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 Using Mounjaro
When you start using Mounjaro (tirzepatide), your appetite and relationship with food changes significantly. This guide explains what to eat during treatment, how to manage nausea and side effects through nutrition, and which foods work best alongside your medication. Mounjaro is a prescription-only GLP-1 and GIP receptor agonist that helps reduce hunger — but choosing the right foods supports better results and minimises digestive discomfort. Individual experiences vary, so work with your GP or a healthcare professional to tailor your diet to your needs.
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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.
Nutrition Choices During Mounjaro Treatment
When using Mounjaro, smaller portions of nutrient-dense foods work better than large meals. Many people find they naturally eat less — this is the medication working as intended. Focus on:
- Lean proteins: chicken, fish, eggs, Greek yoghurt, lentils — help maintain muscle and keep you full longer
- Non-starchy vegetables: broccoli, spinach, peppers, courgettes — low calorie, high fibre, gentle on digestion
- Whole grains: oats, brown rice, quinoa — in smaller quantities than before
- Healthy fats: avocado, olive oil, nuts (in small amounts) — important for nutrient absorption
Avoid or limit high-fat, greasy, and processed foods — these trigger nausea and stomach upset more readily on Mounjaro. Salty or heavily spiced foods may also cause discomfort early in your treatment. Drink plenty of water throughout the day; dehydration worsens nausea.
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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.
Free Weight Loss Tools & Guides
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Managing Side Effects Through Food Choices
Nausea, constipation, and indigestion are common when starting Mounjaro or increasing your dose. Eating smaller, more frequent meals helps — aim for 4–5 small meals rather than 2–3 large ones. Ginger tea, plain crackers, and broth-based soups often ease nausea. If you experience constipation, increase fibre gradually and ensure adequate hydration. Avoid fizzy drinks, which can cause bloating.
Keep a simple food diary for the first few weeks — this helps you identify which foods feel comfortable and which trigger side effects. Use our free GLP-1 weight loss calculator to track your estimated progress as your diet adapts; this helps you see the positive results alongside your nutrition changes. Your GP can refer you to a dietitian if you need personalised meal planning support.
- 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 once the Mounjaro dose stabilises?
Many people continue to eat smaller portions even at stable doses because the appetite-suppressing effect of tirzepatide persists. However, you may tolerate a slightly wider variety of foods. Focus on balanced, nutrient-dense choices rather than returning to pre-treatment portion sizes — this supports ongoing weight loss and health benefits.
Is it safe to skip meals when using Mounjaro because I'm not hungry?
It's important to eat regular, balanced meals even if you're not hungry. Skipping meals can lead to nutrient deficiencies and low energy. Mounjaro reduces appetite, but your body still needs protein, vitamins, and minerals. Eat smaller, regular meals rather than no meals.
What should I do if I feel sick after eating on Mounjaro?
Nausea usually improves as your body adjusts, but it's unpleasant. Try eating slowly, choosing bland foods (plain chicken, rice, toast), and avoiding high-fat or spicy dishes. Ginger tea and frequent sips of water help. If nausea persists beyond the first few weeks or worsens, contact your GP — it may indicate a dose adjustment is needed.
Are there foods I should completely avoid while on Mounjaro?
There are no completely forbidden foods, but some are better tolerated than others. High-fat, fried, and heavily processed foods are more likely to cause nausea and stomach upset. Limit alcohol, which can trigger side effects. Your GP or a dietitian can advise on your individual tolerances.
How does eating on Mounjaro compare to Wegovy?
Both Mounjaro and Wegovy (semaglutide) reduce appetite similarly, so nutrition principles are comparable. However, some people find they tolerate different foods on each medication. Individual responses vary — what works well for one person may not for another. A GP can help you personalise your approach.
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.