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's the Best Diet When Taking Mounjaro?
Taking Mounjaro (tirzepatide) works best when combined with dietary changes and increased physical activity — medication alone isn't enough for sustainable weight loss. This guide explains how to structure your diet whilst on Mounjaro, manage common side effects like nausea and constipation, and avoid pitfalls that could limit your results. Whether you're accessing Mounjaro through the NHS or privately, the same nutritional principles apply. Your prescriber should provide personalised dietary advice, but understanding the fundamentals helps you make informed food choices alongside your treatment.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
Diet Strategy: What to Eat While on Mounjaro
Mounjaro works by reducing appetite and helping you feel fuller on smaller portions. This means your diet should focus on nutrient density rather than quantity — you're eating less, so each meal needs to count nutritionally.
- Prioritise protein: Aim for lean protein (chicken, fish, eggs, Greek yogurt, legumes) at every meal. Protein keeps you fuller longer and helps preserve muscle during weight loss.
- Include whole grains: Brown rice, oats, quinoa, and wholemeal bread provide sustained energy and fibre to combat constipation — a common Mounjaro side effect.
- Eat plenty of vegetables: Low-calorie, nutrient-rich vegetables (broccoli, spinach, carrots, peppers) bulk out meals without excess calories.
- Healthy fats in moderation: Olive oil, avocados, nuts, and oily fish support hormone function and nutrient absorption.
- Avoid ultra-processed foods: Sugary drinks, fast food, and highly processed snacks tend to trigger nausea on Mounjaro and offer little nutritional value.
Many people find small, frequent meals work better than three large ones whilst adjusting to Mounjaro. Eating slowly and chewing thoroughly also helps minimise stomach upset.
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.
Managing Side Effects Through Food Choices
Nausea and constipation are the most common diet-related challenges on Mounjaro. To manage nausea: eat smaller portions, avoid greasy or spicy foods, stay hydrated with water and herbal tea, and eat bland options like toast, rice, and chicken when symptoms peak. Nausea typically improves as your body adjusts to each dose over 4–8 weeks.
For constipation, increase fibre gradually through vegetables, fruits (berries, pears), whole grains, and legumes. Drink at least 2 litres of water daily — dehydration worsens constipation. If symptoms persist after dietary changes, discuss this with your GP or prescriber; they may recommend a stool softener. Use our free GLP-1 weight loss calculator to track your projected progress as your body adjusts to 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.
Should I follow a specific diet plan like keto or low-carb whilst on Mounjaro?
No specific diet is required for Mounjaro to work. A balanced, calorie-controlled diet with plenty of protein, whole grains, and vegetables is most effective. Keto or low-carb approaches aren't necessary and may increase side effects like nausea. Work with a registered dietitian if available, especially through NHS specialist weight management services.
How much should I eat per day on Mounjaro?
Mounjaro reduces your appetite, so you'll naturally eat less — typically 500–1000 kcal below your normal intake. Rather than counting strict calories, focus on eating balanced meals with protein, vegetables, and whole grains until satisfied. Your prescriber can advise on a target calorie intake based on your personal health. Use the BMI calculator on this page to track your progress over time.
Can I drink alcohol whilst taking Mounjaro?
Yes, but in moderation. Alcohol may increase nausea, especially in the first few weeks on Mounjaro. Avoid sugary cocktails and spirits on an empty stomach. Check with your prescriber if you have any health conditions or take other medications that interact with alcohol. Limit intake to within NHS guidelines (14 units per week for adults).
Is it safe to skip meals on Mounjaro because I'm not hungry?
It's safe to eat less because Mounjaro reduces appetite, but don't skip meals entirely — your body needs consistent nutrition. Eat regular, balanced meals even if portions are smaller. Skipping meals can lead to nutrient deficiencies, low energy, and muscle loss. Aim for three modest meals plus healthy snacks if needed.
What's the difference between diet advice for Mounjaro vs Wegovy?
Both are GLP-1-based weight loss medications (Mounjaro is a dual GIP/GLP-1 agonist, Wegovy is GLP-1 only), and the dietary approach is almost identical: balanced nutrition, adequate protein, plenty of vegetables, smaller portions, and hydration. Any differences are individual, not medication-specific. Your prescriber will give personalised dietary guidance regardless of which medication you're prescribed.
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.