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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Which Foods Should You Avoid When Taking Mounjaro?
When taking Mounjaro (tirzepatide), certain foods can trigger or worsen side effects like nausea, vomiting, and stomach discomfort. While there are no officially forbidden foods, understanding which foods are more likely to cause problems can help you manage symptoms and stay comfortable during treatment. This guide covers the foods most people find difficult when using this dual GIP and GLP-1 receptor agonist injection, plus practical strategies for eating well whilst on Mounjaro.
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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 Limit Or Avoid On Mounjaro
High-fat and greasy foods are often poorly tolerated on Mounjaro. These include fried foods, fatty meats, full-fat dairy, and heavy sauces, which can trigger nausea and stomach discomfort. Fat moves through your digestive system more slowly, and Mounjaro already slows gastric emptying, compounding the problem.
Spicy foods may trigger acid reflux and stomach irritation in some people, particularly if you already experience indigestion on Mounjaro. Chilli, curry, and heavily seasoned dishes are common triggers.
Sugary and ultra-processed foods can cause bloating, nausea, and energy crashes. These offer little nutritional benefit and are often harder to digest. Avoid sweets, biscuits, cakes, sugary drinks, and processed snacks.
Fibrous foods in large amounts (raw vegetables, whole grains, legumes) can cause severe bloating and constipation on Mounjaro. Include fibre gradually and in smaller portions, softly cooked rather than raw where possible.
Alcohol may worsen nausea and dizziness, and can affect blood sugar control if you have diabetes. Limit consumption and avoid drinking on an empty stomach.
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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.
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Mounjaro Vs Wegovy: Are Dietary Restrictions Different?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) work similarly on digestion—they slow how quickly food leaves your stomach and reduce appetite. Dietary restrictions are essentially the same for both medications. Trial data from SURMOUNT (Mounjaro) and STEP (Wegovy) show participants reported identical common side effects: nausea, vomiting, constipation, and diarrhoea. Both require similar food tolerance strategies.
The main difference is mechanism: Mounjaro activates both GIP and GLP-1 pathways (dual action), whilst Wegovy targets GLP-1 only. However, this doesn't meaningfully change which foods cause problems. Your GP or prescriber can advise based on your individual response, as tolerance varies considerably between people. Use our GLP-1 weight loss calculator to explore how either medication might work for you, and discuss food tolerance expectations at your clinical assessment.
Meal size and timing matter more than specific food avoidance. Eat smaller, more frequent meals rather than large portions. Space meals 3–4 hours apart to allow adequate digestion. Eat slowly and chew thoroughly—this reduces nausea significantly. Cold or room-temperature foods are often better tolerated than hot meals, particularly early on. Drink adequate water throughout the day to prevent constipation, a very common side effect. If you experience persistent nausea or vomiting, inform your prescriber—dose adjustment or anti-nausea support may help. Most people find their food tolerance improves as their body adjusts to Mounjaro, typically within 4–8 weeks at each dose level.
- 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?
Yes, but portion sizes naturally reduce because Mounjaro suppresses appetite. You'll likely feel satisfied with smaller meals. Avoid very fatty, spicy, or high-sugar foods initially, as these trigger nausea more easily. Most people gradually return to normal eating as their body adjusts, though portions remain smaller. Your GP can advise if specific foods cause problems for you personally.
What about soft foods vs hard foods on Mounjaro?
Soft, easily digestible foods are gentler on your stomach whilst taking Mounjaro. Choose mashed potatoes, scrambled eggs, soup, fish, and soft vegetables initially. Hard, crunchy, or dense foods require more stomach effort to break down, which can worsen nausea. As symptoms improve (usually after 4 weeks), you can gradually reintroduce firmer foods. Chew thoroughly regardless of texture.
Does Mounjaro mean I have to follow a specific diet?
No official Mounjaro diet exists. However, a reduced-calorie, balanced diet alongside Mounjaro and physical activity produces the best weight loss results—this mirrors the SURMOUNT clinical trials. Focus on protein and fibre for sustained fullness, and avoid empty-calorie ultra-processed foods. Your prescriber or a dietitian can create a personalised plan.
Is Mounjaro the same as Wegovy for food tolerance?
Yes, functionally. Both slow digestion and suppress appetite, causing similar food intolerances (nausea, constipation, bloating). Mounjaro uses a dual GIP+GLP-1 mechanism whilst Wegovy is GLP-1 only, but this doesn't change which foods cause problems. Individual tolerance varies—discuss specific food concerns with your prescriber during your clinical assessment.
What if I feel sick no matter what I eat on Mounjaro?
Persistent nausea is common in the first few weeks at a new dose. Try eating smaller meals more frequently, avoid hot foods, stay hydrated, and rest after eating. If nausea continues beyond 4 weeks or becomes severe, contact your prescriber—they may adjust your dose, recommend anti-nausea medication, or review whether Mounjaro is suitable for you.
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