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
Free tracker included with every download this week
Understanding Mounjara in the UK
Mounjara is not a recognised UK medication name — you may be looking for Mounjaro (tirzepatide), which is the prescription-only weight management injection licensed in the UK. Mounjaro is a dual GIP and GLP-1 receptor agonist approved by the MHRA for adults with obesity or overweight with weight-related health conditions. This guide provides UK-specific information about how Mounjaro works, NHS eligibility criteria, and how to access it through the NHS or private prescription. If you're exploring weight management options in the UK, understanding the correct medication name and UK health guidance is essential for finding the right support.
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.
How Mounjaro Works and UK Access Routes
Mounjaro (tirzepatide) is the correct UK brand name for this prescription-only weight management injection. It activates two natural hormone pathways — GIP and GLP-1 — which help regulate appetite and support feeling fuller after meals. In clinical trials, Mounjaro helped participants lose an average of 15–21% of their body weight, though individual results vary significantly. In the UK, you can access Mounjaro through two routes: NHS specialist tier 3 weight management services (requiring GP referral, though availability and waiting times vary by region) or private online prescribing (following a clinical assessment with a UK-licensed prescriber). Check your BMI using our free BMI calculator above to understand whether you may meet eligibility criteria, which typically includes a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease.
- Once-weekly injection (pre-filled KwikPen device)
- Doses range from 2.5 mg to 15 mg
- MHRA-approved and subject to additional monitoring
- Must be used alongside reduced-calorie diet and physical activity
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 Guidance and Practical Next Steps
The NHS has approved tirzepatide (Mounjaro) for use within specialist weight management services, though access varies significantly across UK regions due to funding and availability. NICE guidelines support its use for eligible adults. If you're considering Mounjaro, start by speaking with your GP about weight management options in your area — they can assess your individual health needs and discuss whether NHS specialist referral or private prescribing is appropriate. Use our free weight loss calculator to explore potential outcomes at different doses, and our weight converter to track your progress in the measurements you're most comfortable with. Always ensure any prescription is issued by a UK-licensed prescriber following a proper 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.
Is Mounjara the same as Mounjaro?
Mounjara is not a recognised UK medication name. You're likely looking for Mounjaro, which is the correct UK brand name for tirzepatide. Mounjaro is a prescription-only weight management injection licensed by the MHRA in the UK. Always check the correct spelling with your prescriber or pharmacist.
How do I access Mounjaro on the NHS in the UK?
NHS access to Mounjaro is through specialist tier 3 weight management services, which requires a GP referral. Availability varies by region — ask your GP whether your local ICB (Integrated Care Board) commissions this treatment. Waiting lists can be lengthy. Private prescribing is also available without NHS referral.
What weight loss can I expect from Mounjaro?
Clinical trials showed Mounjaro helped participants lose an average of 15–21% of their body weight over 72 weeks, alongside a reduced-calorie diet and increased physical activity. However, individual results vary significantly. Use our GLP-1 weight loss calculator to see projected outcomes based on current research.
Who is eligible for Mounjaro in the UK?
UK eligibility typically includes adults with a BMI of 30 or above, or 27 or above with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea, cardiovascular disease). Lower BMI thresholds apply for people of South Asian, Chinese, Black African, or Black Caribbean heritage. Check with your GP or prescriber for personalised advice.
What are the main side effects of Mounjaro in the UK?
Common side effects include nausea, diarrhoea, vomiting, constipation, and stomach pain — these are usually most noticeable when starting or increasing doses. Serious side effects are rare but can include severe stomach pain (possible pancreatitis) or gallbladder problems. Your prescriber will discuss all risks and benefits during your clinical assessment.
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.