How to Store Mounjaro to Keep it Safe and Effective

If you’ve been prescribed Mounjaro (tirzepatide), you’ll need to store it correctly when it arrives.

Without proper storage, Mounjaro may lose its effectiveness. Using a pen damaged by heat or freezing could also increase the chance of unpleasant side effects.

As well as following correct Mounjaro dosage, storing it the right way will make sure your pen is safe and effective. So, this article will guide you through how to store Mounjaro before first use and after first use. We also explain when to discard your pen and how to store it when travelling.

How to Store Your Mounjaro Pen Before First Use

Before you open your Mounjaro KwikPen for the first time, it must be stored in the correct conditions. The manufacturer advises you to keep unopened Mounjaro pens refrigerated between 2°C to 8°C.

“This will ensure that you’re maximising the shelf life of the product if it’s not going to be used immediately,” explains Aamina Rafiq, Simple Online Pharmacy’s superintendent pharmacist.

If you forget to keep your mounjaro in the fridge it will only last 30 days as if you had opened it.

Keep it in the original box to protect it from light and any bumps in the fridge.

Before your first injection, check the expiration date. Make sure the liquid inside looks clear. The liquid should not be cloudy or discoloured and it should be free of particles.

Do not freeze Mounjaro. If your pen is frozen, do not use it.

How Long Does Mounjaro Last in the Fridge?

If you keep them in the fridge (between 2°C and 8°C), unopened Mounjaro pens are safe to use until their expiry date. The expiry date is printed on the pen’s label.

How to Store Mounjaro After First Use

Once you have used your Mounjaro pen for the first injection, it has an expiry date of 30 days. You can keep the pen in the fridge between 2°C and 8°C. Alternatively, you can store it at room temperature (below 30°C).

After it has been open for 30 days, you should throw it away even if there is still some medicine left inside.

Each pen comes pre-filled with a one-month supply of treatment (four doses, which you inject each week). Doses remaining after 30 days from first use should not be used. This means that, if you’ve missed a dose, it might not be safe to use all four doses.

Once you’ve finished injecting each dose, take a moment to remove the needle. This helps prevent air from getting into the pen and keeps each dose accurate.

Why the Correct Mounjaro Storage Temperature Is So Important

Temperature is important when storing Mounjaro. The medicine inside, tirzepatide, is made from proteins called peptides. These can break down if they get too cold or too warm, which means the medicine may not work as well.

That’s why you must keep unopened pens in the fridge between 2°C and 8°C and, once open, below 30°C for up to 30 days.

Again, never freeze Mounjaro. Freezing damages the pen and you should hand it into your local pharmacy for disposal if it has been frozen. If you store it in the fridge, choose a stable spot. The back of the fridge can sometimes be too cold or near the freezer zone, the pen might freeze or suffer cold damage.

When to Discard Your Pen

Using a pen for too long, or one that hasn’t been stored properly, can make the medicine less effective or unsafe.

You should discard your pen if any of the following apply:

• It Has Reached its Expiry Date (Check the Label): Each pen and box has an expiry date printed on it. Once that date passes, the medicine may no longer work properly, even if it looks fine.
• It’s Been Open for 30 Days: Once you start using the pen, a countdown begins. After 30 days, the medicine may begin to break down. Even if there is still some left, it is safer to throw it away and start a new one.
• It Has Been Frozen or Exposed to Heat Above 30°C: Tirzepatide is sensitive to temperature changes. If you’ve left the pen in a hot car, near a radiator or it’s frozen, it may no longer be stable. So you shouldn’t use it.
• The Liquid Looks Cloudy, Discoloured or Has Bits in It: The medicine inside should be clear or slightly yellow. If it looks cloudy, discoloured or has particles floating inside, the pen could be damaged or contaminated. It’s best to dispose of it safely and use a new one.

Always use a sharps container or another approved disposal method for used injection pens. Never throw them in the household bin where they could injure someone. Pharmacies can often provide sharps bins or take used pens back for safe disposal.

