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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Is Mounjaro Safe in the UK? What You Need to Know
Mounjaro (tirzepatide) is a prescription-only weight management injection that is approved and considered safe for use in the UK when prescribed appropriately. Like all medications, it carries potential side effects, but these are generally manageable. This guide covers Mounjaro's safety profile, how to access it in the UK through both NHS and private routes, what it costs, and what the clinical evidence shows. Understanding your options helps you make an informed decision with your GP or prescriber.
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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.
How Safe Is Mounjaro? UK Safety Profile & Evidence
Mounjaro has been assessed and approved by the MHRA (Medicines and Healthcare products Regulatory Agency), the UK's medicines regulator. It carries a Black Triangle (▼) designation, which means it is subject to additional monitoring for safety. This is standard for newer medicines and does not indicate it is unsafe — it simply means the regulator is carefully tracking any new safety signals.
Safety in clinical trials: The SURMOUNT-1 trial involved over 2,600 adults and found tirzepatide to be effective for weight management. The most common side effects were gastrointestinal — nausea, diarrhoea, vomiting, and constipation — which typically improved over time as the body adjusted. Serious adverse events were rare.
When Mounjaro may not be suitable: It is not recommended for people under 18, those pregnant or breastfeeding, those with a personal or family history of medullary thyroid cancer, or those with multiple endocrine neoplasia type 2. Your prescriber will assess these factors during your clinical assessment.
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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.
How to Access Mounjaro in the UK: NHS vs Private Routes
NHS access: Mounjaro is approved by NICE for use within specialist tier 3 and tier 4 weight management services. You would need a GP referral to your local NHS specialist weight management service. However, availability varies significantly by region and waiting lists can be lengthy — sometimes many months.
Private access: You can obtain a prescription through a UK-licensed online prescriber following an online clinical assessment, without waiting for NHS referral. Once approved, your prescription is dispensed by a GPhC-registered pharmacy. Private prescriptions typically cost between £129 and £320 per month depending on your dose. Use our free GLP-1 weight loss calculator to estimate potential results at different doses before committing.
The online consultation process: When accessing Mounjaro privately, you complete a health questionnaire covering your medical history, current medications, allergies, and weight loss goals. A prescriber reviews this and may request additional information or blood pressure readings. If approved, you receive a prescription valid at participating pharmacies. The entire process typically takes 24–72 hours. Always ensure the prescriber is UK-licensed and the pharmacy is GPhC-registered.
What to expect after prescription: Your prescriber will guide you on injection technique, storage (refrigerated at 2–8°C), and titration schedule. You start at 2.5 mg once weekly and typically increase every 4 weeks. Regular check-ins with your prescriber are recommended to monitor progress and side effects.
- 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.
Is Mounjaro safe to use long-term in the UK?
Yes, Mounjaro is approved for long-term weight management. The clinical evidence supports ongoing use when monitored by a healthcare professional. Some people use it for extended periods; others use it for 12–24 months then stop. Your prescriber can discuss the right duration for your situation. Like all prescription medications, safety depends on proper medical supervision.
What are the common side effects of Mounjaro in the UK?
The most common side effects are gastrointestinal: nausea, diarrhoea, vomiting, and constipation. These typically occur in the first few weeks and often improve as your body adjusts. Less common side effects include headache, fatigue, and injection site reactions. Serious side effects are rare but can include pancreatitis (severe stomach pain). Always report persistent or serious symptoms to your prescriber immediately.
Why does Mounjaro have a Black Triangle symbol in the UK?
The Black Triangle (▼) symbol indicates that a medicine is subject to additional monitoring by the MHRA. This is normal for newer medications and means the regulator is carefully tracking safety data. It does not mean Mounjaro is unsafe — it is a standard monitoring system to catch any new safety signals early. The symbol may be removed once sufficient safety data accumulates.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs typically range from £129 to £320 per month depending on your dose. Starting doses (2.5 mg) are usually at the lower end; maximum doses (15 mg) at the higher end. Prices vary slightly between prescribers and pharmacies. Some providers offer package discounts if you pay upfront for multiple months. Check current pricing with your chosen prescriber or pharmacy for exact costs.
Can I get Mounjaro on the NHS in the UK?
Yes, Mounjaro is approved by NICE for NHS use through specialist tier 3 and 4 weight management services. Access is via GP referral to your local NHS service. However, availability and waiting times vary significantly by region (ICB). Some areas have waiting lists of several months. If you cannot access it through the NHS, private prescription is an alternative route available through licensed UK prescribers.
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.