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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Your First Day on Mounjaro — Cost and Access in the UK
Starting Mounjaro (tirzepatide) marks an important step in your weight management journey, but understanding how to access it and what it costs is essential. In the UK, you can obtain Mounjaro through either NHS specialist services or private prescription routes, with costs varying significantly depending on which path you choose. This guide explains both options, what happens on your first day, and how to get started.
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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.
Mounjaro UK Cost and Access Routes
NHS access: Mounjaro is now approved by NICE for use within NHS specialist weight management services. However, NHS access is limited to tier 3 and tier 4 specialist weight management centres — you cannot obtain it through a standard GP prescription. You'll need a referral from your GP to a specialist service in your region. Availability varies significantly by region (Integrated Care Board), and waiting lists can be several months in some areas.
Private prescription cost: Through private UK-licensed online prescribers, Mounjaro typically costs between £129 and £320 per month depending on your dose. The starting dose (2.5 mg) is usually at the lower end, with costs increasing as you titrate through higher doses (5 mg, 7.5 mg, 10 mg, 12.5 mg, 15 mg). Each KwikPen contains 4 weeks of injections. Private prescribing requires an online clinical assessment but does not require NHS referral.
- NHS route: Free if eligible through specialist services
- Private route: £129–£320/month depending on dose
- Both require a prescription from a UK-licensed prescriber
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.
What Happens on Your First Day — NHS vs Private
If accessing through the NHS, your first day will involve attending your specialist weight management service clinic for an initial consultation, baseline health checks, and prescription. If using private online prescribing, your first day involves completing an online health assessment with a UK-licensed prescriber, who will review your eligibility and medical history. Once approved, your prescription is sent to a GPhC-registered pharmacy and your first Mounjaro KwikPen is dispensed. Your first injection will be the 2.5 mg starting dose — administered either at the clinic (NHS) or at home (private). You'll be shown how to use the KwikPen device, and told when to expect your second injection four weeks later. Use our GLP-1 weight loss calculator to understand what dose progression might look like over your treatment journey.
- 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.
How much does Mounjaro cost in the UK privately?
Private Mounjaro costs typically range from £129 to £320 per month depending on your dose. Starting doses (2.5 mg) are usually around £129–£150, escalating to £250–£320 for maintenance doses (10–15 mg). Each pen covers 4 weeks. Costs vary slightly between providers but are generally comparable across GPhC-registered pharmacies.
Can I get Mounjaro free on the NHS in the UK?
Yes, if you meet the criteria and are referred to a specialist tier 3 weight management service. However, NHS access is limited and not available through standard GP prescription. Your GP must refer you to your local specialist service, which may have a waiting list of several months. Ask your GP about tier 3 services in your area.
What's the difference between NHS and private Mounjaro access?
NHS access is free but limited to specialist services with potential waiting lists and regional variation. Private access is faster (usually within days), doesn't require NHS referral, but costs £129–£320/month. Both require clinical assessment and a UK prescription from a licensed prescriber.
How long does private online Mounjaro prescription take?
Most private online assessments are completed within 24–48 hours. Once approved, your prescription goes to a GPhC-registered pharmacy, and your first KwikPen is typically dispatched within 1–3 working days. You can start your first injection immediately upon receipt.
What should I do before my first Mounjaro injection?
Ensure you've had a clinical assessment (NHS or private). Read the instructions included with your KwikPen. Check the injection sites (stomach, thigh, or upper arm — rotate weekly). Make sure you have any prescribed support materials. Track your starting weight using our free progress tracker to monitor your journey from day one.
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.