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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Weight Loss Injections: Mounjaro in the UK
Mounjaro (tirzepatide) is a once-weekly weight loss injection licensed in the UK, but access and cost vary significantly depending on whether you pursue NHS or private routes. If you're considering this prescription weight loss injection for managing your weight, understanding your options—including eligibility, costs, and how to access treatment—is essential. This guide covers both pathways and what to expect from the clinical assessment process.
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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 Cost and Private Access in the UK
In the UK private sector, Mounjaro costs typically range from £129 to £320 per month depending on your dose and the provider. Costs are higher at starting doses (2.5 mg) and lower when calculated per week at maximum doses (15 mg). Private access is available through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber—you do not need an NHS referral. The assessment usually takes 10–15 minutes and covers your medical history, current medications, BMI, and weight-related health conditions. If approved, your prescription is sent directly to a pharmacy, and your first dose typically arrives within 3–5 working days. Our GLP-1 weight loss calculator can help you understand potential outcomes at different doses, which may inform your decision. You'll also need to factor in ongoing costs for the full treatment course, which typically lasts 12–24 months, plus the cost of sharps bins for safe needle disposal at home.
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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 Access vs Private: Which Route Is Right for You?
The NHS route is free if eligible, but access is limited to specialist tier 3 weight management services following a GP referral. Availability varies widely by region and ICB (Integrated Care Board)—some areas have waiting lists of 6–18 months. Your GP will assess whether you meet the criteria: typically a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea. The private route is faster (weeks, not months) and doesn't require NHS referral, but costs several hundred pounds monthly. Use our BMI calculator to check whether you might meet NHS eligibility criteria, then discuss your options with your GP. Some patients combine approaches—starting privately while waiting for NHS assessment, or vice versa.
- 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.
How much does Mounjaro cost per month in the UK?
Private Mounjaro costs typically £129–£320 per month depending on your dose. Starting dose (2.5 mg) is usually cheaper per month than maintenance doses, though your prescriber may gradually increase your dose over several weeks. Some private providers offer package pricing if you commit to multiple months upfront, which may offer slight savings.
Can I get Mounjaro free on the NHS in the UK?
Yes, if you meet eligibility criteria and are referred to a specialist weight management service (tier 3). However, NHS availability varies significantly by region. Many areas have long waiting lists. Your GP can advise whether you're eligible and how to access NHS services in your area, though some regions currently have limited availability.
How long does a clinical assessment take for private Mounjaro?
An online clinical assessment with a private prescriber typically takes 10–15 minutes. You'll be asked about your medical history, current medications, BMI, weight-related health conditions, and lifestyle. The prescriber reviews this information and decides whether Mounjaro is appropriate for you before issuing a prescription.
What's the difference between accessing Mounjaro via NHS and private prescription?
NHS access is free but involves referral to specialist services and may have waiting lists (weeks to months in many areas). Private access is faster (usually within days) but costs £129–£320 monthly. Both routes require a clinical assessment and prescription from a UK-licensed healthcare professional.
Do I need to see my GP before getting a private prescription for Mounjaro?
No—private online prescribers can assess you directly without NHS involvement. However, it's still wise to inform your GP that you're considering or using Mounjaro, especially if you take other medications. Your GP should be aware of any weight loss medication you're using for safety and continuity of care.
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.