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 Mounjaro Means: Complete UK Weight Loss Guide
Mounjaro is a prescription-only weight management injection that contains tirzepatide, a dual GIP and GLP-1 receptor agonist developed by Eli Lilly. It's licensed in the UK for adults with obesity or overweight with weight-related health conditions. Unlike single-mechanism medications like Wegovy (semaglutide), Mounjaro activates two natural hormone pathways simultaneously, which may help regulate appetite and support weight loss alongside diet and exercise. Access in the UK is available through NHS specialist weight management services or private online prescription services following clinical assessment.
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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 Mounjaro Works and What It Means for Weight Management
Mounjaro means you're using a dual GIP and GLP-1 receptor agonist — this is what sets it apart from other weight loss injections available in the UK. The medication activates two natural hormone pathways: GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1). Together, these mechanisms may help reduce appetite, support feeling fuller after smaller meals, and assist with fat utilisation. Clinical trials showed that participants using Mounjaro lost an average of 15–21% of their body weight over 72 weeks, though individual results vary significantly.
Mounjaro is administered as a once-weekly KwikPen injection. Starting doses begin at 2.5 mg, with escalation to a maximum of 15 mg over several weeks. The medication slows how quickly food leaves your stomach and helps regulate blood sugar levels. It's important to understand that Mounjaro is not insulin — it's a hormone-mimicking therapy designed specifically for weight management. Results are most effective when combined with a reduced-calorie diet and increased physical activity.
- Dual mechanism: activates both GIP and GLP-1 pathways
- Once-weekly injection using a KwikPen device
- Dosage range: 2.5 mg to 15 mg weekly
- Average weight loss in trials: 15–21% body weight
- Most effective alongside lifestyle changes
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.
Mounjaro Cost, Access, and NHS vs Private Routes in the UK
NHS access to Mounjaro is through NICE-approved specialist tier 3/4 weight management services. You'll typically need a GP referral, but availability and waiting times vary significantly by region — some areas have waiting lists of several months. NHS funding follows strict eligibility criteria: BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea.
Private prescription access is available without NHS referral. An online consultation with a UK-licensed prescriber costs approximately £50–£100, and Mounjaro itself typically costs £129–£320 per month depending on your dose. Private access is faster — often available within days rather than months. Both routes require clinical assessment to confirm suitability. Whichever route you choose, use our free BMI calculator above to check your eligibility criteria, and our GLP-1 weight loss calculator to project potential outcomes at different doses.
- NHS: free but regional availability varies; can involve months of waiting
- Private: faster access (days); costs £50–£100 consultation plus £129–£320/month medication
- Both require clinical assessment and prescription
- Eligibility: BMI ≥30 or ≥27 with weight-related health conditions
- 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 does Mounjaro mean — is it the same as Wegovy?
No. Both are prescription weight loss injections, but Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, whilst Wegovy (semaglutide) is a GLP-1 agonist only. Clinical trials show Mounjaro may produce slightly greater average weight loss (15–21% vs ~15%), but individual results vary. Both are prescription-only and require clinical assessment before starting.
Is Mounjaro available on the NHS in the UK?
Yes, Mounjaro is NICE-approved for NHS use through specialist weight management services. However, availability varies significantly by region and waiting lists can be lengthy. You'll need a GP referral to tier 3 services. Private access is faster — typically available within days through online consultations with UK-licensed prescribers.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs approximately £50–£100 for an online consultation with a prescriber, plus £129–£320 per month for the medication depending on your dose. Costs vary by provider. NHS access is free but involves waiting times. Both routes require a valid UK prescription from a licensed healthcare professional.
What side effects should I expect with Mounjaro in the UK?
Common side effects include nausea, diarrhoea, constipation, and stomach pain — particularly when starting or increasing doses. Most side effects reduce over time as your body adjusts. Seek immediate medical attention for severe stomach pain (possible pancreatitis), serious allergic reactions, or changes in heart rate. Always discuss side effects with your prescriber.
Do I need a GP referral to get Mounjaro privately in the UK?
No — private Mounjaro access does not require an NHS GP referral. You can have an online consultation directly with a UK-licensed prescriber through registered pharmacies. However, it's advisable to inform your GP that you're starting weight loss treatment. NHS access does require a GP referral to specialist services.
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.