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 (Tirzepatide) — NHS UK Information Guide
Mounjaro (tirzepatide) is a prescription-only GLP-1 and GIP receptor agonist licensed in the UK for weight management in adults. This guide explains how Mounjaro works, who may be eligible through NHS specialist services or private prescribing, and what the clinical evidence shows. Unlike single-action medications, Mounjaro activates two natural hormone pathways to help regulate appetite and support weight loss alongside diet and activity changes. Whether you're exploring options through your GP or researching private access, understanding the UK prescribing landscape helps you make 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.
NHS Eligibility and Access Routes for Mounjaro in the UK
NHS access to Mounjaro is through specialist tier 3 and tier 4 weight management services, not routine GP prescription. NICE has approved tirzepatide for use within NHS specialist services for adults with a BMI of 30 kg/m² or above, or BMI 27–29.9 kg/m² with weight-related health conditions such as type 2 diabetes, hypertension, dyslipidaemia, or obstructive sleep apnoea.
For South Asian, Chinese, Black African, or Black Caribbean adults, lower thresholds apply (BMI 27.5 or above for obesity category) due to higher cardiovascular risk at lower weights. NHS access varies significantly by region and integrated care board (ICB). Waiting lists for tier 3 services can be lengthy in many areas — some regions have waiting times of several months to over a year.
Your GP can refer you to your local specialist weight management service if you meet clinical criteria. The service will conduct a full assessment before prescribing, including review of your medical history, current medications, and suitability for the weekly weight loss injection. Use our free BMI calculator to check your starting point before speaking to your GP.
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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.
Private Access and Clinical Trial Evidence for Mounjaro
Private prescribing offers faster access to Mounjaro without NHS referral. UK-licensed prescribers can issue prescriptions following an online clinical assessment, which are then dispensed by GPhC-registered pharmacies. The SURMOUNT-1 clinical trial demonstrated that Mounjaro helped participants lose an average of 15–21% of their body weight over 72 weeks when combined with reduced-calorie diet and increased physical activity — though individual results vary significantly.
Monthly costs range from approximately £129 to £320 depending on the dose (2.5 mg to 15 mg weekly). Mounjaro is supplied as a KwikPen pre-filled device with four weekly injections per pen. Both routes — NHS and private — require a clinical assessment to confirm suitability. Try our GLP-1 weight loss calculator to estimate potential outcomes at different doses.
- 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.
What is the difference between Mounjaro and Wegovy?
Both are prescription weight loss injections, but Mounjaro (tirzepatide) activates GLP-1 and GIP receptors, while Wegovy (semaglutide) activates GLP-1 only. Clinical trial data suggests Mounjaro may produce slightly greater average weight loss (15–21% vs ~15%), though results vary individually. Both are once-weekly injections and both require prescription and clinical assessment.
How long does it take to access Mounjaro through the NHS?
NHS access depends on your regional ICB. You'll need a GP referral to specialist tier 3 weight management services. Waiting times vary from weeks to over a year in some areas. Private prescribing is typically faster — often accessible within days following an online clinical assessment.
Can I get Mounjaro on the NHS if my BMI is 27?
You may be eligible if your BMI is 27–29.9 and you have at least one weight-related health condition (type 2 diabetes, hypertension, high cholesterol, sleep apnoea, or cardiovascular disease). If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply. Your GP or specialist will assess your individual case.
What happens if I stop taking Mounjaro?
Weight typically returns gradually if diet and activity habits don't change. Clinical evidence shows benefits are sustained only while continuing the medication alongside lifestyle changes. Stopping should be discussed with your prescriber, who will advise on safe discontinuation. Weight loss injections are tools to support sustainable habit change, not permanent solutions.
Does the NHS prescribe Mounjaro as a KwikPen?
Yes, Mounjaro is supplied as a pre-filled KwikPen device containing four weekly injections. Both NHS and private routes use the same KwikPen delivery system. You'll store unopened pens in the fridge at 2–8°C, and rotate injection sites weekly between your abdomen, thigh, or upper arm.
Ready to take control of your weight loss journey?
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