What Temperature Should You Keep Mounjaro At? (October 2026)

01 · The short answer

What temperature should you keep Mounjaro at?

Keep unused Mounjaro pens in a fridge running at 2–8°C, in the carton they came in, until the day you start them.¹³ That is the whole rule for pens you are not using yet. Once a pen is in use, the licence allows it to be kept out of the fridge for up to 30 days (not above 30°C).¹

Mounjaro is a once-weekly injectable prescription medicine made by Eli Lilly, and it comes as a pre-filled multi-dose pen in strengths from 2.5mg to 15mg.¹ The storage rules are the same whichever strength you have been prescribed.

Our guide to what temperature to store Mounjaro covers the essentials.

02 · Quick reference

Mounjaro storage rules by situation

03 · What next

Do I need to do anything else?

For most people the routine is simple: fridge for spare pens, a sensible cool place for the pen you are using, and a quick check of the pen before each weekly injection. If you are still weighing up whether treatment is right for you, our weight loss clinic explains the options.

04 · Unopened pens

Storing unopened Mounjaro pens

Unopened pens should be kept in the fridge at 2–8°C until you are ready to start them, and they keep until the printed expiry date.¹³ The expiry date is on the carton and the pen label. Always go by that date, not by when you think the pen arrived.

Leave each pen in its original carton while it is in the fridge. Keeping the carton on also keeps the label and batch details with the pen, and the pen cap protects it from light.

Where you put the pens in the fridge matters as well. Never let pens freeze, so keep them away from the freezer compartment.

If you are not sure your fridge holds the right range, a basic fridge thermometer is a small accessory purchase and takes the guesswork out.

Keep pens somewhere children cannot reach. A fridge that is shared with others, a student house for example, is a good reason to keep the pens inside their carton and perhaps in a small closed container as well.

05 · The in-use pen

Storing the pen you are currently using

Once you have started a KwikPen, the UK licence allows it to be kept out of the fridge for up to 30 days (not above 30°C).¹ The 30 days is the limit, so the pen should be discarded at the end of that period whether or not any medicine is left.

Many people find it practical to keep the in-use pen in the fridge anyway. It removes any doubt about heat, and the pen is there on injection day. If you do keep it at room temperature, choose somewhere cool and dry, away from radiators, windowsills, kitchen worktops beside the kettle or oven, and out of direct sunlight. A drawer in a bedroom or hallway is usually fine; a hot car is not.

It helps to write the date you first used the pen on the carton or in your phone. That makes the 30-day limit easy to check, and apps such as GLPTrackr, our free companion app, let you track injection dates across your whole treatment.

Keep the cap on between injections. Follow the instructions supplied with the pen for attaching and removing the needle, and put used needles in the sharps bin that comes with your order.

06 · Why 30 days

Why you cannot use Mounjaro after 30 days (not above 30°C)

Once in use, a pen can be kept out of the fridge for up to 30 days at a temperature not above 30°C; beyond that, sterility and potency are no longer assured.¹

If you ever find a pen with medicine left at the end of the window, the answer is still to discard it. Using a pen past the limit is outside the licence.

If you think your pen has lost doses, or if there seems to be too little left for a full dose, contact your prescriber or pharmacy. Do not combine the remains of two pens.

07 · Warm or left out

What happens if Mounjaro gets warm or is left out?

If Mounjaro gets warm or has been left out of the fridge, do not inject it on a guess: check the leaflet and speak to your pharmacy. Heat can damage the medicine, and warmth does not always leave a visible sign.¹³

The honest answer to "how long can Mounjaro be at room temperature?" depends on whether the pen is unopened or in use. An in-use pen has the 30-day licence window.¹ For an unopened pen that has been out of the fridge, check with your pharmacy before using it rather than relying on a remembered day limit.

