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 Inject Mounjaro with the Kwikpen Device
Mounjaro (tirzepatide) comes in a pre-filled Kwikpen device that makes self-injection straightforward at home each week. This guide covers the step-by-step injection process, UK prescription costs, and how to access Mounjaro through both NHS specialist services and private online prescribing. Whether you're considering this weight management medication or already prescribed it, understanding the practical and financial aspects helps you make informed decisions.
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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 Kwikpen Injection Steps & UK Access Routes
How to inject Mounjaro using the Kwikpen:
- Remove the pen from the refrigerator 15 minutes before injection — allow it to reach room temperature
- Check the liquid is clear and colourless; do not use if cloudy or discoloured
- Select your injection site (stomach, thigh, or upper arm) and rotate each week to avoid lipohypertrophy
- Pinch the skin, insert the needle at a 90-degree angle, and hold the pen in place for 6 seconds
- Release the skin and remove the needle carefully
- Store used pens at room temperature (below 30°C) for up to 30 days, or return to the fridge if unopened
In the UK, you can access Mounjaro through two main routes. NHS route: Referral to a tier 3 specialist weight management service via your GP — availability and waiting times vary significantly by region and ICB. Private route: Online consultation with a UK-licensed prescriber followed by dispensing from a GPhC-registered pharmacy — typically faster than NHS access. Both routes require clinical assessment to confirm eligibility based on BMI and health conditions.
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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.
Mounjaro UK Prescription Cost & What to Expect
Private Mounjaro costs in the UK typically range from £120–£300 per month depending on the dose you're on — starting doses (2.5–5 mg) are cheaper, while maintenance doses (10–15 mg) cost more. This usually includes the online consultation, prescription, and monthly supply of four pens. NHS route: If prescribed through specialist services, Mounjaro is available on the NHS, though regional variation in availability remains significant. When you receive your prescription privately, you'll have an online assessment where a UK-licensed prescriber reviews your weight, BMI, medical history, and any medications before deciding if Mounjaro is appropriate for you. Use our free GLP-1 weight loss calculator to estimate potential weight loss at different doses, and our BMI calculator to check your current BMI category — both tools help you prepare for your consultation.
- 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 long does a Mounjaro Kwikpen injection take?
The actual injection takes around 6 seconds. Including preparation time (checking the pen, preparing your skin, and selecting a site), the whole process typically takes 2–3 minutes. Most people find it becomes quicker and easier with practice.
Can I inject Mounjaro at the same time each week, or does it need to be exact?
You should inject once weekly, preferably on the same day each week for consistency. If you're a day or two off schedule, that's generally fine — but if you miss your dose by more than 4 days, skip that dose and take your next one on your normal scheduled day. Never take a double dose.
What's the difference between NHS and private Mounjaro prescriptions in the UK?
NHS Mounjaro is free at point of care but requires a GP referral to specialist services with potential waiting lists of many months. Private Mounjaro requires an online consultation (typically £20–£50) and costs £120–£300 per month depending on dose, but is available more quickly without NHS waiting lists.
Is there a cheaper way to access Mounjaro in the UK?
If you're eligible for NHS specialist weight management services, Mounjaro prescribed through the NHS is free. Otherwise, private prescribing is the most straightforward route — costs vary between providers, so comparing prices across GPhC-registered pharmacies can help you find the best value.
What injection sites should I use for Mounjaro Kwikpen?
Use your stomach (most common), upper thigh, or upper arm. Always rotate your site each week to prevent lipohypertrophy (thickening of fatty tissue). Never inject into the same spot twice in a row, and avoid areas with bruising or irritation.
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.