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 PIL — UK Prescribing Information
Mounjaro (tirzepatide) is a prescription-only weight management injection licensed in the UK for adults living with excess weight. The Patient Information Leaflet (PIL) contains essential safety and usage information that your prescriber will discuss with you. This guide explains how Mounjaro works, UK eligibility criteria, NHS access routes, and what the clinical evidence shows. Use our free BMI calculator and GLP-1 weight loss calculator to understand your personal context before speaking to your GP or a licensed prescriber.
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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.
How Mounjaro Works and UK Eligibility
Mounjaro is a dual GIP and GLP-1 receptor agonist — different from single-action medications like Wegovy (semaglutide). It activates two natural hormone pathways to help regulate appetite, reduce food cravings, and support feeling fuller after meals. The standard dose titration follows this schedule: 2.5 mg weekly for weeks 1–4, then increases to 5 mg, 7.5 mg, 10 mg, 12.5 mg, and up to 15 mg maximum, with at least 4 weeks at each dose.
NHS eligibility in the UK requires:
- BMI of 30 kg/m² or above, OR
- BMI of 27–29.9 kg/m² with a weight-related health condition (type 2 diabetes, high blood pressure, abnormal blood fats, sleep apnoea, or cardiovascular history)
- For South Asian, Chinese, Black African, and Black Caribbean adults: lower thresholds may apply (from BMI 27.5)
Access is through NHS tier 3 specialist weight management services, typically following GP referral. Regional availability varies significantly, and waiting lists can be lengthy.
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 in the UK
NHS route: Mounjaro is approved for use within NHS specialist tier 3/4 weight management services under NICE guidance. You'll need a GP referral to access these services. NHS prescribing costs nothing at the point of use, but availability depends on your local Integrated Care Board (ICB) and current waiting lists.
Private route: Available through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber. No GP referral needed. Costs vary (typically £129–£320 monthly depending on dose). Private access is faster but not NHS-subsidised. Either route requires a valid prescription and clinical assessment confirming you meet eligibility criteria.
- 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 does the Mounjaro PIL tell me about side effects?
The PIL lists nausea, diarrhoea, vomiting, constipation, and stomach pain as very common side effects. Common side effects include indigestion, acid reflux, injection site reactions, fatigue, and dizziness. Always read the full PIL before starting, and report any concerning symptoms to your prescriber immediately.
How does Mounjaro compare to Wegovy under NICE guidance?
Both are NICE-approved for weight management in UK adults. Mounjaro is a dual GIP+GLP-1 agonist; Wegovy is a single GLP-1 agonist. Clinical trials show Mounjaro may produce slightly higher average weight loss (~15–21% vs ~15% for Wegovy), but individual results vary significantly. Your prescriber will advise which is suitable for you.
Can I access Mounjaro through the NHS immediately?
No. NHS access requires a GP referral to a tier 3 specialist weight management service. Waiting times vary by region — some areas have waiting lists of many months. Private prescribing is typically faster. Check with your local ICB about current waiting times and eligibility criteria in your area.
What does Mounjaro dose titration mean?
Dose titration is the gradual increase of your Mounjaro dose over time. You start at 2.5 mg weekly and increase approximately every 4 weeks (to 5 mg, then 7.5 mg, 10 mg, 12.5 mg, 15 mg) until you reach the dose your prescriber recommends. This approach helps your body adjust and minimises side effects.
Does the PIL say anything about using Mounjaro with other medications?
Yes. Mounjaro may reduce the absorption of oral contraceptives and other oral medications. If you take oral contraceptives, use a barrier method or switch contraception for 4 weeks after starting and after each dose increase. Always inform your prescriber of all medications you take before starting Mounjaro.
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.