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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Foods to Avoid on Mounjaro — A UK Health Guide
If you're taking Mounjaro (tirzepatide) as a prescription weight loss injection, certain foods may trigger or worsen common side effects like nausea, stomach pain, and diarrhoea. This guide explains which foods to avoid or limit while on Mounjaro, aligned with NHS and clinical trial evidence. Individual responses vary — your GP can provide personalised dietary advice. Remember that Mounjaro works best alongside a reduced-calorie diet and increased physical activity, so managing what you eat is an important part of your weight loss journey.
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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.
Which Foods to Avoid on Mounjaro
When taking Mounjaro, certain foods are more likely to cause digestive discomfort. Avoid or limit high-fat foods (fried foods, cream-based sauces, fatty meats, full-fat dairy) as these slow stomach emptying and can trigger nausea and diarrhoea. Very sugary foods (sweets, fizzy drinks, cakes, desserts) may cause stomach upset and don't align with your weight loss goals. Spicy foods can irritate the stomach in some people — if you tolerate them normally, try reintroducing them slowly. Large meals are harder to digest on Mounjaro; eat smaller, more frequent meals instead. Alcohol can amplify side effects and dehydration risk, particularly in the early weeks of your dose titration. Caffeine on an empty stomach may worsen nausea — have it with food. Foods that are fresh, lean, and nutrient-dense — like chicken, fish, vegetables, whole grains, and legumes — are typically better tolerated and support your weight loss.
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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
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Managing Side Effects Through Diet
Many people experience nausea, constipation, or diarrhoea during their Mounjaro dose titration (the gradual increase from 2.5mg to your maintenance dose). Dietary choices can significantly reduce symptom severity. Eat slowly and chew thoroughly — this aids digestion and prevents stomach distension. Stay hydrated with water, herbal tea, and broth. If you experience constipation, increase fibre gradually and drink more water; if diarrhoea occurs, eat bland, easy-to-digest foods like toast, rice, and boiled potatoes. Keep a food diary to identify which specific foods trigger your symptoms, as individual tolerance varies. Your GP or a registered dietitian can offer personalised guidance. Our GLP-1 weight loss calculator can help you understand expected weight loss outcomes alongside these dietary adjustments.
- 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 bread and carbohydrates on Mounjaro?
Yes. Mounjaro doesn't require avoiding any food group entirely. Whole grain breads, oats, and complex carbohydrates are fine — they're actually better than refined carbs as they keep you fuller longer. Portion control matters more than food type. Your reduced appetite from Mounjaro naturally supports eating less.
What should I eat if I'm feeling nauseous on Mounjaro?
Stick to bland, easy-to-digest foods: crackers, toast, rice, boiled vegetables, plain chicken, and soup. Ginger tea or ginger biscuits may help. Eat smaller meals more frequently. Avoid anything greasy, spicy, or sweet. Most nausea improves after the first few weeks as your body adjusts to your dose.
Is alcohol safe while taking Mounjaro?
Alcohol can worsen nausea, dehydration, and stomach upset — especially in the first weeks. If you do drink, do so moderately with food and alongside plenty of water. Your GP can advise based on your health. Alcohol is also calorie-dense, which may slow weight loss progress.
Can I use our weight converter to track if my food choices are supporting weight loss?
While the weight converter helps you understand your weight in different units (kg, stone, lbs), tracking your overall calorie intake and physical activity is what drives weight loss on Mounjaro. Use our progress tracker to log your weight weekly and see how your dietary choices impact your results over time.
Should I follow a specific diet like low-carb or keto on Mounjaro?
No specific diet is required. A balanced, reduced-calorie diet works best — focus on lean proteins, vegetables, whole grains, and healthy fats in smaller portions. Mounjaro reduces your appetite naturally, so restrictive diets are often unnecessary and harder to sustain. Your GP or a dietitian can recommend an approach suited to your lifestyle.
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.