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 Mounjaro — UK Temperature & Safety Guide
Proper storage of your Mounjaro KwikPen is essential for the medication to work effectively and remain safe. This guide explains exactly how to store tirzepatide in the UK, including temperature requirements before and after opening your pen, how long you can keep it at room temperature, and what to do if your medication has been exposed to freezing temperatures. Whether you've just started Mounjaro or you're progressing through dose titration, correct storage protects your investment and ensures consistent results.
10,000+ calculations today · NHS-aligned thresholds · 100% free
Calculate Your BMI Instantly
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 Storage Temperature Requirements
Unopened Mounjaro KwikPens must be stored in a refrigerator at 2°C to 8°C — this is your standard fridge temperature. Keep pens in their original carton to protect them from light exposure. Unopened pens can be used until their expiry date as long as they remain refrigerated. Never freeze your Mounjaro — if a pen has been frozen, do not use it and contact your prescriber or pharmacy for guidance.
After opening your pen (once you've taken your first injection), you have two storage options: keep it in the fridge at 2–8°C, or store it at room temperature below 30°C. Once opened at room temperature, Mounjaro can be kept for up to 30 days before it must be disposed of. If stored in the fridge after opening, you can continue using it until the 30-day mark from first use.
- Unopened: refrigerate at 2–8°C in original carton
- After first use: fridge or room temperature (below 30°C) for maximum 30 days
- Never freeze — discard if frozen
- Keep away from heat and 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 & Travel Tips for UK Users
If you're travelling within the UK or abroad, keep your Mounjaro in a cool bag or insulated pouch with ice packs to maintain the 2–8°C range. Once you reach your destination, return it to a fridge immediately. Mark your calendar or phone with the 30-day disposal date from the day you first use your pen — this prevents accidentally using expired medication. If you're unsure whether your Mounjaro has been stored correctly, err on the side of caution and contact your prescriber or pharmacy. Before starting Mounjaro or adjusting your dose during the titration schedule, use our free BMI calculator to track how your weight changes over time and monitor your progress alongside your medication storage routine.
- 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.
What temperature should I store unopened Mounjaro at?
Unopened Mounjaro KwikPens must be stored in a refrigerator at 2°C to 8°C — the temperature of a standard UK fridge. Keep pens in the original carton to protect from light. Do not freeze.
Can I store Mounjaro at room temperature after opening it?
Yes. After your first injection, you can store your opened Mounjaro KwikPen at room temperature below 30°C for up to 30 days, or continue refrigerating it. Choose whichever is most convenient for you.
What happens if my Mounjaro gets frozen?
Do not use frozen Mounjaro. Freezing damages the medication. If your pen has been frozen, contact your prescriber or pharmacy for guidance on replacing it.
How long can I keep an opened Mounjaro pen?
You have 30 days from the date of first use to use your opened Mounjaro pen, whether stored in the fridge or at room temperature. After 30 days, dispose of the pen safely.
Can I take Mounjaro with me when travelling in the UK?
Yes. Use an insulated cool bag with ice packs to keep it at 2–8°C while travelling. Return it to a fridge at your destination. Never leave it in a hot car or direct sunlight.
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.