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
What Is a Kwik Pen for Semaglutide?
The Kwik Pen is the pre-filled injection device used to deliver Wegovy (semaglutide) in the UK. It's a simple, self-administered pen that contains four weekly doses of semaglutide at your prescribed strength. Each Kwik Pen is designed to be user-friendly, with a dial mechanism to select your dose and an easy-to-use needle system. If you're considering Wegovy as part of your NHS health guidance or private weight management plan, understanding how the Kwik Pen works is essential for safe and effective use. This UK health information covers everything you need to know about this delivery device.
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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.
How the Kwik Pen Works
The Kwik Pen is a pre-filled injection pen containing four doses of semaglutide, the active ingredient in Wegovy. Each pen delivers a once-weekly injection at your prescribed dose, which your prescriber will determine during your clinical assessment.
How to use it:
- Remove the pen from the fridge 15–30 minutes before injection to allow it to reach room temperature
- Check the solution in the viewing window — it should be clear and colourless
- Dial the dose selector to your prescribed dose amount (typically 0.25 mg, 0.5 mg, 1 mg, 1.7 mg, or 2.4 mg)
- Insert the needle into your chosen injection site (stomach, upper thigh, or upper arm)
- Press and hold the injection button until you hear a click
- Count to six slowly to ensure the full dose is delivered
- Remove the needle and dispose of it safely in a sharps bin
The Kwik Pen's dial system makes it nearly impossible to administer the wrong dose, as it only allows selection of your scheduled dose amount.
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.
Storage and Safety
Before first use: Store unopened Kwik Pens in a refrigerator at 2°C to 8°C. Do not freeze them — if a pen is frozen, it cannot be used. Keep pens in their original carton away from direct light and heat. Unopened pens can be used until the expiry date printed on the box.
After first use: Once you've used your first dose from a Kwik Pen, you can store it at room temperature (below 30°C) for up to 30 days. After 30 days, dispose of the pen safely, even if it contains remaining doses. Never share your pen with another person, as it is single-use only. Always keep the needle cap on between injections to prevent contamination and needle damage.
- 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.
Can I use the Kwik Pen if I've never given myself an injection before?
Yes. The Kwik Pen is specifically designed for self-administration by people with no injection experience. Your prescriber or pharmacist will provide clear instructions, and most people find it straightforward after the first use. Many people report that the needle is very fine and the injection is relatively painless compared to other injectable medications.
What if I miss a dose or forget to use my Kwik Pen on the scheduled day?
If you miss your weekly injection within 4 days of the scheduled day, take it as soon as you remember and continue your normal weekly schedule from there. If more than 4 days have passed, skip that dose and take your next injection on your usual scheduled day. Never take two doses within 3 days to catch up.
Where should I inject the Kwik Pen?
The Kwik Pen can be injected into three areas: your stomach (abdomen), the front of your upper thigh, or your upper arm (though the arm requires assistance). Rotate your injection site each week to prevent irritation or lipohypertrophy (fatty lumps under the skin).
How do I dispose of a used Kwik Pen safely?
Place your used pen in a sharps bin (a yellow sharps container available from pharmacies or your GP surgery). Never put it in regular household waste or recycling. Once a sharps bin is full, contact your local council or pharmacy for safe disposal instructions. Some pharmacies may also accept used pens directly.
Can the Kwik Pen be used alongside other weight loss support?
Yes. Wegovy delivered via Kwik Pen works best when combined with a reduced-calorie diet and increased physical activity. Many people track their progress alongside lifestyle changes using tools like the MyWeightCheck weight converter and progress tracker to monitor both their weight loss journey and healthy weight targets.
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.