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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Monjero for Weight Loss: UK Prescription Information
Monjero (tirzepatide) is a prescription-only weight management injection available in the UK for eligible adults. It works by activating two natural hormone pathways—GIP and GLP-1—to help regulate appetite and support feeling fuller after smaller meals. Like other weight loss injections in the UK, Monjero is used alongside lifestyle changes including reduced-calorie diet and increased physical activity. This guide explains how it works, who may be eligible, and how to access it through NHS weight loss services or private prescription routes. Check your BMI using our free BMI calculator above to see whether you might meet initial eligibility criteria.
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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.
UK-Licensed Weight Loss Medications and Eligibility
Three prescription weight loss injections are currently licensed in the UK for weight management: Monjero (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). All three are GLP-1 medications, though Monjero is a dual GIP and GLP-1 receptor agonist, making it unique. Clinical evidence shows that these medications may help eligible adults achieve significant weight loss when combined with lifestyle changes.
UK eligibility criteria: Adults with a BMI of 30 kg/m² or above, or BMI 27–29.9 with at least one weight-related health condition, may be eligible. Weight-related conditions include type 2 diabetes, prediabetes, high blood pressure, abnormal blood fats, sleep apnoea, or cardiovascular disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply (from BMI 27.5 or above). Your GP can assess whether you meet criteria for prescription weight loss in the UK.
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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 access: Monjero and other weight loss injections are available through NHS specialist tier 3 and tier 4 weight management services. You'll need a GP referral and assessment by a specialist team. Availability varies significantly by region, and waiting lists can be lengthy in some areas.
Private access: Prescription weight loss medication is available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber. This route doesn't require NHS referral and is often faster, though costs apply (typically £129–£320 per month depending on dose). Either way, use our GLP-1 weight loss calculator above to explore potential weight loss projections at different doses, and speak with your GP about which route suits you best.
- 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 is Monjero and how does it work for weight loss?
Monjero (tirzepatide) is a once-weekly injectable prescription medication that activates two natural hormone pathways—GIP and GLP-1—to help reduce appetite, support feeling fuller after meals, and regulate food cravings. It's licensed in the UK for weight management in eligible adults and is used alongside reduced-calorie diet and physical activity.
Who is eligible for Monjero in the UK?
Adults with a BMI of 30 or above, or BMI 27–29.9 with a weight-related health condition (such as type 2 diabetes, high blood pressure, or sleep apnoea), may be eligible. Lower thresholds apply for people of South Asian, Chinese, Black African, or Black Caribbean heritage. Your GP can assess your individual eligibility.
How can I access Monjero in the UK—NHS or private?
On the NHS, Monjero is available through specialist weight management services after a GP referral and assessment. Privately, you can access it through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber. Private access is often faster but involves costs. Both routes require a valid prescription from a licensed healthcare professional.
How much weight can I expect to lose with Monjero?
Clinical trials showed that on average, people using Monjero lost approximately 15–21% of their body weight over 72 weeks, alongside reduced-calorie diet and physical activity. Individual results vary significantly. Use our weight loss calculator above to estimate potential outcomes for you based on current weight and dose.
What are the main side effects of Monjero?
Common side effects include nausea, diarrhoea, vomiting, constipation, and stomach pain, particularly when starting or increasing doses. These often improve over time. Serious side effects are rare but can include severe stomach pain (possible pancreatitis) or gallbladder problems. Always discuss side effect risks with your prescriber before starting.
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.