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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Not Hungry On Mounjaro — How It Compares To Wegovy
Reduced appetite is one of the most commonly reported effects of Mounjaro, and many people wonder how this compares to other weight loss injections like Wegovy. Both are prescription-only medications that work by activating appetite-regulating pathways in the brain, but they use different mechanisms. This guide explains why you may not feel hungry on Mounjaro, how Wegovy's appetite suppression differs, and what clinical trial data tells us about appetite changes with each medication.
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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 And Wegovy Work Differently On Appetite
Mounjaro (tirzepatide) activates two hormone pathways: GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1). This dual-action mechanism may help regulate appetite through multiple routes in the brain and gut, which is why many users report strong appetite suppression. Wegovy (semaglutide) activates GLP-1 receptors only, using a single pathway to signal satiety and reduce hunger signals.
In clinical trials, both medications reduced appetite, but Mounjaro users in the SURMOUNT-1 study reported average weight loss of approximately 20.9% at the maximum 15 mg dose, whilst Wegovy users in the STEP-1 trial achieved approximately 14.9% average weight loss at the 2.4 mg maximum dose. These differences may partly reflect the dual-mechanism advantage of tirzepatide, though individual responses vary significantly. Both require a prescription following a clinical assessment, and both are taken as once-weekly injections when prescribed in the UK.
- Mounjaro: dual GIP + GLP-1 activation — two appetite pathways
- Wegovy: GLP-1 activation only — single appetite pathway
- Both slow gastric emptying and increase feelings of fullness
- Both reported to reduce cravings and food preoccupation
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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.
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Which Medication Is Right For You — An Individual Choice
The choice between Mounjaro and Wegovy is not about which is "better" — it's about which is more suitable for your individual health profile, medical history, and prescriber's clinical judgment. A UK-licensed prescriber will assess factors including your BMI, weight-related health conditions, current medications, and any previous weight loss treatment responses to determine the most appropriate option for you. Some patients are prescribed Mounjaro; others are prescribed Wegovy. Some may switch between them based on individual response or tolerance. Both are prescription-only and available through NHS specialist weight management services or private online prescribing following clinical assessment.
Our free GLP-1 weight loss calculator above can help you explore projected weight loss at different doses of either medication, though results always vary. Use your BMI calculator to check your current status and discuss your individual suitability with a prescriber.
- 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.
Why am I not hungry on Mounjaro when I was before?
Mounjaro activates GIP and GLP-1 receptors in your brain and gut, which signal fullness, reduce appetite hormones, and slow how quickly food leaves your stomach. This combination typically results in reduced hunger, fewer cravings, and eating smaller portions naturally. The effect usually builds gradually as your dose increases over 4–5 months.
Is appetite suppression stronger on Mounjaro than Wegovy?
Clinical trial data suggests Mounjaro's dual-mechanism approach may produce greater average weight loss (approximately 20.9% vs 14.9%), which could reflect stronger appetite suppression. However, individual responses vary considerably — some people feel equally suppressed on either medication, whilst others respond better to one or the other. Your prescriber will assess which suits you best.
Does appetite suppression continue or does your body adapt?
Most users report sustained appetite reduction whilst taking Mounjaro, though some mild adaptation can occur over time. Staying hydrated, eating nutrient-dense foods, and maintaining physical activity helps manage the appetite-suppressing effect. If adaptation occurs, your dose may be adjusted by your prescriber.
What if I'm not hungry enough on Mounjaro — is that a problem?
Some patients experience very low appetite, which can lead to under-eating and insufficient nutrient intake. If you struggle to eat enough, speak to your prescriber or a dietitian. They may adjust your dose, recommend smaller frequent meals, or ensure you're meeting protein and micronutrient needs. This is an important conversation to have.
Can I take Mounjaro or Wegovy if I'm already taking appetite-suppressant medication?
Both GLP-1 and dual GIP/GLP-1 medications can interact with other appetite-affecting drugs. Always inform your prescriber of all current medications before starting either Mounjaro or Wegovy. A clinical assessment will determine whether it's safe to combine treatments or adjust other medications.
Ready to take control of your weight loss journey?
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