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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Cheapest Mounjaro Injections — Cost & Eligibility in the UK
Finding the most affordable weight loss injection in the UK depends on where you access treatment and which medication suits your individual health needs. Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are available in the UK, but pricing varies significantly between NHS and private routes. This guide explains the costs, how they compare, and what determines which injection might be most suitable and cost-effective for you personally. Your GP or a licensed prescriber will assess your eligibility based on your BMI and overall health, not price alone. Use our free BMI calculator above to check where you stand, then explore your options below.
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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.
Mounjaro vs Wegovy — Cost & Clinical Trial Data
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist manufactured by Eli Lilly. In the SURMOUNT-1 clinical trial, participants on 15mg achieved average weight loss of approximately 20.9% of body weight over 72 weeks, alongside diet and exercise changes.
Wegovy (semaglutide) is a GLP-1 receptor agonist only, manufactured by Novo Nordisk. In the STEP-1 trial, participants on 2.4mg achieved average weight loss of approximately 14.9% of body weight over 68 weeks, also with lifestyle support.
Key differences affecting cost and suitability:
- Mounjaro: starting dose 2.5mg, maximum 15mg (7 dose escalations)
- Wegovy: starting dose 0.25mg, maximum 2.4mg (5 dose escalations)
- Both are once-weekly injections (KwikPen or auto-injector pens)
- Mounjaro dose titration typically takes 20+ weeks; Wegovy typically 16+ weeks
- Individual responses vary significantly — clinical trial averages do not predict personal outcomes
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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.
NHS vs Private Costs — Eligibility & Access
NHS access: Mounjaro is now approved by NICE for specialist tier 3/4 weight management services. You'll need referral from your GP and assessment by a specialist team. NHS prescription costs approximately £11.90 per item once dispensed (or free if eligible for exemptions). However, waiting lists in many areas are very long (months to years in some regions).
Private access: Available through GPhC-registered online pharmacies following clinical assessment. Costs typically range from £129–£320 per month depending on dose. Faster access than NHS but no subsidisation. Both routes require a valid prescription from a UK-licensed prescriber — pricing is set by individual private providers, not a central tariff.
Your prescriber will assess which medication is appropriate for your health profile, not which is cheapest. Use our GLP-1 weight loss calculator to understand potential outcomes at different doses before discussing options with your GP or prescriber.
- 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.
What's the difference between Mounjaro and Wegovy?
Mounjaro is a dual GIP + GLP-1 agonist; Wegovy is GLP-1 only. Mounjaro showed approximately 20.9% average weight loss in trials; Wegovy showed approximately 14.9%. Both require prescription and clinical assessment. Your prescriber will recommend the most suitable based on your health, not cost.
Can I get Mounjaro on the NHS for weight loss?
Yes, Mounjaro (tirzepatide) is now approved by NICE for specialist NHS weight management services. You need referral from your GP and assessment by a tier 3/4 specialist team. NHS prescription costs £11.90 per item once dispensed. Waiting lists vary by region and can be lengthy.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs vary by provider and dose, typically ranging from £129–£320 per month. This is not a fixed tariff — different GPhC-registered pharmacies set different prices. Always check current pricing directly with your chosen provider before committing.
Which weight loss injection is cheapest overall?
NHS costs are lower (£11.90 per item) if you can access specialist services, but waiting lists can be months or years. Privately, costs vary. The "cheapest" option isn't always the most suitable — your prescriber will recommend based on your medical history, BMI, and health conditions, not price.
How do I know if I'm eligible for either Mounjaro or Wegovy?
Both require BMI ≥30, or BMI 27–29.9 with weight-related health conditions (diabetes, high blood pressure, sleep apnoea, cardiovascular disease). South Asian, Chinese, Black African, and Black Caribbean adults may qualify at lower BMI. Use our free BMI calculator above, then discuss eligibility with your GP.
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.