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
How Does Monjaro Work in the UK?
Monjaro is a prescription-only weekly weight loss injection containing tirzepatide, a dual GIP and GLP-1 receptor agonist that works by activating two natural hormone pathways in your body. Unlike older GLP-1 medications, Monjaro's dual mechanism helps regulate appetite, reduce cravings, and support feeling fuller after smaller meals. If you're considering Monjaro or want to understand your options, it's important to know how to access it in the UK and what costs are involved—whether through the NHS or private prescription routes.
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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 Monjaro Works: The Mechanism Behind the Injection
Monjaro contains tirzepatide, which activates both GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1) receptor pathways. This dual action is what distinguishes Monjaro from single-mechanism weight loss injections. When injected once weekly via the KwikPen device, tirzepatide signals to your brain that you're full, reduces food cravings, and slows how quickly food leaves your stomach—helping you eat less naturally without feeling deprived.
The medication works alongside your own body's appetite regulation systems. Clinical trials showed that on average, people using Monjaro lost between 15% and 20.9% of their body weight over 72 weeks, though individual results vary significantly. Doses start at 2.5mg and increase gradually up to a maximum of 15mg weekly, with your prescriber adjusting based on your response and tolerance.
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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.
UK Cost and Access: NHS vs Private Routes
NHS Access: Monjaro is available through specialist tier 3 weight management services, but access varies dramatically by region. You'll need a GP referral and may face waiting lists of several months to years depending on your local Integrated Care Board. NHS availability depends on regional funding and clinical need assessment.
Private Access: Many UK adults access Monjaro through private online prescribing following a clinical consultation with a UK-licensed prescriber. Once approved, prescriptions are dispensed by GPhC-registered pharmacies. Costs range from approximately £150–£320 per month depending on your current dose. Private access is faster but requires payment. Use our GLP-1 weight loss calculator to explore potential outcomes and understand if this option suits your needs.
- 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's the difference between Monjaro and other weight loss injections?
Monjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways instead of one. This dual mechanism may offer greater appetite suppression than single-action medications like Wegovy. Clinical trials showed slightly higher average weight loss with Monjaro, though individual results vary. The choice depends on your personal health profile and what your prescriber recommends.
How long does it take to see results with Monjaro?
Most people begin noticing reduced appetite and changes in food preferences within the first 2–4 weeks. Measurable weight loss typically becomes apparent after 4–8 weeks. However, Monjaro works best alongside a reduced-calorie diet and increased physical activity. Results vary between individuals, and some people respond more quickly than others.
Can I get Monjaro through the NHS?
Yes, Monjaro is available via NHS specialist weight management services (tier 3). However, you'll need a GP referral and must meet eligibility criteria (BMI 30+ or 27+ with weight-related health conditions). NHS availability depends on your regional Integrated Care Board and current capacity. Waiting times vary from months to years in many areas.
What does Monjaro cost privately in the UK?
Private prescriptions for Monjaro typically cost £150–£320 per month depending on your dose. Starting doses (2.5–5mg) are generally at the lower end, while maintenance doses (10–15mg) cost more. Some online prescribing services offer package discounts if you commit to longer-term treatment. Always check with individual providers for their exact pricing.
Do I need to do anything else while taking Monjaro?
Monjaro works best alongside lifestyle changes. The NHS and clinical trials emphasise combining medication with a reduced-calorie diet and regular physical activity. Your GP or prescriber will discuss realistic dietary targets and exercise recommendations. Track your progress using our free progress tracker to monitor weight loss and how you're feeling over time. ```
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.