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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NHS Weight Loss Injections: Mounjaro in the UK
Mounjaro (tirzepatide) is a prescription weight loss injection now available through NHS specialist services in the UK following NICE approval. If you're considering this weekly weight loss injection, understanding how NHS access works, eligibility criteria, and the tier 3 specialist pathway is essential. This guide explains the current NHS position on Mounjaro, how it compares to private access, and what you need to know about the prescribing process in the UK health system.
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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.
NHS Eligibility and the Tier 3 Specialist Pathway
NICE has approved tirzepatide (Mounjaro) for use within NHS specialist weight management services in England, Scotland, Wales, and Northern Ireland. Access is through tier 3 specialist services, not standard GP prescription. You'll typically need a GP referral to a local weight management service, which assesses you against NHS eligibility criteria.
NHS eligibility for Mounjaro:
- BMI of 30 kg/m² or above, OR
- BMI of 27–29.9 kg/m² with at least one weight-related health condition (type 2 diabetes, prediabetes, high blood pressure, sleep apnoea, or cardiovascular disease)
- For South Asian, Chinese, Black African, or Black Caribbean adults, lower BMI thresholds apply (27.5 kg/m² and above)
Clinical trials showed that Mounjaro helped participants lose an average of 15–21% of their body weight when combined with dietary changes and increased physical activity. Individual results vary significantly. You can calculate your current BMI using our free BMI calculator to determine your starting point.
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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 Mounjaro Access in the UK
The NHS route offers access to Mounjaro at no cost to you but involves referral to tier 3 services and potential waiting lists, which vary significantly by region and integrated care board (ICB). Some areas have waiting lists of several months or longer. The private route offers faster access through online consultations with UK-licensed prescribers, but costs approximately £150–£320 per month depending on dose and provider. Both routes require a clinical assessment; the NHS assessment is through your local weight management service, whilst private access involves an online clinical questionnaire. If your GP referral is rejected or waiting times are very long, private access may be an alternative worth considering alongside your GP.
- 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.
Can I get Mounjaro free on the NHS in the UK?
Yes, NICE has approved Mounjaro for NHS specialist weight management services. However, you'll need a GP referral to your local tier 3 weight management service, and you must meet NHS eligibility criteria. Availability and waiting times vary significantly by region.
What is the tier 3 specialist pathway for NHS Mounjaro?
Tier 3 is NHS specialist multidisciplinary weight management. You're referred by your GP to your local tier 3 service, undergo a full clinical assessment, and if approved, Mounjaro is prescribed and managed by the specialist team alongside dietary support and behaviour change programmes.
How long are NHS waiting lists for Mounjaro in the UK?
Waiting times vary by region and ICB. Some areas have relatively short waits (weeks to a few months), whilst others have waiting lists exceeding 12 months. Contact your local ICB or weight management service for specific timescales in your area.
Is Mounjaro the same as the weekly weight loss injection available privately?
Mounjaro is the brand name for tirzepatide. It's the same medication whether accessed via NHS or privately. The key difference is cost (free on NHS, paid privately) and route (NHS via GP referral to tier 3; private via online prescriber). Our GLP-1 weight loss calculator can help you estimate potential outcomes at different doses.
What if I'm rejected for NHS Mounjaro or the waiting list is too long?
If your GP referral is rejected or waiting times are unacceptable, you have the option to explore private prescribing through a UK-licensed online prescriber, which bypasses NHS waiting lists. However, this involves paying privately. Discuss all options with your GP first to understand your NHS position.
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.