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 Temperature Should Mounjaro Be Stored At?
Mounjaro (tirzepatide) must be stored at specific temperatures to remain safe and effective. Unopened Mounjaro KwikPen devices should be kept in a refrigerator between 2°C and 8°C, protected from light in their original carton. Once you start using a pen, you can keep it at room temperature below 30°C for up to 30 days. Never freeze Mounjaro — if it freezes, the medication becomes unsafe and must be disposed of. Proper storage is essential to maintain the medicine's effectiveness throughout your treatment course.
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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 Storage Requirements — Detailed Guidance
Unopened Mounjaro KwikPen storage: Keep all unused pens in a refrigerator at 2°C to 8°C (standard fridge temperature). Store in the original carton to protect from light exposure. Mounjaro can remain in the refrigerator until the expiry date printed on the carton if kept at this temperature consistently.
After first use: Once you inject your first dose from a pen, you can store that pen at room temperature below 30°C for up to 30 days. Keep away from direct sunlight and heat sources. After 30 days from first use, dispose of the pen safely — even if insulin remains.
What to avoid: Never freeze Mounjaro. Do not store above 30°C. Do not leave in direct sunlight. Do not use a pen that has been frozen, even if it thaws.
Proper storage of your tirzepatide prescription ensures each dose delivers the intended benefit. Check the temperature of your fridge if possible — many UK household fridges sit at 4–5°C, which is ideal.
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.
Travel and Storage Tips for Mounjaro Users
If you're travelling within the UK or abroad, bring an insulated cool bag or portable fridge pack to maintain temperatures between 2–8°C during transit. Do not leave Mounjaro in a hot car or direct sunlight, even briefly. When travelling on long flights, keep unopened pens in your hand luggage in a cool bag rather than checked baggage, where temperatures may drop below freezing in cargo holds.
If you're unsure whether your Mounjaro has been stored correctly — for example, if it's been left at room temperature for longer than 30 days or exposed to heat — do not use it. Contact your pharmacy or prescriber for guidance on safe disposal and a replacement prescription. Your GP or licensed prescriber can discuss your specific storage needs when you receive your NHS NICE-approved or private Mounjaro UK prescription.
- 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 store Mounjaro in the freezer?
No. Freezing damages tirzepatide and makes it unsafe to use. If Mounjaro freezes, even partially, discard it. Always maintain temperatures between 2–8°C in a standard refrigerator, never a freezer.
How long can Mounjaro stay out of the fridge after I start using it?
Once you inject your first dose, you can keep that pen at room temperature below 30°C for up to 30 days. After 30 days, dispose of the pen safely, even if medication remains in it.
What's the difference between storing unopened and opened Mounjaro?
Unopened pens must stay at 2–8°C in the fridge. Opened pens can be kept below 30°C for 30 days. This difference reflects how the medication's stability changes once you start using it.
Can I take Mounjaro on holiday?
Yes. Use an insulated cool bag to keep unopened pens at 2–8°C during travel. Once opened, you can store at room temperature below 30°C for 30 days, making short holidays manageable without special equipment.
What should I do if I'm not sure if my Mounjaro has been stored correctly?
If your pen has been left above 30°C, frozen, or in sunlight longer than expected, do not use it. Contact your pharmacy or prescriber immediately. They can advise on safe disposal and issue a replacement prescription if needed.
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.