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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Mounjaro Foods to Avoid — A Practical UK Guide
If you're taking Mounjaro (tirzepatide), certain foods may trigger nausea, stomach discomfort, or other side effects — especially when you first start or increase your dose. This guide explains which foods are best avoided on Mounjaro, how Wegovy compares in terms of dietary triggers, and practical strategies to manage your diet while on treatment. Use our GLP-1 weight loss calculator above to track your progress alongside dietary changes.
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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.
Foods to Avoid on Mounjaro vs Wegovy — Trial Data Context
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) activate GLP-1 pathways but work slightly differently. Mounjaro is a dual GIP and GLP-1 receptor agonist, while Wegovy is a GLP-1-only agonist. In the SURMOUNT trials, Mounjaro participants reported similar gastrointestinal side effects to Wegovy users — predominantly nausea, constipation, and diarrhoea. The key difference is that Mounjaro's dual mechanism may cause slightly slower gastric emptying initially, meaning food tolerance can take 4–6 weeks to stabilise. Wegovy (from STEP trials) shows comparable symptom patterns. Individual food triggers vary widely, so what causes nausea in one person may be tolerated by another.
- High-fat foods: Fried foods, fatty cuts of meat, cream-based sauces — may trigger nausea and stomach pain
- High-sugar foods: Sugary drinks, sweets, desserts — can worsen nausea and cause abdominal discomfort
- Spicy foods: Chilli, curry, hot sauces — may irritate the stomach lining
- Large meals: Eating too much at once worsens nausea — smaller, frequent meals work better
- Carbonated drinks: Fizzy beverages can cause bloating and stomach pain
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.
Practical Dietary Strategies — Individual Suitability Matters
The best approach is gentle trial and error. Start with bland, easily digestible foods: plain rice, boiled vegetables, lean proteins, wholemeal bread, and herbal tea. Keep a food diary to identify your personal triggers — nausea timing and severity are individual. Stay hydrated with water or electrolyte drinks. Your prescriber or a registered dietitian can provide personalised advice based on your specific response. Both Mounjaro and Wegovy require a clinical assessment before prescription, so discuss dietary concerns with your healthcare provider when being assessed for eligibility. Track your weight loss progress using our free progress tracker to see how dietary adjustments support your treatment goals alongside medication.
- 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?
Most people can eat normal foods on Mounjaro, but portion sizes naturally reduce due to increased fullness. High-fat, sugary, and spicy foods commonly trigger nausea — especially in the first 4–6 weeks. Many people find they prefer lighter meals. Your appetite naturally suppresses, so forcing large meals can cause discomfort.
Are the food restrictions the same on Wegovy?
Largely yes — both Mounjaro and Wegovy trigger similar gastrointestinal side effects and food intolerances because they both activate GLP-1 pathways. High-fat and high-sugar foods are problematic on both. Individual triggers vary, so what causes issues for one person may be fine for another. Prescriber guidance applies to both.
How long before food tolerance improves on Mounjaro?
Typically 4–6 weeks as your body adjusts to each dose. Side effects often peak in the first 2 weeks, then gradually improve. Once you reach your maintenance dose, food tolerance usually stabilises further. If nausea persists beyond 8 weeks, contact your prescriber.
Should I follow a specific diet while on Mounjaro?
No single prescribed diet works for everyone. Focus on whole foods, lean proteins, vegetables, and adequate hydration. Avoid your personal triggers — use our GLP-1 weight loss calculator to monitor progress. A registered dietitian can provide personalised meal planning if needed.
What if I can't tolerate food on Mounjaro — is it normal?
Difficulty eating is common initially but should improve over weeks. If you experience severe vomiting, inability to keep food or fluids down, or severe stomach pain, contact your GP immediately. Dehydration is a risk — drink regularly in small amounts. Your prescriber may adjust your dose if side effects are severe.
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.