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
Does Mounjaro Affect Your Liver?
Mounjaro (tirzepatide) is a prescription-only weight management injection licensed in the UK. You may be wondering whether this medication affects liver function. The good news is that clinical trials and post-market monitoring have not identified liver damage as a direct side effect of Mounjaro. However, your GP or prescriber may recommend liver function tests before starting treatment, particularly if you have existing liver disease or take medications that affect the liver. This is a standard safety precaution for many prescription medications. If you have concerns about your liver health, discuss them with your prescriber during your clinical assessment.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
Liver Safety and Mounjaro Monitoring in the UK
Mounjaro has not been shown to cause liver damage in clinical trials or post-market monitoring data. However, your prescriber may check your liver function before starting the medication, especially if you have risk factors for liver disease. Liver function tests (LFTs) measure how well your liver is working and typically include checks for enzymes like ALT and AST, as well as bilirubin levels.
If you have non-alcoholic fatty liver disease (NAFLD) or other liver conditions, inform your prescriber during your clinical assessment. Weight loss itself often improves liver health by reducing fat stored in the liver — a benefit many people experience when using GLP-1 medications like Mounjaro alongside lifestyle changes. Your GP can advise whether Mounjaro is appropriate for your individual liver health status. Regular monitoring may be recommended if you have existing liver disease, though this varies based on your clinical history.
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.
Accessing Mounjaro in the UK and Clinical Safety Assessment
Mounjaro is available in the UK through two routes: NHS specialist weight management services or private online prescription services. Both routes involve a clinical assessment where your prescriber will review your full medical history, including any liver conditions or medications you take. This assessment ensures Mounjaro is safe for you personally.
NHS access is through tier 3 specialist services following GP referral, though waiting lists vary significantly by region. Private access is through GPhC-registered online pharmacies following an online consultation with a UK-licensed prescriber. During either assessment, you'll be asked about your liver health and any medications affecting the liver. Use our free GLP-1 weight loss calculator to understand potential weight loss benefits, and discuss all safety concerns with your prescriber before starting treatment.
- 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.
Can Mounjaro cause liver disease?
No. Clinical trials and post-market monitoring have not identified liver damage as a direct side effect of Mounjaro. However, if you have existing liver disease, inform your prescriber so they can assess whether the medication is appropriate for you and recommend monitoring if needed.
Will my prescriber check my liver before starting Mounjaro?
Your prescriber may recommend liver function tests as a standard safety precaution, particularly if you have risk factors for liver disease or take medications affecting the liver. This is part of the clinical assessment process and helps ensure Mounjaro is safe for you individually.
Does weight loss from Mounjaro help or harm the liver?
Weight loss generally improves liver health, especially for people with fatty liver disease (NAFLD). Many people experience improvement in liver health as they lose weight using Mounjaro alongside diet and exercise, provided the weight loss is achieved at a safe, sustainable rate.
What if I have hepatitis or fatty liver disease?
Inform your prescriber during your clinical assessment about any liver conditions. They will review whether Mounjaro is appropriate for you and may recommend liver function monitoring. You should not start Mounjaro without discussing your liver health with a qualified healthcare professional.
How do I access Mounjaro safely in the UK?
Access Mounjaro through either an NHS tier 3 specialist service (by GP referral) or a private online prescriber following a clinical assessment. Both routes involve health screening to ensure the medication is safe for you. Never obtain Mounjaro without a prescription from a UK-licensed prescriber.
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.