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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Mounjaro and Protein Intake — What You Need to Know
When taking Mounjaro (tirzepatide), adequate protein intake becomes particularly important. Mounjaro reduces appetite and slows how quickly food leaves your stomach, which can make it harder to eat enough. Getting sufficient protein helps preserve muscle mass during weight loss, supports satiety, and maintains your body's essential functions. This guide explains NHS-aligned protein recommendations for people using Mounjaro in the UK, and how to manage dietary needs as your body adjusts to treatment.
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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.
Why Protein Matters on Mounjaro
Mounjaro works by activating GIP and GLP-1 receptors, which reduces hunger signals and helps you feel fuller after smaller meals. However, this appetite suppression means you may eat significantly less than before — which increases the risk of inadequate protein intake.
- Muscle preservation: Without enough protein, your body breaks down muscle tissue during weight loss, which slows your metabolism and makes long-term weight management harder.
- Satiety and fullness: Protein is more satiating than carbohydrates or fats, helping you feel satisfied despite eating less.
- Recovery and immunity: Protein supports immune function, wound healing, and overall health during weight loss.
- Blood sugar stability: Adequate protein helps stabilise blood glucose, which complements Mounjaro's action and may improve energy levels.
The NHS recommends adults consume 0.8g of protein per kilogram of body weight daily — and this baseline applies whether you're using Mounjaro or not. However, during active weight loss, many health professionals recommend slightly higher intake (1.0–1.2g/kg) to protect muscle mass.
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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.
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Practical Protein Strategies While on Mounjaro
Prioritise protein at every meal: Because your appetite is reduced, make protein your priority — eat protein first, then add vegetables and carbohydrates as hunger allows. This maximises nutritional density in smaller meal volumes.
- Choose high-protein foods: Lean chicken, fish, eggs, Greek yoghurt, cottage cheese, legumes, and plant-based proteins like tofu and tempeh.
- Use protein supplements if needed: Protein shakes or powder can make it easier to meet targets when solid food feels difficult to tolerate.
- Spread intake throughout the day: Aim for 25–30g protein per meal rather than loading all protein into one sitting.
- Monitor how you feel: Use MyWeightCheck's free progress tracker to log your meals, energy levels, and how different protein sources make you feel on Mounjaro.
If you're unsure whether your protein intake is adequate, discuss this with your GP or a dietitian — they can assess your individual needs based on your weight, activity level, and weight loss goals.
- 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.
How much protein should I eat on Mounjaro?
The NHS baseline is 0.8g per kilogram of body weight daily. During active weight loss on Mounjaro, many health professionals recommend 1.0–1.2g/kg to preserve muscle mass. For example, at 80kg, aim for 80–96g protein daily. Your GP or a dietitian can give personalised recommendations based on your individual health and activity level.
What happens if I don't eat enough protein on Mounjaro?
Insufficient protein during weight loss increases muscle loss, which slows your metabolism and makes maintaining weight loss harder long-term. You may also experience fatigue, weaker immune function, and slower recovery from illness. Prioritising protein helps preserve muscle while losing fat.
Does Mounjaro make it harder to eat enough protein?
Yes. Mounjaro's appetite-suppressing effects mean you may feel full on smaller meals, making it challenging to consume adequate calories and protein. Choosing protein-rich foods, spreading protein across meals, and using supplements can help you meet targets despite reduced appetite.
Can I use protein shakes on Mounjaro?
Yes, protein shakes are often helpful on Mounjaro, especially if solid food feels difficult. They're a convenient way to meet protein targets when appetite is low. Choose shakes without excessive sugar, and discuss with your GP if nausea or other side effects persist.
Should I exercise more to preserve muscle on Mounjaro?
Resistance exercise (strength training) combined with adequate protein is most effective for preserving muscle during weight loss. Even light resistance work — such as bodyweight exercises or light weights — helps signal your body to maintain muscle. Discuss any exercise plans with your GP to ensure they're appropriate for you.
Ready to take control of your weight loss journey?
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