mounjaro is a prescription-only GIP and GLP-1 receptor agonist that works differently to other weight loss injections available in the UK. This guide explains NHS eligibility criteria, how Mounjaro is prescribed through specialist services, and how it compares to alternatives like Wegovy in the UK context. Use our free BMI calculator above to check your starting point, then explore your options with your GP or a licensed prescriber.
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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.
NHS Eligibility and Mounjaro Access in the UK
In the UK, Mounjaro is approved for weight management in adults through NICE guidance and is available via NHS specialist tier 3 weight management services. Eligibility criteria include a BMI of 30 kg/m² or above, or a BMI of 27–29.9 with weight-related comorbidities such as type 2 diabetes, hypertension, or cardiovascular disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds may apply (BMI 27.5 and above).
NHS access requires referral from your GP to a specialist tier 3 service, though availability and waiting times vary significantly by region. The Mounjaro KwikPen is supplied through NHS pharmacy once initiated by the specialist service. Dosing follows a titration schedule, starting at 2.5 mg weekly and escalating to a maintenance dose based on response and tolerance.
- NHS route: referral-based, cost-free at point of use, variable waiting times
- Private route: online consultation with UK prescriber, faster access, costs typically £129–£320 monthly depending on dose
- Dose titration: minimum 4 weeks at each dose level before increasing
- Maximum dose: 15 mg once weekly
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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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Mounjaro vs Wegovy: Key Differences in the UK
Mounjaro (tirzepatide) and Wegovy (semaglutide) are both GLP-1-based weight loss injections licensed in the UK, but they work via different mechanisms. Mounjaro is a dual GIP and GLP-1 agonist, activating two hormone pathways, while Wegovy activates GLP-1 only. Clinical trial data shows Mounjaro achieved average weight loss of approximately 15–21% of body weight, whilst Wegovy showed around 14.9% average loss in UK trials—though individual results vary significantly.
Eligibility criteria are similar for both medications, but Mounjaro typically requires a higher starting dose (2.5 mg) compared to Wegovy's 0.25 mg. Both are prescribed through NHS specialist services or private online prescribing. Our GLP-1 weight loss calculator can help you estimate potential outcomes at different doses. Neither medication is a replacement for diet and physical activity—both work best alongside lifestyle changes.
- 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 available on the NHS in the UK?
Yes. Mounjaro is NICE-approved and available through NHS tier 3 specialist weight management services. Access requires a GP referral and clinical assessment by the specialist service. Availability and waiting times vary by region. Private access is also available through licensed UK prescribers without NHS referral.
What is the difference between Mounjaro and Wegovy?
Mounjaro is a dual GIP and GLP-1 receptor agonist, whilst Wegovy is a GLP-1 agonist only. Clinical trials show Mounjaro achieved slightly higher average weight loss (15–21% vs 14.9%), but both require prescription and clinical assessment. Eligibility criteria are similar in the UK.
What is the starting dose of Mounjaro in the UK?
The starting dose is 2.5 mg once weekly via KwikPen injection. Doses escalate every 4 weeks (5 mg, 7.5 mg, 10 mg, 12.5 mg, 15 mg maximum) based on individual response and tolerance. Your prescriber will monitor progress and adjust accordingly.
How long does it take to see weight loss results with Mounjaro?
Weight loss typically begins within 2–4 weeks, but most significant changes occur after 12–16 weeks as doses escalate. Individual results vary considerably. Our progress tracker can help you log changes over time and identify trends in your personal weight loss journey.
Can I switch from Wegovy to Mounjaro on the NHS?
Switching between medications must be managed by your prescriber. Whilst approximate dose equivalences exist (e.g., Wegovy 1.7 mg ≈ Mounjaro 10 mg), any change requires clinical assessment and guidance from your NHS specialist or private prescriber to ensure safe transition.
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.