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 Foods Should You Avoid When Taking Mounjaro?
When you start Mounjaro (tirzepatide), certain foods can trigger or worsen common side effects like nausea, stomach pain, and digestive issues. Understanding which foods to avoid during your treatment can help you feel better and stay on track with your weight management plan. This guide covers practical dietary changes to support your Mounjaro journey, alongside clinical advice from your prescriber. Always consult your GP if side effects persist or become severe.
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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 Trigger Mounjaro Side Effects
Mounjaro works by slowing how quickly food moves through your stomach and reducing appetite — this can make certain foods harder to tolerate, especially during the first few weeks of treatment. High-fat and fried foods are often the first to cause problems: they sit heavily in the stomach and can trigger nausea, bloating, and digestive discomfort. Greasy takeaway, cream-based sauces, butter-laden pastries, and deep-fried items should be limited or avoided entirely in the early weeks.
Sugary and overly sweet foods can cause bloating and stomach cramps, and may counteract your weight loss efforts. This includes sweets, fizzy drinks, desserts, and processed snacks. High-fibre foods in large quantities — like beans, lentils, bran cereals, and raw vegetables — can initially worsen constipation or diarrhoea; introduce them gradually and drink plenty of water. Alcohol should be consumed sparingly; it can increase nausea and dehydration. Large meals are often poorly tolerated — instead, eat smaller, frequent portions to help your digestive system adjust.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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 and Managing Access
Focus on small portions of lean proteins, plain vegetables, wholegrain carbohydrates, and low-fat dairy to support tolerance and weight loss. Stay hydrated by drinking water regularly throughout the day. If you're accessing Mounjaro through a UK private online consultation, your prescriber should provide dietary guidance tailored to your dose and response. NHS specialist weight management services also offer nutritional support when Mounjaro is prescribed through the NHS tier 3/4 pathway, though waiting times vary significantly by region. Track your dietary changes and symptom improvements using our free progress tracker to identify which foods work best for your body. Always report persistent digestive issues to your prescriber so your Mounjaro KwikPen dose can be adjusted if needed.
- 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.
What's the best diet to follow while on Mounjaro?
A diet of small, frequent meals with lean proteins, vegetables, and wholegrains works best. Avoid high-fat, fried, and sugary foods initially. Drink plenty of water. Everyone's tolerance is different — your prescriber or a dietitian can give personalised advice based on your dose and side effects.
Can I eat normally on Mounjaro?
Most people find their appetite naturally reduces, so normal portion sizes feel too large. Start with smaller meals and eat slowly. As your body adjusts to Mounjaro dose titration, you may tolerate more varied foods, but high-fat foods often remain difficult throughout treatment.
Does Mounjaro vs Wegovy have different dietary requirements?
Both work similarly — they slow gastric emptying and reduce appetite. Dietary tolerance is comparable between the two. Individual responses vary, so what triggers symptoms in one person may not affect another.
Will my prescriber give me dietary advice on the UK prescription?
Yes. Private online consultations include guidance on managing side effects and diet. NHS specialist services provide more detailed nutritional support, though availability depends on your local integrated care board.
How long until I can eat normally on Mounjaro?
Many people tolerate regular foods better after 4–8 weeks as their body adjusts. However, high-fat foods may always cause discomfort. Work with your prescriber to gradually reintroduce foods and monitor your individual response.
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.