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 While Taking Mounjaro
While taking Mounjaro (tirzepatide), certain foods may worsen side effects like nausea, diarrhoea, and stomach pain. Understanding which foods to limit or avoid can help you manage your treatment more comfortably and support steady weight loss. This guide covers practical dietary advice for UK adults using this prescription-only injection, alongside how to maintain a balanced diet during your tirzepatide journey.
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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 and Drinks to Avoid or Limit
When taking Mounjaro, your appetite and food tolerance naturally change. Some foods are more likely to trigger side effects or discomfort:
- Fatty or greasy foods — can worsen nausea, diarrhoea, and stomach pain. Limit fried foods, full-fat cheese, and greasy takeaways
- High-sugar foods and drinks — may cause nausea and blood sugar spikes. Avoid sugary sweets, fizzy drinks, and desserts
- Spicy foods — can irritate the stomach and trigger indigestion or reflux, especially early in treatment
- Alcohol — may worsen nausea and diarrhoea; also increases dehydration risk
- Large, heavy meals — harder to digest and more likely to cause stomach discomfort. Smaller, frequent meals work better
- Caffeine in excess — can worsen nausea and stomach sensitivity, though moderate amounts are usually fine
Individual tolerance varies — track how different foods make you feel and adjust accordingly. Your GP can offer personalised dietary guidance if you have concerns.
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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.
Foods That Work Well on Mounjaro
Focus on easily digestible, nutrient-dense foods that support steady weight loss and minimise side effects:
- Lean proteins — chicken, fish, turkey, eggs, tofu
- Colourful vegetables — broccoli, spinach, peppers, carrots
- Whole grains — oats, brown rice, quinoa in small portions
- Low-fat yoghurt and cottage cheese
- Fruits — apples, berries, bananas, oranges
- Healthy fats in moderation — olive oil, nuts, avocado
Stay hydrated with water and herbal tea. Eating slowly and chewing well helps your body digest comfortably. Use our GLP-1 weight loss calculator to track your progress and monitor how dietary changes support your treatment goals alongside tirzepatide.
- 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.
Why do I feel nauseous on Mounjaro when I eat certain foods?
Mounjaro slows how quickly food leaves your stomach and reduces appetite signals. Fatty, greasy, or heavy foods are harder to digest and more likely to trigger nausea. Switching to lighter, protein-rich meals usually helps. If nausea persists beyond the first few weeks, speak to your GP.
Can I eat normal food while taking Mounjaro?
Yes, you can eat normal food — but portion sizes naturally shrink because Mounjaro makes you feel fuller faster. Many people find they're satisfied with smaller amounts. The key is choosing nutrient-dense foods, staying hydrated, and eating slowly. Your appetite will guide you.
Should I avoid alcohol completely on Mounjaro?
You don't have to avoid alcohol completely, but it's best to limit it. Alcohol can worsen nausea and diarrhoea, and tirzepatide increases dehydration risk. If you do drink, do so in moderation and always with food. Discuss your alcohol habits with your GP if you're concerned.
What if I'm still hungry on Mounjaro but feel sick after eating?
This is common early in treatment — nausea typically reduces over time. Eat smaller, more frequent meals throughout the day. Focus on protein and fibre, which keep you fuller longer with less food. If nausea persists beyond a few weeks, contact your prescriber about dose adjustment.
Do I need to follow a specific diet while taking Mounjaro?
There's no single "Mounjaro diet" — but weight loss is most effective when you combine tirzepatide with a reduced-calorie diet and increased physical activity. Focus on whole foods, adequate protein, plenty of vegetables, and hydration. Your GP or a dietitian can offer personalised guidance based on your health.
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.