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 Compared to Other Weight Loss Treatments in the UK
If you're considering weight loss treatment in the UK, you've likely heard of Mounjaro alongside other options like Wegovy and lifestyle programmes. This guide compares Mounjaro (tirzepatide) with other available approaches, helping you understand how they differ and what might suit your situation. All prescription weight loss medications require a clinical assessment from a UK-licensed prescriber before use. Use our free GLP-1 weight loss calculator to explore potential outcomes with different approaches, and check your BMI using our calculator to understand your starting point.
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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.
How Mounjaro Differs from Other Prescription Weight Loss Options
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — a prescription-only weight loss injection licensed in the UK. Clinical trials showed participants lost an average of 15–21% of their body weight over 72 weeks, though individual results vary significantly. Mounjaro is given as a once-weekly KwikPen injection, with doses ranging from 2.5 mg to 15 mg.
Wegovy (semaglutide) is a GLP-1 receptor agonist only — it activates one hormone pathway rather than Mounjaro's dual mechanism. STEP trial data showed average weight loss of around 15% body weight. Wegovy is also once-weekly, with a maximum dose of 2.4 mg.
Key differences include: Mounjaro typically produces slightly higher average weight loss in trials, has a higher maximum dose, and uses a different mechanism. Both are prescription-only and require clinical assessment. Both work best alongside reduced-calorie diet and increased physical activity. Cost and availability may differ between NHS and private access routes.
Clinically BackedWeight Loss
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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.
Mounjaro vs Lifestyle Changes and NHS-Supported Options
The NHS recommends a stepped approach to weight management. Tier 1 involves self-help tools, digital apps, and community programmes — many are free. Tier 2 includes GP-led behaviour change support and group weight loss programmes. Tier 3 is specialist weight management services, where prescription medications like Mounjaro may be considered. Tier 4 covers bariatric surgery for severe obesity.
Prescription medications like Mounjaro are typically used when lifestyle changes alone haven't achieved sufficient weight loss, or when weight-related health conditions exist. They work alongside diet and activity changes, not instead of them. The NHS KwikPen prescription pathway for tirzepatide access varies by region — many areas have long waiting lists. Private prescribing offers faster access but at a cost.
- 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 Mounjaro better than Wegovy for weight loss in the UK?
Both medications help with weight loss, but results vary individually. Mounjaro showed slightly higher average weight loss in clinical trials (15–21% vs 15% for Wegovy), but this doesn't mean it will work better for you personally. Your prescriber will assess which is more suitable based on your health profile, medical history, and any other medications you take.
Can I get Mounjaro on the NHS in the UK?
Mounjaro is available through NHS specialist tier 3 weight management services following NICE approval. However, access varies significantly by region and waiting lists can be very long in many areas. Private prescribing through a licensed UK prescriber offers faster access without NHS referral, though at a cost typically ranging from £129–£320+ per month depending on dose.
What's the difference between Mounjaro and Ozempic?
Both contain the same active ingredient, but Mounjaro is specifically licensed for weight management while Ozempic is licensed for type 2 diabetes at lower doses. Using Ozempic for weight loss would be off-label (unlicensed use). Mounjaro is the correct prescription option if weight loss is your primary goal in the UK.
How quickly does Mounjaro work compared to diet and exercise alone?
Mounjaro may help suppress appetite and reduce food cravings within weeks, though weight loss becomes noticeable over several months. Diet and exercise alone typically result in slower weight loss (0.5–1 kg per week). Mounjaro is most effective when combined with dietary changes and activity — it's not a replacement for lifestyle changes.
Do I need a prescription to buy Mounjaro in the UK?
Yes, Mounjaro is prescription-only. You cannot buy it without a valid UK prescription from a licensed prescriber. You can obtain a prescription through NHS specialist services (referral from your GP) or through a private online consultation with a UK-licensed prescriber who will assess your eligibility before issuing a 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.