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 Support with Mounjaro in the UK
Mounjaro (tirzepatide) is now available through the NHS for weight support in eligible UK adults. NICE has approved this prescription-only injection as part of specialist weight management services. Whether you're considering NHS access or exploring private options, understanding how Mounjaro works within the UK health system is essential. This guide covers eligibility, how the NHS prescribes it, and what the clinical evidence shows. Use our free BMI calculator above to check your starting point, and our GLP-1 weight loss calculator to explore potential outcomes.
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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 Tier 3 Weight Management Services
The NHS provides Mounjaro through tier 3 specialist weight management services, typically accessed via GP referral. You may be eligible if you have a BMI of 30 or above, or a BMI of 27–29.9 with at least one weight-related health condition such as type 2 diabetes, prediabetes, high blood pressure, or sleep apnoea.
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, NHS guidance recognises lower thresholds—eligibility may start at BMI 27.5 or above. NHS access is subject to regional variation; waiting times for tier 3 services differ significantly across England, Scotland, Wales, and Northern Ireland. When prescribed by the NHS, Mounjaro is supplied as a weekly KwikPen injection, with doses starting at 2.5 mg and titrated up to a maximum of 15 mg. Clinical trials showed that on average, participants lost approximately 15–21% of their body weight, though individual results vary considerably.
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.
NHS vs Private Routes in the UK
NHS route: Free at point of use through tier 3 services, but involves GP referral and potential waiting lists. Availability depends on your local Integrated Care Board (ICB) funding and commissioning. Some regions offer Mounjaro more readily than others.
Private route: Available through GPhC-registered online prescribing services following an online clinical assessment. No referral needed, faster access, but requires out-of-pocket payment (typically £150–£300+ per dose depending on strength). Both routes require a prescription from a UK-licensed prescriber. Whichever route you choose, Mounjaro is always prescribed alongside lifestyle changes—reduced-calorie diet and increased physical activity. Track your progress using our free progress tracker.
- 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.
Am I eligible for Mounjaro on the NHS?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions. Lower thresholds apply if you're of South Asian, Chinese, or Black heritage. Your GP can refer you to tier 3 specialist services for assessment. Use our free BMI calculator to check your current BMI.
What is NICE's position on Mounjaro for weight management?
NICE has approved tirzepatide (Mounjaro) for use in specialist weight management services in the UK. It is recommended as an option for adults with obesity or overweight with weight-related conditions, alongside a reduced-calorie diet and physical activity.
What does the clinical evidence show about Mounjaro weight loss?
The SURMOUNT-1 trial showed average weight loss of 15–21% of body weight over 72 weeks at the highest dose (15 mg), alongside diet and exercise. Results varied significantly between individuals. Mounjaro is a GIP and GLP-1 receptor agonist—a dual mechanism injection given once weekly.
How long is the NHS waiting list for Mounjaro?
Waiting times vary by region and ICB. Some areas have shorter waits; others may have waiting lists of several months to over a year. Contact your local tier 3 weight management service for current timelines in your area.
Can I switch between the NHS and private Mounjaro prescriptions?
Yes, but continuity must be managed carefully. If you start privately and later access NHS services, your tier 3 team will need to take over prescribing. Conversely, if you leave NHS services, you may transition to private supply. Always inform your prescriber of any change.
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.