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 Can't You Eat On Mounjaro?
Mounjaro (tirzepatide) doesn't restrict specific foods, but how your body tolerates different foods may change significantly. Most people find their appetite naturally decreases and portion sizes reduce. However, certain foods become harder to tolerate — particularly fatty, greasy, or heavily processed foods that can trigger nausea or stomach discomfort. Understanding these changes helps you work with Mounjaro more effectively and avoid digestive side effects. Your GP can provide personalised guidance alongside the medication.
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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 Likely to Cause Problems On Mounjaro
While Mounjaro doesn't ban specific foods, many people find their tolerance changes dramatically. High-fat and greasy foods — including fried foods, fatty cuts of meat, creamy sauces, and full-fat dairy — often trigger nausea or stomach upset. Large meals become difficult to manage because Mounjaro slows how quickly food leaves your stomach and increases feelings of fullness. Spicy foods may cause indigestion or reflux in some people. Sugary foods and drinks can cause nausea in early weeks.
- Fried takeaways and fast food
- High-fat meats and processed meats
- Rich desserts and full-fat ice cream
- Alcohol — particularly on an empty stomach
- Very large portions of any food
The good news is that as your body adjusts and you stabilise on a higher Mounjaro dose, some tolerance may improve. Individual responses vary significantly. Our GLP-1 weight loss calculator can help you understand how dietary changes combine with medication to support weight management.
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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 Usually Work Better On Mounjaro
Lean proteins, vegetables, and whole grains tend to be much better tolerated. Lean poultry, fish, eggs, and plant-based proteins sit well with most people. Vegetables — both cooked and raw — are often easier on the stomach than fatty foods. Whole grains, low-fat yoghurt, and plenty of water support both medication tolerance and weight loss.
- Grilled chicken, turkey, and fish
- Vegetables (broccoli, spinach, carrots)
- Whole grains and brown rice
- Low-fat proteins and legumes
- Plenty of water and sugar-free drinks
Eating smaller, more frequent meals rather than three large meals per day works better with how Mounjaro affects your stomach. Track your weight loss progress with our free progress tracker to see how dietary adjustments combine with the medication's effects.
- 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 portion sizes and food tolerance often change significantly. Most people naturally eat much less because Mounjaro increases fullness signals. Fatty and greasy foods become harder to tolerate, so you may find yourself preferring lighter options naturally.
Does Mounjaro forbid any specific foods?
No. Mounjaro (tirzepatide) doesn't medically forbid any foods, but your body's tolerance may change. High-fat, fried, and very large meals are most likely to cause nausea or stomach discomfort. This is a side effect of how the medication works, not a dietary rule.
What if I feel nausea when eating certain foods?
Nausea is a very common side effect, especially in early weeks. Avoid the foods triggering it and focus on smaller portions of lean proteins, vegetables, and whole grains. Stay hydrated. If nausea is severe or persistent, contact your GP — they may adjust your dose or offer additional support.
Can I drink alcohol on Mounjaro?
Alcohol is possible but requires caution. Alcohol on an empty stomach increases nausea risk significantly. Small amounts with food may be tolerated better. Your prescriber can give personalised guidance based on your individual health.
How does diet work with Mounjaro for weight loss?
Mounjaro reduces appetite and increases fullness, which naturally leads to eating less. For best results, combine this with a balanced, reduced-calorie diet and physical activity. Your GP or a registered dietitian can provide a personalised eating plan. Use our GLP-1 weight loss calculator to understand projected results with dietary changes.
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.