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
Free tracker included with every download this week
What Food Should You Avoid While Taking Mounjaro?
When taking Mounjaro (tirzepatide), certain foods may worsen common side effects like nausea, diarrhoea, and indigestion. While Mounjaro doesn't require strict food restrictions like some medications, being mindful of your diet can make your treatment more comfortable and effective. This guide explains which foods to limit or avoid, why they may be problematic, and how to build a sustainable eating pattern alongside your Mounjaro prescription. Your GP or prescriber can give personalised dietary advice based on your individual response to treatment.
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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 That May Worsen Mounjaro Side Effects
The most common side effects of Mounjaro are gastrointestinal — nausea, diarrhoea, constipation, and stomach discomfort. Certain foods can intensify these effects. Fatty and greasy foods often trigger nausea and indigestion, especially early in treatment. High-fibre foods eaten in large quantities may worsen diarrhoea, particularly during dose escalation. Spicy foods can irritate the stomach and increase acid reflux. Caffeine and alcohol may exacerbate nausea and digestive discomfort. Sugary foods and drinks are less likely to cause side effects but offer little nutritional value and can trigger cravings — counterproductive to weight loss goals. Large, heavy meals are harder to tolerate than smaller, frequent meals. The good news is that Mounjaro's appetite-suppressing effect naturally reduces the appeal of many of these foods.
Clinically BackedWeight 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.
Building a Mounjaro-Friendly Diet
Focus on lean proteins, vegetables, and whole grains in smaller portions. Protein is especially important — it supports muscle preservation during weight loss and helps maintain satiety. Cooked vegetables are gentler than raw ones; boiling or steaming aids digestion. Lower-fat dairy, eggs, chicken, and fish are well-tolerated. Drink plenty of water to manage constipation — the NHS recommends 6–8 glasses daily. Ginger tea, peppermint, and plain broth can help settle nausea. Keep a food diary to track which foods trigger your side effects — individual tolerance varies significantly. Your prescriber or a registered dietitian can help refine your approach. Use our free weight loss calculator to monitor your progress as you adjust your diet with Mounjaro treatment.
- 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 on Mounjaro?
You can eat normal foods, but Mounjaro's appetite-suppressing effect means you'll likely feel full faster and eat less overall. Avoid foods that trigger your specific side effects. Most people naturally reduce portion sizes without conscious restriction. Your prescriber can advise on any personal dietary modifications.
Should I avoid all fatty foods on Mounjaro?
No strict ban exists, but high-fat foods often trigger nausea and indigestion — especially early in treatment. Small amounts of healthy fats (olive oil, nuts, avocado) are fine. Avoid deep-fried, greasy takeaway foods. You may find your tolerance improves as your body adjusts to the medication.
Is it safe to eat spicy food on Mounjaro?
Spicy foods can worsen acid reflux and stomach discomfort in some people taking Mounjaro. If you enjoy spiced food, try milder versions or reduce portion sizes initially. Monitor your symptoms and adjust based on your individual tolerance — some people tolerate spice well.
Can Mounjaro cause food allergies or intolerances?
Mounjaro itself doesn't cause new food allergies, but gastrointestinal side effects may make certain foods feel intolerable temporarily. This usually improves as your body adjusts. Pre-existing allergies and intolerances remain unchanged. Always inform your prescriber of known food allergies before starting treatment.
What if I'm struggling with food choices on Mounjaro?
Request a referral to a registered dietitian or nutritionist through your GP — they can provide personalised dietary guidance while taking Mounjaro (tirzepatide). Many NHS weight management services include dietitian support. Track your tolerance using our free progress tracker to identify patterns and discuss findings with your healthcare team.
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.