How Long Is Mounjaro Good Out of the Refrigerator? (October 2026)

01 · The core answer

How long can Mounjaro be out of the fridge?

An in-use Mounjaro KwikPen can be kept out of the fridge, not above 30°C, for up to 30 days. After that it should be discarded, even if some medicine appears to be left.¹¹³

The 30 days is a ceiling, not a target. Each KwikPen contains four weekly doses.

The pen must be in use. It must stay not above 30°C. And it must be discarded after the in-use period. Miss any of the three and the 30-day figure no longer applies.

02 · Unopened pens

What about an unopened pen left out of the fridge?

Unopened pens should be kept in the fridge and keep until the expiry date printed on the box.¹ The 30-day allowance is for pens already in use, so do not stretch it to cover a sealed pen.

If an unopened pen has been out of the fridge, check with the pharmacy before using it rather than relying on a remembered day limit. Figures circulating online often come from other countries' labels.¹³

Tell us when the pen was out, roughly how warm the place was and whether it was ever near freezing. That gives the pharmacy what it needs to advise you. If you ordered from us, our team can be reached Monday to Friday by email, account chat or phone, and the prescribing team can help with storage questions as part of aftercare.

03 · Your next step

What should you do right now?

Work out which of three situations you are in, because the action differs for each.

• Pen in use, out of the fridge, within the in-use window and not above 30°C: carry on as normal and keep the cap on.
• Pen in use, past the in-use window: discard it, even if it is not empty, and speak to your prescriber about the dose timing.
• Unopened pen that has been warm, frozen or unrefrigerated for an unknown time: do not inject it. Contact the pharmacy first.

If you are still deciding whether treatment is right for you, our weight loss clinic explains the service, and the Mounjaro pen page shows current doses and prices, from £169.99 at the 2.5mg starting dose. Every pen is delivered in temperature-controlled packaging.

Related guides: How long can mounjaro stay out of refrigerator and How long can i leave mounjaro out of the refrigerator and How long can you keep mounjaro in the refrigerator and What happens if you leave mounjaro out of the fridge and How long can tirzepatide be stored in the refrigerator.

04 · Official storage rules

The official Mounjaro storage rules

Keep Mounjaro pens in a fridge at 2–8°C and never freeze them. Once in use, a pen can be kept out of the fridge not above 30°C for up to 30 days, which is useful for short trips, after which it should be discarded. Keep the pen cap on to protect it from light, and never use a pen that has been frozen.¹¹³

• Fridge at 2–8°C: this is where unopened pens live until first use.
• Never freeze: a frozen pen must not be used, however it looks once thawed.
• Below 30°C for up to 30 days once in use: this is the out-of-fridge allowance.
• Discard after that: there is no extension for a pen that still seems to have medicine inside.
• Cap on: light protection applies whether the pen is in the fridge or out of it.

05 · Fridge versus room temperature

Fridge or room temperature: which is better day to day?

For the pen you are currently using, either is acceptable within the rules: in the fridge, or out of it not above 30°C for up to 30 days.¹ Choose whichever fits your routine and makes you less likely to forget the injection.

Many people keep the in-use pen in the fridge anyway, because it is easier to track. Others keep it in a drawer at home, a desk at work or a bag during a trip. Both approaches follow the licence as long as the temperature stays not above 30°C and the pen is discarded once the in-use period ends.

The one habit worth building is noting the date you first used each pen. Write it on the box or in your phone. If you use a tracking tool such as the free GLPTrackr companion app, you can log injection dates there too. A written start date removes the guesswork when you later wonder whether you are inside the window.

06 · Why the 30-day limit exists

Why can't you use Mounjaro after 30 days?

The in-use window is the period the pen has been tested and licensed for after first use, so beyond it the pen's sterility and potency are no longer assured.¹ Discarding the pen is the safe course.

07 · Travelling with your pen

Travelling with Mounjaro out of the fridge

You can fly with Mounjaro, and in-use pens tolerate up to 30 days not above 30°C, so most holidays need no special arrangements.¹ The planning is mostly about heat and freezing, not about the fridge.

