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 Weight Loss Pen — NHS Access & Eligibility in the UK
Mounjaro (tirzepatide) is a prescription-only weekly weight loss injection that has been approved by NICE for use within NHS specialist weight management services. This guide explains NHS eligibility criteria, how the drug works, and the difference between accessing Mounjaro through the NHS versus private prescribing in the UK. Use our free BMI calculator above to check whether you might meet the eligibility threshold, and our GLP-1 weight loss calculator to estimate potential outcomes if prescribed.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Criteria for Mounjaro in the UK
Mounjaro is available on the NHS for adults who meet specific weight and health criteria:
- BMI of 30 kg/m² or above (obesity), OR
- BMI of 27–29.9 kg/m² with at least one weight-related health condition
- For South Asian, Chinese, Black African, or Black Caribbean adults, lower thresholds apply — eligibility may begin at BMI 27.5 or above
Weight-related conditions that may qualify include type 2 diabetes, prediabetes, high blood pressure, abnormal cholesterol, sleep apnoea, or a history of heart disease or stroke. Access is through NHS tier 3 specialist weight management services, not standard GP prescription. NICE has approved tirzepatide for use within these specialist services, though availability varies significantly by region and integrated care board (ICB).
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 Access for Mounjaro in the UK
NHS route: Referral from your GP to a tier 3 specialist weight management service. Assessment and prescription occur within specialist services. Many regions have substantial waiting lists (sometimes months to years). No prescription cost if eligible on NHS.
Private route: Online consultation with a UK-licensed prescriber, prescription issued if appropriate, dispensed by a GPhC-registered pharmacy. Available without NHS referral. Usually costs £129–£320 per month depending on dose. Results vary individually, and private prescribing also requires evidence-based clinical assessment.
- 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 does Mounjaro work as a weight loss injection?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist. It activates two hormone pathways that regulate appetite and food intake, helping you feel fuller sooner and reducing cravings. It also slows gastric emptying. These effects typically work alongside a reduced-calorie diet and increased physical activity for sustained results.
What weight loss results can I expect with Mounjaro on NHS?
Clinical trials showed average weight loss of approximately 15–21% of body weight over 72 weeks on Mounjaro, alongside diet and exercise. However, individual results vary significantly. Your NHS specialist team will discuss realistic expectations during your assessment. Use our GLP-1 weight loss calculator to see estimated projections.
What is the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP+GLP-1 agonist manufactured by Eli Lilly. Wegovy (semaglutide) is a GLP-1-only agonist made by Novo Nordisk. Both are once-weekly injections licensed for weight management in the UK. Mounjaro showed slightly higher average weight loss in trials, but both require prescription and clinical assessment.
Can I get Mounjaro on the NHS if my BMI is 27?
Yes, if your BMI is 27–29.9 and you have a weight-related health condition (diabetes, high blood pressure, sleep apnoea, or cardiovascular disease). For South Asian, Chinese, Black African, or Black Caribbean heritage, eligibility may start at BMI 27.5. Your GP can refer you to a tier 3 specialist service for assessment.
How long does it take to access Mounjaro through NHS specialist services?
Waiting times vary considerably by region and ICB. Some areas have waits of several months to over a year. Contact your local NHS weight management service or ask your GP for typical timescales in your area. Private prescribing is often faster (typically 1–2 weeks) but requires payment. Use our BMI calculator to check your starting point.
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.