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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Botox and Mounjaro — What's the Difference?
Botox and Mounjaro are completely different treatments, and it's important to understand the distinction if you're considering weight management options in the UK. Botox is a cosmetic procedure that temporarily relaxes facial muscles, while Mounjaro (tirzepatide) is a prescription-only weight loss injection that works by regulating appetite hormones. This guide explains how they differ, what Mounjaro actually does for weight management, and how it compares to other licensed options like Wegovy.
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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.
What Mounjaro Actually Is — Not Botox
Mounjaro is a prescription-only weight management injection, not a cosmetic procedure. It contains tirzepatide, a dual GIP and GLP-1 receptor agonist that works inside your body to help regulate appetite and blood sugar control. Unlike Botox — which is injected into facial muscles and is purely cosmetic — Mounjaro is a medical treatment licensed by the MHRA for weight management in UK adults.
Mounjaro is administered as a once-weekly injection using a pre-filled KwikPen device. You inject it into your stomach, thigh, or upper arm. The medication works by activating two natural hormone pathways in your body, which may help reduce food cravings, increase satiety (feeling fuller), and support sustainable weight loss alongside dietary changes and physical activity.
Key differences from Botox: Mounjaro requires a clinical assessment from a licensed prescriber, is taken regularly (not a one-off procedure), works internally on appetite regulation, and must be prescribed based on your individual health profile and eligibility.
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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 Wegovy — Trial Data and Mechanisms
Both Mounjaro and Wegovy are prescription weight loss injections available in the UK, but they work differently. Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), while Wegovy (semaglutide) activates one (GLP-1 only). In the SURMOUNT clinical trial, Mounjaro resulted in average weight loss of approximately 15–21% of body weight, depending on dose. Wegovy's STEP trials showed average weight loss of around 15% at the maximum dose.
Individual results vary significantly. Your prescriber will assess which medication is suitable based on your BMI, health conditions, and medical history. Both require a clinical assessment before prescription. Neither is cosmetic — both are pharmaceutical treatments for medical weight management. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses, and our BMI calculator to check whether you may be eligible for prescription support.
- 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 the same as Botox?
No. Botox is a cosmetic procedure injected into facial muscles. Mounjaro is a prescription weight loss injection that works internally on appetite regulation. They are completely different treatments with different purposes, mechanisms, and clinical contexts.
How does Mounjaro help with weight loss?
Mounjaro contains tirzepatide, which activates GIP and GLP-1 hormone pathways. This may reduce appetite, increase feelings of fullness, and slow gastric emptying. It works alongside a reduced-calorie diet and increased physical activity — it is not a standalone solution.
Is Mounjaro available on the NHS in the UK?
Mounjaro has been approved by NICE for use within NHS tier 3 specialist weight management services. However, availability varies significantly by region, and waiting lists can be lengthy. Private prescription through online clinical assessment is also an option.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP + GLP-1 agonist; Wegovy (semaglutide) is a GLP-1 agonist only. Mounjaro's starting dose is 2.5mg weekly (maximum 15mg); Wegovy starts at 0.25mg (maximum 2.4mg). Clinical trials show similar average weight loss, but individual responses vary.
Do I need a prescription to get Mounjaro?
Yes. Mounjaro is prescription-only in the UK. You need a clinical assessment from a licensed prescriber who will evaluate your BMI, health conditions, and medical history. Access is through NHS specialist services or private online prescribing with GPhC-registered pharmacies.
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.