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 and Weight Management in the UK
Mounjaro (tirzepatide) is a prescription-only, once-weekly injectable medication licensed in the UK for weight management in adults. While public figures may discuss their own health choices, prescribing decisions in the UK are based on individual clinical assessment, NHS eligibility criteria, and whether specialist weight management services are available in your area. This guide explains how the NHS prescribing pathway works, what eligibility looks like, and how Mounjaro fits within UK weight management care.
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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 Pathway
In the UK, Mounjaro is available through NHS specialist weight management services (tier 3) following referral from your GP, though availability varies significantly by region. NHS eligibility for tirzepatide typically includes adults with a BMI of 30 kg/m² or above, or a BMI of 27–29.9 kg/m² with weight-related health conditions such as type 2 diabetes, cardiovascular disease, or high blood pressure. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds (27.5+) may apply due to higher health risks at lower weights.
NICE has approved tirzepatide for use within NHS services, though access depends on your local Integrated Care Board (ICB). Many areas have significant waiting lists for tier 3 services — sometimes months or years. Your GP can assess whether you meet criteria and refer you to your local specialist weight management team. Once referred, a multidisciplinary team including a dietitian, psychologist, and specialist doctor will conduct a full health assessment before tirzepatide or other medications are considered. The MyWeightCheck BMI calculator can help you check your starting BMI to understand where you fall relative to NHS thresholds.
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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 Access to Mounjaro in the UK
NHS route: Referral through your GP to tier 3 specialist weight management service. Free at point of use but subject to regional availability and waiting lists (sometimes very long). Includes full health monitoring and support from a multidisciplinary team.
Private route: Available through UK-licensed online prescribers following a remote clinical assessment. Not dependent on NHS waiting lists or geography. Costs vary by dose and provider (typically £130–£320/month). Requires your own responsibility for ongoing health monitoring.
Both routes require a prescription from a UK-licensed healthcare professional and a clinical assessment. Mounjaro is not available over-the-counter and individual suitability depends on your personal health history, medications, and weight-related conditions.
- 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 is Mounjaro and how does it work?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — a once-weekly injectable medication that activates two natural hormone pathways to help regulate appetite and support feeling fuller after meals. It may help reduce food cravings and is used alongside a reduced-calorie diet and increased physical activity.
Who is eligible for Mounjaro on the NHS in the UK?
NHS eligibility typically requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, cardiovascular disease, hypertension). South Asian, Chinese, Black African, and Black Caribbean adults may have lower thresholds. Referral through your GP to a tier 3 specialist weight management service is required.
How long are NHS waiting lists for Mounjaro?
Waiting times vary significantly by region and local Integrated Care Board (ICB). Some areas have waiting lists of several months to over a year. Contact your GP or local specialist weight management service for specific timeframes in your area.
What weight loss can I expect from Mounjaro?
Clinical trials showed that adults on Mounjaro lost an average of 15–21% of their body weight alongside diet and exercise changes — though individual results vary significantly. Your progress will depend on adherence to lifestyle changes, dose tolerance, and personal health factors.
Is Mounjaro available privately in the UK without NHS referral?
Yes. Mounjaro is available through UK-licensed online prescribers following a remote clinical assessment. This route bypasses NHS waiting lists but involves private costs (typically £130–£320/month depending on dose) and your own responsibility for health monitoring.
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.