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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Meal Ideas When Taking Mounjaro in the UK
When taking Mounjaro (tirzepatide), your appetite naturally decreases and portion sizes reduce significantly. This means you need to rethink your approach to meals — not because you need less nutrition, but because eating becomes fundamentally different. The challenge isn't about "dieting" anymore; it's about choosing foods that work with your Mounjaro side effects (particularly nausea and constipation) whilst ensuring you still get adequate protein, fibre, and nutrients. This guide explores practical meal ideas to support your weight loss journey whilst taking this GLP-1/GIP 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.
What Changes When You Start Mounjaro
Mounjaro works by reducing appetite and making you feel fuller much faster. Most people report that they can only eat a quarter or half of their normal meal portions. The most common side effects are nausea, diarrhoea, and constipation — which directly impact what foods sit well with your body.
Key changes to expect:
- Significantly reduced appetite and faster fullness signals
- Possible nausea, especially in weeks 2–4 of dose increases
- Digestive changes (constipation more common than diarrhoea)
- Reduced tolerance for fatty, greasy, or very sweet foods
- Slower digestion — some people feel uncomfortably full for hours
Your Mounjaro KwikPen dosing increases every 4 weeks (from 2.5 mg through to 15 mg maximum), and side effects often peak during dose escalation weeks. This means your meal tolerance may shift as you progress through your dose titration schedule.
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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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Practical Meal Ideas for Mounjaro Users
Breakfast: Scrambled eggs with toast, Greek yoghurt with berries, porridge with banana, or a smoothie with protein powder. Keep portions small — most people manage one egg and one slice of toast, or a small bowl of yoghurt.
Lunch/Dinner: Grilled chicken breast with roasted vegetables, baked white fish with boiled potatoes, lean mince with rice, or vegetable stir-fry. Prioritise protein and soft foods. Avoid deep-fried items and high-fat cuts.
Snacks: Keep them minimal — a piece of fruit, handful of nuts, cheese string, or a protein bar. Many Mounjaro users skip snacks entirely due to reduced appetite.
Hydration: Drink plenty of water throughout the day to help manage constipation. Aim for at least 8 glasses daily.
- 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.
What foods should I avoid when taking Mounjaro?
Avoid fatty, greasy, fried foods, high-sugar sweets, and very rich meals — these often trigger nausea. Limit alcohol as well. Focus on lean proteins, vegetables, whole grains, and soft foods that digest easily. Spicy foods may also worsen nausea in some people. Listen to your body and adjust accordingly.
How much should I eat when on Mounjaro?
Portion sizes drop dramatically for most people — typically to one quarter or one half of normal portions. Your appetite signals are your guide. Eat slowly, stop when satisfied (not full), and don't force yourself to finish meals. Adequate nutrition matters more than meal size.
Can Mounjaro cause constipation and how does diet help?
Yes — constipation is very common. Increase fibre gradually (vegetables, whole grains, fruit), drink plenty of water, and include foods like prunes or kiwis. Avoid over-the-counter laxatives without GP guidance. Gentle physical activity also helps. If constipation persists, discuss with your prescriber.
Do I need to count calories on Mounjaro?
Calorie counting becomes less critical because Mounjaro significantly reduces appetite and food intake. However, focusing on nutrient-dense foods (protein, vegetables, whole grains) ensures you maintain muscle mass and overall health during weight loss.
Is it safe to eat smaller portions — won't I get malnourished?
When eating smaller portions with Mounjaro, prioritise nutrient-dense foods: lean proteins, vegetables, whole grains, and healthy fats. Most people still consume adequate calories and nutrients at smaller volumes. If concerned about nutritional intake, discuss with your GP or a dietitian registered with the Health and Care Professions Council (HCPC).
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.