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
How to Prevent Muscle Loss on Mounjaro
Mounjaro (tirzepatide) is a prescription-only weekly weight loss injection that may help you lose weight, but like all gradual weight management methods, it can lead to muscle loss alongside fat loss. Protecting your lean muscle mass during treatment is essential for maintaining metabolism, strength, and overall health. The good news: specific strategies can significantly reduce muscle loss whilst you use Mounjaro. This guide covers evidence-based approaches recommended by UK healthcare professionals.
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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.
Protein, Resistance Training, and Lifestyle During Mounjaro Treatment
Protein intake is the foundation of muscle preservation. Aim for at least 1.6–2.2 grams of protein per kilogram of body weight daily — higher than standard recommendations. This supports muscle protein synthesis, especially important when you're in a calorie deficit. Distribute protein across meals rather than loading it into one meal. Good sources include chicken, fish, eggs, Greek yoghurt, pulses, and lean beef.
Resistance training is non-negotiable. Strength training twice weekly (or more) signals your body to preserve muscle during weight loss. Focus on compound movements: squats, deadlifts, chest presses, and rows. You don't need to lift heavily — moderate resistance with good form is sufficient. If you're new to resistance training, ask your GP for a referral to a physiotherapist or personal trainer who can design a safe programme.
Stay hydrated and manage side effects. Mounjaro causes nausea and reduced appetite in many users, which can make it harder to eat enough protein. Eat small, frequent meals and stay hydrated. If nausea is severe, discuss this with your prescriber — your dose may need adjusting.
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.
Monitoring Muscle Loss and Working With Your Healthcare Team
It's difficult to measure muscle loss at home, but you can track indicators: weigh yourself weekly (use our free progress tracker to log results), take body measurements (waist, chest, thighs), and notice how your clothes fit. If you're losing more than 1 kg per week consistently, you may be losing muscle faster than ideal — discuss this with your GP or the prescriber managing your Mounjaro treatment. They may suggest slowing your dose escalation or adjusting your calorie deficit.
Consider a dexa scan or bioelectrical impedance analysis (BIA) if available through your NHS weight management service or privately. These measure body composition directly, showing how much fat versus muscle you're losing. This data helps your healthcare team optimise your treatment plan to preserve lean mass.
- 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 do I need whilst on Mounjaro?
Aim for 1.6–2.2 grams of protein per kilogram of body weight daily. If you weigh 80kg, that's approximately 128–176g of protein daily. This is higher than standard recommendations because you're in a calorie deficit. Distribute it across meals — aim for 25–35g per meal.
Does resistance training interfere with weight loss on Mounjaro?
No. Resistance training does not reduce weight loss from Mounjaro — it simply preserves muscle mass whilst you lose fat. You may lose weight slightly more slowly than someone not exercising, but you'll have better body composition (less muscle loss). This is healthier long-term.
Can my GP help me manage muscle loss whilst on Mounjaro?
Yes. If you're prescribed Mounjaro through NHS specialist weight management services, your care team can monitor your progress and advise on protein and exercise. If you're using a private prescription, ask your prescriber about access to a dietitian or exercise specialist for personalised muscle-preservation strategies.
What if I struggle to eat enough protein due to Mounjaro nausea?
Nausea is a common side effect. Try small, frequent meals; protein shakes; Greek yoghurt; and soup-based meals that are easier to tolerate. If nausea is severe and affecting nutrition, tell your prescriber — your dose might need adjustment or a slower escalation between strength levels.
How quickly should I be losing weight on Mounjaro to avoid excess muscle loss?
The NHS recommends losing 0.5–1 kg per week for sustainable weight loss with minimal muscle loss. If you're losing more than 1–1.5 kg weekly consistently, discuss this with your GP or prescriber — you may need to increase calories slightly or adjust your Mounjaro dose to preserve lean mass.
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.