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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How to Use Mounjaro Pen: UK Access & Cost Guide
The Mounjaro KwikPen is a once-weekly injectable medication for weight management available in the UK. This guide explains how to use the device, what it costs, and the two main routes to access tirzepatide in the UK—through specialist NHS services or private online prescription. Understanding both the practical injection steps and the real costs involved helps you make an informed decision about whether Mounjaro is right for you.
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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.
UK Private Prescription Costs & Access Routes
Accessing Mounjaro in the UK involves two distinct pathways, each with different costs and waiting times. Through the NHS route, tirzepatide is available via specialist tier 3 weight management services following referral from your GP. However, NHS availability varies significantly by region—some areas have extensive waiting lists stretching many months, while others may not currently fund the medication. Through the private route, you can access a prescription following an online consultation with a UK-licensed prescriber. Private costs typically range from £129 to £320 per month depending on the dose and provider, with each KwikPen containing four weekly doses. The 2.5 mg starting dose is usually less expensive than higher maintenance doses (5 mg to 15 mg). Many people choose the private route to avoid NHS waiting lists, though some use NHS services where available and faster. Your GP can advise whether you meet NHS eligibility criteria for specialist referral, or you can proceed directly to private prescription assessment without NHS involvement.
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.
Using the Mounjaro KwikPen: Injection Steps & NHS Support
The Mounjaro KwikPen is straightforward to use once you've received training. Remove the pen from the refrigerator 15–30 minutes before injection to allow it to warm to room temperature. Choose your injection site—stomach (abdomen), upper thigh, or upper arm—and clean the area with an alcohol wipe. Hold the pen perpendicular to skin, press the button firmly, and hold for 3 seconds. The needle retracts automatically after injection. Rotate your injection site each week to reduce irritation. On the NHS, your prescriber will provide detailed training before your first dose. Privately, many providers offer injection training videos or guidance with your first prescription. Both routes supply patient information leaflets with complete instructions. Store unopened pens in the fridge at 2–8°C; after first use, you can keep the pen at room temperature for up to 30 days before disposal.
- 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 on private prescription in the UK?
Private Mounjaro costs typically range from £129 to £320 per month depending on your dose and provider. Starting doses (2.5–5 mg) are generally cheaper than higher maintenance doses. Each KwikPen contains four weekly injections. Prices vary between GPhC-registered providers, so it's worth comparing quotes.
Can I get Mounjaro free on the NHS in the UK?
Yes, but access is limited. NICE has approved tirzepatide for NHS use within specialist tier 3 weight management services. You need a GP referral and must meet strict eligibility criteria. Availability and waiting times vary dramatically by region—some areas have significant waiting lists, others don't currently fund it.
What happens during a private Mounjaro consultation?
A UK-licensed prescriber will assess your medical history, weight, BMI, and any health conditions via an online consultation. They'll check your eligibility, discuss side effects, and confirm you understand how to use the KwikPen. If approved, your prescription is sent to a GPhC-registered pharmacy for delivery.
Do I need a GP referral to get Mounjaro privately?
No. Private prescription routes do not require GP referral—you access the prescription directly through an online assessment with a licensed prescriber. However, telling your GP you're using Mounjaro is recommended so they can monitor your health and adjust other medications if needed.
How often will I need to pay for Mounjaro if I'm taking it privately?
You pay monthly for your prescription. Each KwikPen lasts four weeks (one injection per week). If you're titrating up doses (increasing every 4 weeks), you'll order a new pen monthly until you reach your maintenance dose, then continue as long as you're taking the medication.
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.