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 Kidney Disease — What You Need to Know
If you have kidney disease and are considering Mounjaro (tirzepatide) for weight management, it's important to understand how this medication interacts with kidney function. Mounjaro is a prescription-only GLP-1 and GIP receptor agonist approved in the UK for weight management in adults. However, kidney function affects how medications are processed in your body, so your prescriber needs to assess your individual situation before deciding if Mounjaro is safe and appropriate for you. This guide explains the key considerations, eligibility criteria, and how to access treatment in the UK.
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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.
Mounjaro, Kidney Function, and Safety Considerations
Mounjaro has not been extensively studied in people with severe kidney disease, which means prescribers approach it cautiously in this group. Your kidney function is measured by eGFR (estimated glomerular filtration rate), and this measurement is crucial when assessing whether weight loss medications are safe for you.
- Mild kidney disease (eGFR 60–89): Mounjaro may be considered, but requires careful monitoring
- Moderate kidney disease (eGFR 30–59): Prescribers typically require closer assessment and may recommend caution or alternative treatments
- Severe kidney disease (eGFR below 30) or on dialysis: Mounjaro is generally not recommended without specialist renal input
Additionally, GLP-1 medications like tirzepatide can affect blood pressure and blood sugar levels, both of which are particularly important to monitor in people with kidney disease. Dehydration risk is also higher with GLP-1 use, especially if you experience nausea or vomiting — and dehydration can worsen kidney function. Your GP or prescriber will need to review your kidney function tests (eGFR and creatinine) before prescribing.
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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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Accessing Mounjaro in the UK When You Have Kidney Disease
If you have kidney disease and want to explore weight loss treatment, your first step is discussing this with your GP or renal specialist. NHS access is through specialist tier 3 weight management services, often in collaboration with renal teams to ensure safe prescribing. Private prescription routes require an online consultation with a UK-licensed prescriber who will assess your kidney function and medical history before issuing a prescription.
Both routes require recent blood tests showing your kidney function. Be honest about your kidney condition — prescribers need this information to decide if Mounjaro is appropriate or if alternative options like dietary support, exercise programmes, or other medications might be safer. The cost of private Mounjaro varies by dose (typically £150–£300 per month), but this is only relevant if a prescriber confirms it's safe for your individual situation.
- 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 I take Mounjaro if I have kidney disease?
It depends on how advanced your kidney disease is. Mounjaro may be considered with mild kidney disease but requires careful prescriber assessment. With moderate or severe kidney disease, it's generally not recommended without specialist renal input. Always discuss with your GP or renal specialist first — they can review your kidney function tests and advise whether it's safe.
What kidney tests do I need before taking Mounjaro?
Your prescriber will need recent blood tests showing your eGFR (estimated glomerular filtration rate) and creatinine levels. These measure how well your kidneys are filtering waste. You should have these tests done within 3 months of starting Mounjaro. If you don't have recent results, your GP can arrange them.
Does Mounjaro damage kidneys or make kidney disease worse?
Mounjaro is not known to damage healthy kidneys. However, it can indirectly affect kidney function through dehydration, blood pressure changes, and blood sugar effects — which is why monitoring is essential if you have existing kidney disease. This is why prescriber assessment is critical.
How do I access Mounjaro on the NHS if I have kidney disease?
Request a referral from your GP to a specialist tier 3 weight management service. Many services now work with renal teams to assess safety. NHS access is slower and availability varies by region, but it's free. Private routes are faster but require a prescription from a UK-licensed prescriber following an online consultation.
What alternatives to Mounjaro exist for weight loss with kidney disease?
Your GP or renal specialist may recommend dietary support, structured exercise programmes, or diabetes medications that are safer with kidney disease. Some people benefit from tier 3 NHS services that provide multidisciplinary support. Always get specialist advice before starting any weight loss treatment if you have kidney disease.
Ready to take control of your weight loss journey?
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