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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Creatine and Mounjaro — What You Need to Know
If you're considering or currently taking Mounjaro (tirzepatide) and wondering whether creatine supplementation is safe, this guide covers the key interactions and considerations. Mounjaro is a prescription-only, once-weekly injection used for weight management in UK adults, and combining it with supplements like creatine requires careful thought. While there is no direct contraindication, understanding how both work and their combined effects is important for making informed decisions about your health.
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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 and Creatine Work Together
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist that helps regulate appetite and supports weight loss alongside dietary changes and physical activity. It works by slowing gastric emptying and reducing food cravings. Creatine is an amino acid derivative that supports muscle energy production and may help preserve muscle mass during weight loss.
There is no direct pharmacological interaction between Mounjaro and creatine — they work through different biological pathways. However, several practical considerations apply:
- Mounjaro may reduce overall calorie intake, which could affect creatine supplementation effectiveness
- Gastrointestinal side effects from Mounjaro (nausea, constipation) may impact supplement absorption
- Creatine requires adequate hydration to work effectively — Mounjaro can affect fluid intake patterns
- Clinical evidence for creatine's muscle-preserving effects during GLP-1 use is limited
Always discuss any supplements with your prescriber or GP before starting, especially if you have kidney concerns or take other medications.
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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.
Muscle Loss and Weight Loss Medications
When using Mounjaro or other weight loss medications, some muscle loss can occur alongside fat loss — this is a recognised concern with gradual weight management. Creatine supplementation may help, but evidence specific to GLP-1 or GIP/GLP-1 users is limited. Resistance exercise is the most effective way to preserve muscle mass during weight loss. Combine Mounjaro with regular strength training and adequate protein intake (approximately 1.6–2.2g per kg of body weight daily) for best results. Use our free GLP-1 weight loss calculator to project realistic outcomes with Mounjaro, and consult your GP or a registered dietitian about whether creatine is appropriate for your specific situation and medical history.
- 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.
Is creatine safe to take while on Mounjaro?
There is no direct pharmacological interaction between creatine and Mounjaro, so they are generally considered safe together. However, inform your prescriber or GP before starting any supplement, especially if you have kidney concerns or medical conditions. Individual circumstances vary — professional guidance is essential.
Will creatine help preserve muscle mass on Mounjaro?
Creatine may support muscle preservation during weight loss, but clinical evidence specific to Mounjaro users is limited. Resistance exercise is the most effective approach. Adequate protein intake (1.6–2.2g per kg daily) combined with strength training is key to maintaining muscle during weight loss.
Can Mounjaro's side effects affect creatine absorption?
Yes, potentially. Mounjaro can cause nausea, constipation, and changes in appetite, which may affect how supplements are absorbed. Adequate hydration is essential for creatine effectiveness, and Mounjaro may influence fluid intake patterns. Monitor how you feel and discuss any concerns with your GP.
Should I start creatine before or during Mounjaro treatment?
There is no established timing rule. Starting before, during, or after Mounjaro is acceptable from an interaction perspective. However, consult your prescriber first, especially if you're managing any kidney function concerns or taking other medications. Professional guidance personalised to your health is important.
Is creatine appropriate for all Mounjaro users?
Not necessarily. Creatine is contraindicated in individuals with kidney disease, kidney function concerns, or certain medical conditions. If you're eligible for Mounjaro, discuss supplement use with your GP or prescriber. Use our BMI calculator and weight converter to understand your starting point, then seek personalised dietary and supplement advice from a registered dietitian.
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.