If you are unsure whether your pen is still safe to use, ask your pharmacist or healthcare provider before injecting. It’s always better to check than risk using a pen that may not work as it should.

How to Store Mounjaro When Travelling

Travelling doesn’t have to disrupt your weight loss journey. You can still use Mounjaro when on the move; it just requires a bit of planning.

Here’s how you can make sure the pens stay at the right temperature:

• Use a Cool Bag: If you won’t have access to a fridge straight away, use an insulated cool bag with gel packs to keep the pen cool. Don’t let the ice packs touch the pen directly, as that could freeze it.
• Keep the Medication in its Original Packaging: It protects the pen from light. It also makes it easier to show at airport security or customs if needed.

To minimise disruption when travelling abroad:

• Keep Your Pen in Hand Luggage: Whenever you can, keep your pen in your hand luggage rather than in a suitcase that goes in the plane’s hold. This way, you can keep an eye on it and make sure it doesn’t get too hot or too cold.
• Check the Rules: Before you travel, check the rules for carrying injectable medicines in the country you’re visiting. Bring your prescription or a letter from your GP explaining what the medicine is for, just in case someone asks you.

Key Takeaways

• Store Unopened Mounjaro Pens in the Fridge: Keep them between 2°C and 8°C until you’re ready to use them. This helps the medicine stay stable and work as it should when you inject it.
• After First Use, Keep it at Room Temperature: You can keep your pen stored unrefrigerated (below 30°C) for up to 30 days. Just make sure it stays out of direct sunlight and away from heat sources.
• Never Freeze the Pen: Freezing can damage the medicine inside, making it less effective. If your pen has ever been frozen, it’s best to throw it away and start with a new one.
• Discard at Expiry or After 30 Days: Once your pen has expired or has been open for 30 days, throw it away. You’ll need to discard it even if there’s some medicine left.
• Travelling? Plan Ahead: Keep your pen in your hand luggage. Use an insulated cool bag with gel packs and avoid letting it get warmer than 30°C. Check travel rules in advance so there are no problems carrying your medicine.
• When in Doubt, Talk to Your Doctor or Pharmacist: If you think your pen has been stored incorrectly, ask for advice before using it. It’s always safer to replace the pen than risk using one that may not work properly.

FAQs

Do You Have to Keep Mounjaro in the Fridge?

You have to keep your Mounjaro pen in the fridge before you open it, keeping it at a temperature between 2°C and 8°C. However, after the first use you can keep it at room temperature for up to 30 days.

How Long Can Mounjaro Be Out of the Fridge?

You can keep Mounjaro out of the fridge for 30 days. After that, it’s not safe to use, so you’ll need to dispose of it safely.

Where to Dispose of Mounjaro Pens?

Dispose of any used needles in a sharps bin. Under the Environmental Protection Act 1990, it’s illegal to dispose of sharps in general household waste. You can order a sharps bin from most providers.

Clinical waste collection is decided at a local council level. So you’ll have to check with your local council whether they have a collection service for sharps bins. You may have to pay a fee. Your local pharmacy or GP practice may also be able to dispose of used needles for you.

After you’ve removed the needle, you can throw away your used pens in your household waste bin.

References

Eli Lilly and Company, 2023. MOUNJARO® (tirzepatide) Injection – Instructions for Use (US) [PDF online]. Available from: https://pi.lilly.com/us/mounjaro-us-ifu.pdf (Accessed: 22 September 2025). 

Eli Lilly and Company, 2025. What should I do if I accidentally froze the MOUNJARO® KwikPen®? [online]. Available from: https://www.lilly.com/en-CA/resources/faq/mounjaro-kwikpen/accidentally-frozen-mounjaro (Accessed: 22 September 2025).

Eli Lilly UK, 2025. How should the Mounjaro (tirzepatide) KwikPen be stored? [online]. Available from: https://medical.lilly.com/uk/products/answers/how-should-the-mounjaro-tirzepatide-kwikpen-be-stored-217607 (Accessed: 22 September 2025).