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
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How to Store Mounjaro Safely — Complete UK Guide
If you've been prescribed Mounjaro (tirzepatide), proper storage is essential to keep your medication safe and effective. This guide explains exactly how to store your Mounjaro KwikPen before and after first use, whether unopened pens need refrigeration, what to do if your pen freezes, and how to dispose of used pens correctly. Understanding storage requirements helps ensure your prescription medication works as intended and remains safe to use 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 Before and After First Use
Unopened Mounjaro pens must be stored in a refrigerator at 2°C to 8°C. Keep pens in their original carton to protect them from light. Unopened pens can be used until their expiry date if stored correctly in the fridge. Never freeze Mounjaro — if a pen has been frozen, do not use it and contact your pharmacist for advice on replacement.
- Store unopened pens at 2–8°C in a standard household fridge
- Keep pens in the original carton — do not store loose pens
- Place pens in the fridge door or main compartment, away from the freezer
- Check the expiry date on the carton before use
After first use, Mounjaro can be stored at room temperature (below 30°C) for up to 30 days. Once you've started using a pen, you have 30 days to complete that pen before you must dispose of it, even if there is still medication inside. This applies whether you store it in the fridge or at room temperature — the 30-day clock starts when you first inject from that pen.
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 vs Private Access and Cost Considerations
Mounjaro is available through NHS specialist tier 3 weight management services and through private prescription routes in the UK. NHS access requires referral to a specialist service, but availability and waiting times vary significantly by region. Private access through a UK-licensed prescriber and GPhC-registered pharmacy is available without NHS referral, though costs vary by dose and provider.
Mounjaro eligibility requires either a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, hypertension, or sleep apnoea. You can check your personal BMI using our free BMI calculator above. Whether you access Mounjaro through NHS or private routes, storage requirements remain identical — all pens must be kept at 2–8°C until opened, then used within 30 days after first use.
- 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 door of my fridge?
Yes, the fridge door is a suitable storage location for unopened Mounjaro pens, as long as the temperature remains at 2–8°C. Keep pens in their original carton. Avoid storing near the freezer compartment where temperatures may dip below freezing. Check your fridge thermometer to confirm the correct temperature range.
What happens if my Mounjaro pen freezes?
If your Mounjaro pen has been frozen, do not use it. Freezing damages the medication and makes it unsafe to inject. Contact your pharmacist or prescriber immediately — they can arrange a replacement pen. Always keep Mounjaro away from the freezer compartment or ice trays.
How long can I keep Mounjaro at room temperature after opening?
Once you've injected from your Mounjaro pen for the first time, you have exactly 30 days to use that pen, whether you store it in the fridge or at room temperature (below 30°C). After 30 days, dispose of the pen even if medication remains. The 30-day timer starts from your first injection, not from the date of purchase.
Can I travel with Mounjaro on holiday?
Yes, you can travel with Mounjaro. In the UK and EU, you can carry it in carry-on or checked baggage. Before international travel outside the EU, check entry requirements with your destination country's customs or health authority. Keep pens in their original carton. For flights, unopened pens should be refrigerated; once opened, store at room temperature (below 30°C) within the 30-day window.
How do I dispose of my used Mounjaro pen?
Never put Mounjaro pens in regular household waste or recycling. Take used pens to your local pharmacy or GP surgery — they have needle disposal units and will dispose of your pen safely and confidentially. Most pharmacies accept used pens at no cost. Ask your pharmacist where the needle disposal point is located.
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.