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 Mounjaro Kwikpen? A UK Guide
Mounjaro Kwikpen is the delivery device for tirzepatide, a prescription-only weight management injection licensed in the UK. It's a pre-filled pen that delivers a once-weekly dose. The Kwikpen comes ready to use with 4 doses per pen (4 weeks of treatment). Understanding how to store, handle, and use your Mounjaro Kwikpen properly is essential for safe and effective treatment. This guide covers everything UK patients need to know about the device itself.
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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 Mounjaro Kwikpen Works and Doses
The Mounjaro Kwikpen is a pre-filled, dial-up injection device. Each pen contains exactly 4 weekly doses and is designed for ease of use at home. The pen starts at 2.5 mg and escalates through doses: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and up to 15 mg maximum.
- Starting dose: 2.5 mg for weeks 1–4
- Escalation: Minimum 4 weeks on each dose before increasing (guided by your prescriber)
- Maximum dose: 15 mg once weekly
- Injection frequency: Once per week, on the same day each week
Your prescriber will guide your dose titration based on tolerance and clinical response. Unlike Wegovy (semaglutide), which has a gentler dose escalation, Mounjaro uses a step-up protocol. Each Kwikpen lasts exactly 4 weeks.
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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.
Storage and Handling Your Mounjaro Kwikpen
Before first use: Store unopened Kwikpens in the refrigerator at 2–8°C. Do not freeze — if frozen, discard. Keep in the original carton to protect from light until ready to use. Check the expiry date on the pen.
After first injection: You can store your pen at room temperature (below 30°C) for up to 30 days. After 30 days, dispose of the pen safely, even if medication remains. Never leave pens in direct sunlight or in hot environments like cars. If you're travelling, use an insulated cool bag with ice packs for short journeys.
- 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 do I inject Mounjaro from the Kwikpen?
Wash your hands, select your injection site (stomach, upper thigh, or upper arm), pinch the skin, insert the needle at 90 degrees, press the plunger button fully for 3 seconds, then release. The pen has an audible or tactile click to confirm completion. Refer to your patient information leaflet for detailed instructions, or ask your prescriber or pharmacist to demonstrate first.
Can I share a Mounjaro Kwikpen with someone else?
No. Each Kwikpen is prescribed to one person only. Sharing injections risks infection and is unsafe. Each patient requires their own prescription and their own device. Never share your pen with family members or friends, regardless of their weight or health status.
What if I miss a weekly Mounjaro injection?
If you remember within 4 days of your missed dose, inject as soon as you remember, then continue your normal weekly schedule from that point. If more than 4 days have passed, skip that dose and inject on your next normal scheduled day. Never take a double dose. Contact your prescriber if you miss multiple doses.
How do I know when my Mounjaro Kwikpen is empty?
Each pen contains exactly 4 doses. After your fourth injection, the pen will be empty. Count your injections or mark them in your calendar. The pen may feel lighter but will not lock or give a clear "empty" signal on all models. Order your next prescription before your current pen runs out to avoid gaps in treatment.
Is Mounjaro Kwikpen available on the NHS in the UK?
NICE has approved tirzepatide for use within NHS specialist weight management services (tier 3/4). However, NHS availability varies significantly by region and waiting lists can be lengthy. Many UK patients access Mounjaro through private online prescribing following a clinical assessment. Your GP can discuss both NHS and private options with you.
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.