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
Mounjaro and Struggling to Eat — What You Need to Know
Struggling to eat while taking Mounjaro is one of the most common side effects reported by users in the UK. Mounjaro (tirzepatide) works by activating two natural hormone pathways — GIP and GLP-1 — which help regulate appetite and create feelings of fullness. This appetite suppression is intentional but can sometimes feel overwhelming, especially during the early weeks. Understanding why this happens and how to manage it safely is important for your health and wellbeing while using this prescription medication.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Affects Your Appetite
Mounjaro's dual mechanism works on appetite control in multiple ways. The GLP-1 pathway signals to your brain that you are full, while the GIP pathway helps regulate how your body uses glucose and fat. Together, these effects slow gastric emptying — the speed at which food leaves your stomach — which intensifies feelings of fullness even after small meals.
In clinical trials, many participants experienced significant appetite reduction, particularly in the first 4–8 weeks after starting or increasing their tirzepatide dose. This reduced appetite is the primary reason Mounjaro helps support weight management. However, the effect is often stronger than expected, and some people struggle to eat enough calories to sustain energy and muscle mass. This is why dose titration — gradually increasing from 2.5 mg over several weeks — is standard NHS practice. Starting low allows your body to adjust before reaching higher doses where appetite suppression is more pronounced.
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.
Managing Reduced Appetite Safely
If you're struggling to eat on Mounjaro, prioritise nutrient-dense foods over quantity. Choose protein-rich options like eggs, yoghurt, fish, and pulses — even small portions support muscle maintenance. Broths, smoothies, and soups may feel easier to consume than solid meals. Stay hydrated with water throughout the day, as thirst can be mistaken for hunger.
It's essential not to force yourself to eat below your body's needs. Sustained calorie restriction below 1200 kcal/day without medical supervision can lead to nutrient deficiencies, muscle loss, and fatigue. If you're consistently unable to eat adequate food, contact your GP or the prescriber who issued your Mounjaro UK prescription. They may adjust your dose, provide additional support, or discuss whether continuing treatment is appropriate for you.
- 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 struggling to eat on Mounjaro normal?
Yes, appetite suppression is a common and expected side effect, especially in weeks 1–8 and after dose increases. Most people adjust within 2–4 weeks. However, if you feel unable to eat enough to maintain energy and health, speak to your GP. This is not something you should simply tolerate.
When should I contact my GP about appetite loss?
Contact your GP if you cannot eat sufficient food to meet basic calorie needs, experience persistent nausea alongside loss of appetite, feel dizzy or extremely fatigued, or notice significant muscle weakness. These may indicate your dose needs adjustment or that Mounjaro isn't the right choice for you.
Should I force myself to eat while on Mounjaro?
No. Forcing food can worsen nausea. Instead, eat small, frequent, nutrient-dense meals when you feel able. Focus on protein and healthy fats. If appetite suppression becomes severe, your prescriber may pause dose increases or discuss alternatives.
How does Mounjaro's appetite effect compare to Wegovy?
Both medications suppress appetite through GLP-1 pathways. Mounjaro also includes a GIP agonist component, which may intensify appetite suppression for some users. Individual responses vary significantly, and some people find one medication easier to manage than the other.
Can I use the GLP-1 weight loss calculator to plan meals?
Our free GLP-1 weight loss calculator projects potential weight loss at different doses, which can help you understand what to expect. However, use our BMI calculator and progress tracker alongside it to monitor whether your current food intake is supporting your health alongside weight loss goals.
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.