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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Mounjaro Weight Loss Injection in the UK
Mounjaro (tirzepatide) is a prescription-only weekly weight loss injection licensed in the UK for managing obesity and overweight. It's a GIP and GLP-1 receptor agonist — a dual-action medication that may help reduce appetite and support weight management alongside diet and exercise. Access in the UK is available through NHS specialist tier 3 weight management services or private online prescribing following clinical assessment. This guide explains NHS eligibility, how Mounjaro works, and your options for accessing this weekly weight loss injection in the UK.
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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.
NHS Eligibility and Access for Mounjaro
NHS eligibility criteria: You may access Mounjaro through the NHS if you have a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with at least one weight-related health condition such as type 2 diabetes, prediabetes, high blood pressure, or cardiovascular disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply — potentially from 27.5 kg/m² or above.
NHS route: Mounjaro is prescribed through specialist tier 3 weight management services, not standard GP prescription. You'll need referral from your GP to a local specialist service in your integrated care board (ICB). Clinical trials including SURMOUNT-1 showed participants on Mounjaro 15 mg lost an average of approximately 21% of body weight over 72 weeks, though individual results vary significantly. Treatment is always combined with reduced-calorie diet and increased physical activity.
- Specialist assessment required before prescription
- Regional availability varies — waiting lists can be lengthy
- Prescribed doses range from 2.5 mg to 15 mg weekly
- Not available for under-18s or pregnant individuals
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.
Private vs NHS Access Routes
NHS access: Longer waiting times (often months to years depending on your area), but treatment cost is covered by the NHS if approved through specialist services. Availability depends heavily on your local ICB's funding and capacity.
Private access: Available through GPhC-registered online pharmacies with UK-licensed prescribers — faster access without NHS referral, but you'll pay privately (costs vary by dose and provider). Either route requires a clinical assessment to confirm suitability.
Use our GLP-1 weight loss calculator to estimate potential outcomes at different doses, and our BMI calculator to check whether you may be eligible. Your GP or prescriber will give personalised advice based on your individual health profile and local NHS availability.
- 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 Mounjaro and how does it work for weight loss?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — it activates two natural hormone pathways that help regulate appetite and reduce cravings. Injected once weekly, it may help you feel fuller after smaller meals and support sustainable weight loss alongside diet and exercise. It's not insulin and works differently from other weight loss medications.
Am I eligible for Mounjaro on the NHS?
You may be eligible if you have a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with weight-related health conditions like diabetes or high blood pressure. Lower thresholds apply for South Asian and Black heritage adults. Ask your GP about referral to a specialist tier 3 weight management service in your area.
How much weight can I expect to lose on Mounjaro?
Clinical trials showed average weight loss of approximately 15–21% of body weight at the highest dose, but individual results vary significantly. Weight loss depends on your dose, adherence, diet changes, and physical activity. Your prescriber will monitor your progress and adjust treatment accordingly.
What are the common side effects of Mounjaro?
Very common side effects include nausea, diarrhoea, vomiting, and constipation — usually mild and temporary. Injection site reactions, fatigue, and dizziness may also occur. Most side effects reduce over time. Serious side effects are rare but seek urgent help if you experience severe stomach pain or signs of allergic reaction.
How do I access Mounjaro in the UK — NHS or private?
NHS access: referral from your GP to a specialist tier 3 weight management service (availability varies by region). Private access: consultation with a UK-licensed prescriber through a GPhC-registered pharmacy (faster, but you pay privately). Both routes require clinical assessment before prescription.
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.