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
Can Mounjaro Be Stored at Room Temperature?
Yes, Mounjaro (tirzepatide) can be stored at room temperature for a limited time, but only after the KwikPen has been opened and used. Before first use, your Mounjaro pen must be kept refrigerated. Once you start using your pen, you can store it at room temperature (below 30°C) for up to 30 days. After that, it must be disposed of. Understanding proper Mounjaro storage is essential for maintaining the medication's effectiveness and safety whilst using this prescription-only injection for weight management in the UK.
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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 Rules — Before and After First Use
Before opening: Unopened Mounjaro KwikPen devices must be stored in a refrigerator at 2°C to 8°C. Keep the pen in its original carton to protect it from light. Do not freeze — if your pen has been frozen, do not use it. Unopened pens can be used until the expiry date printed on the carton as long as they remain refrigerated.
After first use: Once you've injected your first dose, you can remove the pen from the fridge. It can then be stored at room temperature (below 30°C) for up to 30 days. This makes Mounjaro practical for travel and daily use — you don't need to keep it cold once started.
Disposal: Whether stored in the fridge or at room temperature, you must dispose of your Mounjaro KwikPen exactly 30 days after first use, even if there are still doses remaining inside. Do not use it beyond this point.
- Never leave your pen in direct sunlight or near heat sources
- Never store in a car on a hot day
- Check the appearance — do not use if the liquid looks cloudy or discoloured
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.
NHS Prescribing and Storage Responsibility
When you receive your Mounjaro prescription through NHS specialist services or via a private online prescriber in the UK, your pharmacist or prescriber should provide clear storage instructions. If you're unsure about storage, contact your pharmacist or GP for guidance — they can confirm the current temperature and expiry status of your specific pen.
Proper storage protects both your health and ensures your medication works effectively. If your Mounjaro has been exposed to freezing temperatures, heat, or direct sunlight, do not use it. Request a replacement from your prescriber or pharmacy. Use our free GLP-1 weight loss calculator to understand your estimated results when taking Mounjaro — consistent, safe use of your medication will support your weight management goals alongside diet and exercise changes.
- 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 travel with Mounjaro at room temperature?
Yes. Once your KwikPen is opened, you can carry it in a bag or pocket at room temperature (below 30°C) for up to 30 days. For longer trips, consider a small insulated travel case. Never leave it in direct sunlight or in a hot car. Always keep it away from extreme heat.
What temperature is too hot for Mounjaro storage?
Mounjaro should not be stored above 30°C. If your room exceeds this temperature regularly, keep the pen in a cool cupboard or drawer. In summer or warm climates, an air-conditioned room is ideal. High temperatures can damage the medication and reduce its effectiveness.
How long can Mounjaro stay out of the fridge after opening?
Exactly 30 days. After your first injection, your KwikPen can be kept at room temperature for up to 30 days. After 30 days, dispose of the pen safely, even if doses remain. Do not use it beyond this timeframe — the medication's stability cannot be assured after 30 days.
What happens if my unopened Mounjaro freezes?
Do not use it. If your unopened KwikPen has been frozen, it must be disposed of and replaced. Freezing damages the tirzepatide solution. Always store unopened pens in a standard fridge at 2–8°C, never in the freezer compartment.
Should I refrigerate Mounjaro once I start using it?
No. Once you've injected your first dose from the KwikPen, you can keep it at room temperature. You do not need to return it to the fridge between injections. Room temperature storage (below 30°C) is safe and convenient for the full 30 days after opening.
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.