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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Diet Plan for Mounjaro — What Works in the UK
If you're starting Mounjaro (tirzepatide) on the NHS or privately in the UK, diet planning is essential for successful weight management. Mounjaro works best alongside a reduced-calorie diet and increased physical activity — medication alone won't deliver results. This guide covers NHS nutrition guidance, practical meal planning, foods to prioritise, and how your diet should adapt as you progress through dose titration. Whether you're accessing Mounjaro through a tier 3 NHS specialist service or private prescription, understanding how to eat alongside this injection is crucial for safety and effectiveness.
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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.
How Mounjaro Changes Your Appetite and Eating
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist that directly affects hunger signals. Most people on Mounjaro experience reduced appetite, smaller portion sizes feeling satisfying, and fewer food cravings — especially for high-fat and high-sugar foods. This isn't willpower; it's a physiological change. However, this means your diet must adapt to prevent nutritional deficiencies.
Key dietary changes most people need:
- Smaller portions — your stomach will feel full sooner
- Protein focus — aim for 25–30g per meal to preserve muscle during weight loss
- Stay hydrated — drink 2–3 litres of water daily, as Mounjaro can cause constipation and nausea
- Avoid high-fat foods — these can trigger nausea and stomach discomfort (GI side effects are common)
- Limit sugary drinks — they provide calories without satiety signals
Your appetite suppression will be strongest in the first 4–8 weeks, then may stabilise slightly as your body adapts. This is normal. Use our free GLP-1 weight loss calculator to project realistic outcomes based on your current weight and dose.
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.
NHS Nutrition Guidance and Tier 3 Services
If you're accessing Mounjaro through an NHS tier 3 specialist weight management service, you should receive support from a dietitian or nutrition specialist as part of your care pathway. The NHS recommends a balanced, reduced-calorie diet alongside medication — typically a 500 kcal daily deficit for sustainable weight loss of approximately 0.5–1 kg per week. However, many NHS services have long waiting lists, and dietitian appointments may be limited.
NHS-approved diet frameworks include the Mediterranean diet (high in vegetables, fish, and healthy fats) and the DASH diet (designed for heart health). Both support sustainable weight loss and work well with Mounjaro. If you're on the NHS, ask your GP or specialist service for a referral to dietitian support. If you're on a private prescription, consider booking a consultation with a registered dietitian nutritionist (RD or RDN credential) to create a personalised meal plan aligned with your Mounjaro doses and side 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.
What should I eat in the first week starting Mounjaro?
Start with soft, easily digestible foods — scrambled eggs, porridge, soup, cooked vegetables, lean chicken, and low-fat yoghurt. Avoid fried foods, high-fat meats, and spicy dishes. Eat slowly and chew thoroughly. Stay hydrated with water and herbal tea. Many people have mild nausea initially, so small frequent meals work better than large ones.
Can I follow a specific diet like keto or intermittent fasting with Mounjaro?
Very restrictive diets are not recommended with Mounjaro. Your reduced appetite is already significant — combining this with extreme restriction risks malnutrition and muscle loss. Instead, follow a balanced, moderate deficit diet. If considering intermittent fasting, discuss it with your GP or prescriber first, especially if you take other medications.
How much weight will I lose following a good diet plan on Mounjaro?
Clinical trials (SURMOUNT-1) showed average weight loss of 15–21% body weight at the maximum dose, alongside reduced-calorie diet and increased activity. Individual results vary significantly based on starting weight, metabolism, adherence, and genetics. Use our BMI calculator and weight loss calculator to establish your baseline and track progress realistically.
What if I have nausea or can't eat much on Mounjaro — is that dangerous?
Mild nausea is common, especially during dose titration. However, severe nausea lasting more than a few days is not normal. Contact your GP or prescriber. Ensure you're still meeting protein needs — try protein shakes, Greek yoghurt, or soup. If you feel dizzy, weak, or unwell, seek medical advice. Never skip meals entirely.
Should I count calories on Mounjaro, or does the appetite suppression do it for me?
Appetite suppression helps, but calorie awareness is still important. Some people overeat despite feeling fuller, or choose very calorie-dense foods. Tracking intake loosely (even via a food diary app) helps you understand patterns and ensures you're in a true deficit. Your prescriber or dietitian can advise on realistic calorie targets for your weight and health.
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.