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
Mounjaro and Creatinine — What UK Patients Need to Know
Creatinine is a waste product filtered by your kidneys, and kidney function is an important consideration before starting Mounjaro (tirzepatide). If you're being assessed for this prescription weight management injection through an NHS specialist service or private prescriber, your kidney function will typically be checked beforehand. Understanding the relationship between Mounjaro and creatinine levels can help you have informed discussions with your GP or prescriber about whether this medication is right for you.
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.
How Mounjaro Affects Kidney Function and Creatinine Levels
Mounjaro is a dual GIP and GLP-1 receptor agonist licensed in the UK for weight management. While the medication itself does not directly damage the kidneys, weight loss itself can lead to changes in kidney function, and people with existing kidney problems require careful monitoring.
Creatinine is measured in your blood as a marker of kidney function. A basic metabolic panel checking creatinine and estimated glomerular filtration rate (eGFR) is a standard pre-treatment assessment for Mounjaro. Your prescriber will:
- Check your baseline creatinine and eGFR before starting
- Confirm whether you have any history of kidney disease or reduced kidney function
- Consider whether Mounjaro is appropriate for your kidney health status
- Arrange follow-up monitoring if you have existing kidney concerns
People with severe kidney disease (eGFR below 15 mL/min/1.73m²) may not be suitable candidates for Mounjaro, and prescribers must assess individual risk.
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.
NHS Monitoring and Safe Use of Mounjaro with Kidney Function
If you're prescribed Mounjaro through an NHS tier 3 specialist weight management service, your kidney function will be monitored as part of routine care. Your GP may also check creatinine and eGFR periodically, especially if you have risk factors like type 2 diabetes or high blood pressure.
During gradual weight management with Mounjaro, your kidney function may temporarily shift — this is often normal, but your prescriber will interpret your results in context. Always inform your healthcare team if you:
- Notice changes in urine output or colour
- Develop swelling in feet or ankles
- Experience unusual fatigue or shortness of breath
- Have a history of kidney problems
Your GP can provide personalised guidance based on your individual kidney health 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.
Will Mounjaro damage my kidneys?
Mounjaro itself does not directly damage kidneys. However, kidney function is monitored before and during treatment because weight loss can affect kidney function, and people with existing kidney disease require careful assessment. Your prescriber will check your baseline kidney function before starting tirzepatide.
What creatinine level means I cannot take Mounjaro?
There is no absolute creatinine cut-off, but prescribers assess eGFR (estimated glomerular filtration rate) as the primary marker. Severe kidney disease (eGFR below 15) may mean Mounjaro is unsuitable. Your individual risk is assessed by your healthcare provider based on all factors.
How often is kidney function checked while on Mounjaro?
Monitoring frequency depends on your baseline kidney function and NHS tier 3 service protocols. If you have normal kidney function, routine checks may occur annually or as part of general health monitoring. People with existing kidney concerns will have more frequent assessments — your prescriber will advise.
Can Mounjaro be used safely if I have diabetes and kidney problems?
People with both type 2 diabetes and reduced kidney function can sometimes use Mounjaro, but this requires careful individual assessment by your prescriber. Your GP or specialist will weigh the benefits of weight loss against kidney health risks and arrange appropriate monitoring.
What should I tell my GP before starting Mounjaro?
Inform your GP if you have any history of kidney disease, reduced kidney function, diabetes, high blood pressure, or if you take medications affecting kidney function. Be honest about all health conditions — this helps your prescriber assess whether Mounjaro is safe for you and arrange appropriate monitoring. ```
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.