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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What Is Monjiro? UK Health Information
You may have heard the term "Monjiro" mentioned in discussions about weight management, but this spelling is not the standard medical name used in the UK. The prescription medication you're likely looking for is Mounjaro (tirzepatide), a once-weekly injectable licensed for weight management in UK adults. Understanding the correct name, how it works, and whether it might be suitable for you requires accurate NHS guidance. MyWeightCheck provides free health calculators and information to help you make informed decisions about your weight and health. This guide clarifies the terminology and explains what UK adults need to know about weight management options available through the NHS and private prescribing.
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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.
The Correct Name and UK Context
The term "Monjiro" appears to be a misspelling or variation of Mounjaro (pronounced "mun-JAR-oh"), the brand name for tirzepatide. Mounjaro is a prescription-only weight management injection licensed by the MHRA in the UK. It works as a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways that help regulate appetite and support feeling fuller after meals. Mounjaro is administered as a once-weekly injection and comes in doses ranging from 2.5 mg to 15 mg. In the UK, it is available through NHS specialist weight management services (tier 3/4) and also through private online prescribing following a clinical assessment. Clinical trials showed that participants taking Mounjaro lost an average of 15–21% of their body weight when combined with a reduced-calorie diet and increased physical activity — though individual results vary considerably. Eligibility typically requires 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. Always consult your GP or a licensed prescriber to discuss whether this medication is appropriate for your individual health situation.
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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.
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UK Access, NHS Guidance, and Next Steps
In the UK, accessing Mounjaro depends on your route: NHS access is through referral to a specialist weight management service, though waiting times and availability vary significantly by region. Private access is available through GPhC-registered online pharmacies following a clinical assessment by a UK-licensed prescriber, without requiring an NHS referral. Whichever route you choose, a prescriber will assess your BMI, health history, and any existing medications to determine suitability. Use our free BMI calculator above to check your current BMI and see where you fall on the NHS health weight scale. Your GP can also provide guidance on local NHS weight management services and discuss whether prescription options are right for you. Remember that weight management is most effective when medication is combined with lifestyle changes including a reduced-calorie diet and regular physical activity.
- 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 "Monjiro" a real medication?
"Monjiro" is not the standard spelling used in the UK. The correct name is Mounjaro (tirzepatide), a prescription-only weight management injection licensed by the MHRA. If you've seen "Monjiro" mentioned online, it may be a misspelling or variation. Always check the correct name with your GP or prescriber to avoid confusion.
How do I access Mounjaro in the UK?
Mounjaro is available through two main routes: NHS specialist weight management services (requires GP referral, availability varies by region) and private online prescribing (requires clinical assessment by a licensed prescriber). Both routes require a prescription and an assessment of your eligibility based on BMI and health conditions.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Mounjaro has a single mechanism of action. Clinical trials showed Mounjaro achieved average weight loss of 15–21%, compared to approximately 15% for Wegovy. Results vary individually, and either medication requires prescription and clinical assessment.
How much weight can I expect to lose with Mounjaro?
Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks when Mounjaro was combined with diet and exercise changes. However, individual results vary significantly — some people lose more, others less. Weight loss depends on your starting weight, dose, adherence, diet, and activity level. Use our free GLP-1 weight loss calculator above for a personalised estimate.
Do I need to see my GP before taking Mounjaro?
Yes. Mounjaro is prescription-only and requires a clinical assessment before being prescribed. Whether through NHS services or private prescribing, a licensed healthcare professional must evaluate your health history, BMI, medications, and weight-related health conditions to ensure it is safe and appropriate for you.
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