Carry pens in hand luggage, because hold luggage can fall below freezing. A frozen pen must never be used. Ideally keep the pen in a cool bag with the prescription label or a copy of your prescription. Check destination rules for travelling with prescription injectables before you fly.

For hot climates, use an insulated pouch. The limit is not above 30°C, so a car parked in the sun, a beach bag or a windowsill can push a pen past it quickly. Think about where the pen will actually be during the day, not just where it will be at night.

Unopened pens should still be kept in the fridge. If you are travelling for a long period and carrying spare pens, put the in-use pen in your travel bag and keep the rest cold until you need them. If an unopened pen has been out of the fridge during the trip, check with the pharmacy before using it.

A few practical habits help on any trip:

• Keep the cap on so light does not reach the pen.
• Avoid leaving the pen in a hot vehicle or in direct sun.
• Keep the prescription label or a copy with you at security.
• Pack your needles and a sharps solution for the return journey.

08 · If your pen gets warm

What happens if your Mounjaro gets warm?

If an in-use pen stays not above 30°C and within its in-use period, it is still within the licence. If it has been above 30°C, do not use it, and contact the pharmacy about what to do next.¹

The same applies to an unopened pen that has been left out: the pharmacy can advise on the specifics, using the details you give about timing and conditions.

Sort the situation into a few clear groups:

• Brief warmth, still not above 30°C, in-use pen: within the licence. Keep the cap on and continue as normal.
• Above 30°C: do not use it. If the temperature is unknown, ask the pharmacy before using it.
• Frozen at any point: do not use it.

Any new symptom after an injection should be discussed with your prescriber. You can also report suspected side effects through the MHRA Yellow Card scheme.¹⁹

09 · Has my Mounjaro gone bad?

How to know if Mounjaro has gone bad

Check both the conditions and the pen itself: the expiry date, the in-use period, the temperature the pen has been kept at, whether it has ever frozen, and whether the solution is clear and colourless; do not use it if it looks cloudy or discoloured or has particles in it.¹

Run through this list before every injection from a pen you are unsure about:

• Expiry date: is the date printed on the box still ahead of you?
• In-use period: have you passed the 30 days (not above 30°C) since you first used this pen?
• Temperature: has it stayed not above 30°C when out of the fridge?
• Freezing: has it ever been frozen, for example in hold luggage or against the back of a fridge?
• Light: has the cap stayed on?

If any answer is a worry, do not inject, and ask the pharmacy.

The patient information leaflet for the KwikPen is the reference for how to handle the pen day to day, and it is worth keeping the one that comes with each box.¹³

10 · Expired or out-of-date pens

What happens if you inject out-of-date Mounjaro?

Do not inject it. Unopened pens keep until the expiry date printed on the box, and after that date there is no supported basis for using the pen.¹

If you have already injected from a pen past its date or in-use period, do not panic and do not take an extra dose to compensate. Contact your prescriber or the pharmacy, tell them what happened and ask what to do about your next scheduled injection. If you notice any unexpected symptoms, report them via the Yellow Card scheme.¹⁹

Do not stockpile pens beyond what you will use. Repeat orders with us re-check suitability and there is no auto-shipping, so you order when you need the next pen rather than building up a pile in the fridge.

11 · Timing, missed doses and pens

Storage, missed doses and the next injection

A storage problem can leave you without a usable pen on injection day, and the missed-dose rule then decides what to do. If you miss a dose, take it as soon as you can within 4 days (96 hours) of the scheduled time, then carry on with your usual day.¹ If more than 4 days have passed, skip the missed dose entirely and take the next one on your normal day. Never take two doses within 3 days of each other.

This matters for storage because a discarded pen can delay an injection. If you have to throw a pen away, contact your prescriber about the replacement and the timing instead of improvising. You can also change your weekly injection day if needed, as long as at least 3 days (72 hours) have passed since your last dose.¹

There is no best time of day to inject. Mounjaro works the same morning or evening, with or without food. What matters is the same day each week, so pick a day and time you will remember. A fixed routine also makes it easier to remember when you started each pen.

Because tirzepatide has a half-life of about five days, it takes roughly four to five weeks to clear the system after a final dose. A short delay from a storage problem is therefore not the same as stopping treatment, but your prescriber is the right person to advise on how to restart.¹