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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How Much Protein Should I Have on Mounjaro?
When taking Mounjaro (tirzepatide), protein intake becomes particularly important because the medication reduces appetite and slows stomach emptying, which can affect how much food you eat overall. Most UK health guidance suggests adults on Mounjaro should aim for higher protein relative to their total calorie intake to preserve muscle mass during weight loss. Your GP or prescriber can give personalised advice based on your individual health, but this guide covers the general evidence-based principles.
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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.
Protein Needs on Mounjaro — The Evidence
When you're losing weight on Mounjaro, your body uses both fat and muscle for energy. Adequate protein helps protect lean muscle mass, which is crucial because muscle supports metabolism, strength, and overall health. General guidance suggests 1.2 to 1.6 grams of protein per kilogram of body weight daily during active weight loss — roughly 20–30% of your total daily calories.
- At lower body weights (60–70 kg), this means approximately 70–110 grams of protein daily
- At higher body weights (90–110 kg), aim for 110–160 grams daily
- Distribute protein across all meals to support muscle synthesis
Because Mounjaro reduces appetite significantly, many UK patients find it challenging to eat enough food, let alone hit protein targets. This is where deliberate food choices matter — prioritising protein-rich, nutrient-dense foods helps you meet your protein needs on smaller portions. Working with a registered dietitian can help you create a realistic plan tailored to your appetite and preferences.
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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 Sources on Mounjaro
When appetite is reduced on Mounjaro, choosing calorie-efficient protein sources helps you meet targets without overeating. High-protein foods that work well include:
- Eggs and Greek yoghurt (protein-dense, easy to digest)
- Lean poultry, fish, and seafood (low fat, nutrient-rich)
- Lentils and legumes (protein plus fibre)
- Cottage cheese and cheese (concentrated protein)
- Protein powder or shakes (convenient, especially if nausea affects appetite)
Some people on Mounjaro experience nausea or food aversions, particularly in the first weeks at each dose increase. If solid protein feels difficult, protein shakes, Greek yoghurt, or soup-based dishes may be easier to tolerate. Stay hydrated and eat slowly — Mounjaro slows gastric emptying, so rushing meals can worsen nausea.
- 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 happens to muscle on Mounjaro if I don't eat enough protein?
gradual weight management without adequate protein increases muscle loss, which slows metabolism and can make weight regain more likely. Protein preserves lean mass during the weight loss phase, supporting long-term metabolic health and strength.
Can I track my protein intake using standard apps?
Yes — MyFitnessPal, Cronometer, and similar UK-compatible apps let you log meals and monitor daily protein intake against your target. This is especially useful on Mounjaro because appetite suppression can lead to unintentionally low calorie and protein intake.
Is 1.6g of protein per kg essential, or can I do with less?
General weight loss guidance recommends 1.2–1.6g/kg. Some research supports lower intakes (0.8–1.2g/kg) if you're not doing strength training, but higher protein is protective during gradual weight management. Your GP or dietitian can advise what's right for your situation.
Should I use protein powder on Mounjaro, or get protein from whole foods?
Both work. Whole foods provide additional nutrients and fibre, but protein powder is convenient when nausea affects appetite — which is common on Mounjaro, especially during dose increases. A mix of both is often practical.
Does Mounjaro itself affect protein digestion or absorption?
Mounjaro slows how quickly food leaves your stomach (gastric emptying), which may temporarily affect how fast protein is digested. However, it doesn't prevent protein absorption. Eating slowly and chewing well helps. If you have concerns, discuss with your GP.
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