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
Is Mounjaro Just An Appetite Suppressant?
No — Mounjaro (tirzepatide) is not just an appetite suppressant. While it does help reduce hunger, it works through a dual-action mechanism that sets it apart from simple appetite suppressants. Mounjaro activates two separate hormone pathways (GIP and GLP-1), which means it helps regulate appetite, fat metabolism, and blood sugar control simultaneously. This multi-targeted approach is what distinguishes it from single-mechanism medications like Wegovy, which activates only the GLP-1 pathway. Understanding how Mounjaro actually works helps explain why results vary between individuals and why a prescriber assessment is essential before use.
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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 — Dual Action vs Single-Mechanism Alternatives
Mounjaro's dual GIP and GLP-1 action means it works on two separate appetite and metabolism control systems. GIP (glucose-dependent insulinotropic polypeptide) regulates fat usage and energy expenditure, whilst GLP-1 controls hunger signals and fullness cues. Together, they help reduce food cravings, support feeling fuller after smaller portions, and slow how quickly food moves through your stomach.
By contrast, Wegovy (semaglutide) activates only the GLP-1 pathway, making it a single-mechanism GLP-1 agonist. In clinical trials, this difference showed measurable outcomes: SURMOUNT-1 (Mounjaro) demonstrated average weight loss of approximately 20.9% at the maximum 15 mg dose, whilst STEP-1 (Wegovy) showed approximately 14.9% at the 2.4 mg dose — though individual results vary significantly and both require a reduced-calorie diet and increased physical activity.
Neither medication is simply an appetite suppressant; both are prescription-only receptor agonists that require a clinical assessment and ongoing prescriber monitoring.
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.
Which Is Right For You — Eligibility and Individual Suitability
Both Mounjaro and Wegovy are available to UK adults with a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea. Access depends on whether you're seeking NHS specialist services (through tier 3 weight management teams) or private prescription following an online clinical assessment.
Your prescriber will assess which medication suits you based on your health history, existing medications, and individual circumstances — it's not a choice you make alone. Some people respond better to dual-action tirzepatide; others achieve excellent results with GLP-1-only semaglutide. Use our free GLP-1 weight loss calculator to estimate potential weight loss at different doses, and consult your GP or a licensed prescriber for personalised advice on suitability.
- 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 an appetite suppressant?
Mounjaro reduces appetite, but it's more than just a suppressant. It's a dual GIP and GLP-1 receptor agonist that regulates appetite, fat metabolism, blood sugar, and how quickly food leaves your stomach. This multi-targeted action is why results differ from traditional appetite suppressants.
What's the difference between Mounjaro and Wegovy mechanisms?
Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), whilst Wegovy (semaglutide) activates only GLP-1. This dual action in Mounjaro may contribute to higher average weight loss in clinical trials — roughly 20.9% versus 14.9% — though individual outcomes vary significantly.
Can I get Mounjaro on the NHS in the UK?
Mounjaro is approved by NICE for NHS specialist weight management services (tier 3 teams). Access varies by region and waiting times can be long. Private prescription is available through online clinical assessment with a UK-licensed prescriber.
How do I know if Mounjaro or Wegovy is right for me?
A prescriber will assess your eligibility based on BMI, health conditions, current medications, and medical history. Both require a clinical assessment. Try our free GLP-1 weight loss calculator to see projected outcomes at different doses, then discuss with your GP.
Is Mounjaro a kwikpen like Wegovy?
Mounjaro comes as a pre-filled KwikPen auto-injection device (once weekly), whilst Wegovy is a pre-filled auto-injection pen (also once weekly). Both are prescription-only and require proper storage and injection technique training from your prescriber.
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.