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
How to Store Your Mounjaro Pen — UK Guidelines
Storing your Mounjaro pen correctly is essential for keeping the medication safe and effective. Whether your Mounjaro KwikPen is unopened or you've already started using it, UK prescribing guidance and the product information leaflet provide clear storage instructions. Proper storage protects the tirzepatide from damage and ensures each weekly injection works as intended. This guide covers refrigeration, room temperature storage, and what to do when you've finished your treatment.
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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.
Unopened and In-Use Storage Requirements
Unopened Mounjaro pens must be stored in a refrigerator at 2°C to 8°C. Keep them in their original carton to protect from light. Unopened pens can be used until the expiry date printed on the packaging if stored correctly in the fridge. Do not freeze your pens — if a pen freezes, discard it and do not use it.
Once you've used your first Mounjaro dose, the pen can be stored at room temperature below 30°C for up to 30 days. You must dispose of the pen after 30 days, even if there is medication remaining. This 30-day room temperature window is useful if you're travelling or don't have reliable fridge access, but keep the pen away from heat, direct sunlight, and radiators.
- Unopened: fridge (2–8°C) until expiry date
- After first use: room temperature (below 30°C) for maximum 30 days only
- Never freeze Mounjaro
- Never expose to heat or direct sunlight
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.
Practical Storage Tips and Disposal
When storing your Mounjaro KwikPen at home, keep it in a cool, dark place away from children and pets. If you use the GLP-1 weight loss calculator to project your weight loss journey, you may be using Mounjaro for several months — plan your storage accordingly. Write the "use by" date on your calendar after your first injection so you know when to dispose of the pen.
When a pen is empty or the 30-day room temperature period has passed, place it in your household sharps bin or take it to a pharmacy for safe disposal. Never throw Mounjaro pens in regular household waste. If you have questions about storage or disposal, your prescriber or pharmacist can provide NHS guidance specific to your situation.
- 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 keep my Mounjaro pen in the fridge door?
Yes, the fridge door is acceptable as long as the temperature stays between 2–8°C. However, the back of the fridge shelf is often more stable. Avoid the door if your fridge temperature fluctuates, and never place Mounjaro near the freezer compartment where it might freeze.
What if my Mounjaro pen freezes?
If your Mounjaro pen freezes, do not use it. Discard it safely in a sharps bin or take it to a pharmacy. Contact your prescriber to arrange a replacement pen, as frozen tirzepatide is not safe to inject.
How long can I keep an unopened Mounjaro pen?
Unopened pens can be stored in the fridge until the expiry date on the packaging. This is typically around 2–3 years from manufacture. Always check the expiry date before using.
Can I travel with my Mounjaro pen?
Yes. You can carry an unopened pen in a cool bag with ice packs when travelling. Once you've started using it, you have 30 days at room temperature, which covers most holidays. Plan ahead if travelling to very hot climates.
What should I do with an empty Mounjaro pen?
Place empty pens in a household sharps bin. If you don't have a sharps bin, take the pen to your local pharmacy — they will dispose of it safely and legally. Never put Mounjaro pens in regular rubbish.
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.