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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What To Eat When On Mounjaro UK
When starting a weight loss injection like Mounjaro (tirzepatide), food choices matter just as much as the medication itself. Mounjaro works by reducing appetite and helping you feel fuller faster, but what you eat during treatment affects both how well the injection works and how you feel day-to-day. This guide covers practical dietary advice for people taking Mounjaro in the UK, including foods to prioritise, what to avoid, and how to manage common side effects like nausea. Always follow your prescriber's guidance on diet alongside your Mounjaro UK prescription.
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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.
Foods To Prioritise When Taking Mounjaro
Since Mounjaro reduces appetite and slows gastric emptying (how quickly food leaves your stomach), prioritise foods that are nutrient-dense, protein-rich, and easy to digest. These support healthy weight loss without leaving you feeling deprived.
- Lean proteins: Chicken, turkey, fish, eggs, Greek yoghurt, cottage cheese. Protein helps maintain muscle mass during weight loss and increases satiety.
- Non-starchy vegetables: Broccoli, spinach, courgettes, peppers, asparagus, green beans. High in fibre and nutrients, low in calories.
- Whole grains (in moderation): Brown rice, oats, quinoa, wholemeal bread. Better than refined carbs for sustained energy.
- Healthy fats: Olive oil, avocado, nuts, seeds. Support hormone function and nutrient absorption.
- Low-sugar fruits: Berries, apples, oranges. Provide vitamins without excess sugar spikes.
Start meals with protein and vegetables — this approach aligns with how Mounjaro helps regulate appetite and blood sugar.
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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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Foods To Avoid And Managing Side Effects
Certain foods may worsen common Mounjaro side effects like nausea, vomiting, and constipation. Avoid high-fat, greasy, and very sugary foods — these are harder to digest and may trigger nausea. Skip spicy food initially if your stomach feels sensitive.
- Fried and fatty foods: Chips, pastries, creamy sauces. These slow digestion and increase nausea risk.
- High-sugar foods: Biscuits, sweets, sugary drinks. May cause blood sugar fluctuations and energy crashes.
- Very large meals: Mounjaro makes you feel full quickly — eating large portions can cause discomfort and nausea.
- Alcohol: Can trigger nausea and dehydration. Drink in moderation if at all.
Stay hydrated throughout the day — aim for at least 2 litres of water. If constipation occurs, gradually increase fibre intake and consult your GP.
- 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.
Can I eat normally while on Mounjaro?
Not quite the same way. Mounjaro reduces appetite significantly, so you'll likely feel full on smaller portions. You'll eat less naturally, but what you eat should still be nutritious. Focus on whole foods, protein, and vegetables rather than processed snacks. Your prescriber can advise on calorie targets.
How much should I eat when taking Mounjaro?
Portion sizes decrease naturally as Mounjaro works. Listen to your hunger cues — the injection helps regulate these. Most people find they eat around 30–50% less without feeling deprived. Work with your prescriber or a registered dietitian to set appropriate calorie targets for your weight loss goals.
What should I do if I feel nauseous on Mounjaro?
Nausea is common, especially in the first weeks. Try eating smaller, more frequent meals; avoid fatty and greasy foods; stay hydrated; eat slowly; and choose bland, easy-to-digest options like toast, crackers, plain rice, or chicken. If severe nausea persists, contact your GP — your dose may need adjusting.
Should I follow a specific diet while on Mounjaro?
No single diet is required, but a balanced, whole-food approach works best. Focus on protein, vegetables, whole grains, and healthy fats. Avoid processed foods, excess sugar, and large portions. Many people find a Mediterranean-style diet effective. Your GP or a registered dietitian can provide personalised dietary guidance.
Do I need to track calories while on Mounjaro?
Not necessarily. Since Mounjaro naturally reduces appetite, many people find calorie tracking unnecessary. However, tracking can help if weight loss plateaus or you're unsure whether you're eating enough. Use our free progress tracker alongside MyWeightCheck's GLP-1 weight loss calculator to monitor your journey alongside dietary changes.
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.