When you contact the pharmacy, have the following ready:

• the strength and the batch number on the carton
• where the pen was left and roughly for how long
• whether it was in direct sun, a hot car or near a heater
• whether the pen is unopened or already in use
• whether the pen looks any different from normal

08 · Freezing and damage

Frozen pens and how to tell if Mounjaro has gone bad

A pen that has frozen must not be used. The leaflet says Mounjaro must not be frozen, and a pen that has been frozen should be thrown away.¹³

Before every injection, look at the pen and the medicine. The solution inside a genuine pen is clear and colourless; do not use a pen that looks cloudy or discoloured or has particles in it.¹³ Warning signs that mean you should stop and call the pharmacy rather than inject include:

• the medicine looks different from the description in the leaflet
• the pen is cracked, leaking or visibly damaged
• the printed expiry date has passed
• you have used the pen for longer than the in-use window
• you know the pen was frozen or exposed to heat

You cannot reliably tell by eye that a pen is fine, so the history of the pen matters as much as its appearance. If a pen looks normal but you know it spent a long time somewhere hot, treat it as uncertain and ask.

If you notice new or unusual symptoms after an injection, tell your prescriber, and you can report suspected side effects through the MHRA Yellow Card scheme.¹⁹ Seek immediate medical help for severe, persistent stomach pain that may spread to your back, with or without vomiting (possible pancreatitis); pain in the upper right abdomen, fever or yellowing of skin or eyes (possible gallbladder problems); or signs of a severe allergic reaction such as swelling of the face or throat and difficulty breathing. Our page on Mounjaro side effects and temperature covers how the two topics relate.

09 · Delivery and travel

Mounjaro deliveries, travel and flying

When your order arrives, take the pens out of the box and put them in the fridge straight away. Our orders go out in discreet, temperature-controlled packaging with free next-day tracked delivery, and we dispatch the same day when you order by 3pm.

If you will not be home, arrange a safe place or another person to receive the parcel, or choose a delivery option that suits you. A parcel left in a porch on a hot day is exactly the kind of exposure to avoid. If a delivery looks as though it has been left out for a long time, tell us before you use the pens.

Generally yes, as a prescription medicine for personal use, but check the rules of your airline and airport. Practical points that help:

• carry the pen in your hand luggage, not in the hold, so it stays with you and away from freezing or extreme heat
• keep it in the original carton with the pharmacy label showing your name
• use a small insulated pouch for hot destinations, and keep it away from direct ice, so the pen does not freeze
• put it in the hotel fridge on arrival if you are staying for a while, away from the freezer section

In-use pens tolerate up to 30 days not above 30°C, so most holidays need no special arrangements.¹ For unopened spare pens, the fridge rule applies, so plan how you will keep them cool and ask the pharmacy for advice on longer trips.

10 · Fridge or not

Do you keep Mounjaro in the fridge after opening?

You do not have to keep an opened Mounjaro pen in the fridge, but you may, and many people do. The licence allows up to 30 days (not above 30°C) out of the fridge once the pen is in use.¹

Keeping the pen at room temperature is perfectly acceptable within the window. It is convenient if you travel often or inject away from home. Just keep the location cool, dry and out of the sun.

If you want a deeper look at each side, see should I keep Mounjaro in the fridge after opening, is it better to keep Mounjaro in the fridge, and do you keep Mounjaro in the fridge.

11 · Other medicines

Is Wegovy stored the same way?

Wegovy has its own storage instructions, and you should follow the leaflet supplied with it rather than assume it matches Mounjaro. Wegovy is a different medicine, semaglutide, with a pen dose ladder of 0.25mg, 0.5mg, 1mg, 1.7mg and 2.4mg once weekly.¹⁸ The right storage figure is the one printed on the product information for the pen you hold.

The general principle is the same for any injectable pen medicine: read the leaflet for your exact product, keep it in its carton, protect it from heat and freezing, and ask the pharmacist if anything is unclear. If you switch between products, do not carry storage habits from one to the other without checking.

12 · After you stop

Spare pens, expiry and stopping treatment

Spare pens in the fridge should be used in date order, with the earliest printed expiry first. Do not use any pen past its expiry date, and do not keep pens beyond what you need. Repeat orders re-check suitability and there is no auto-shipping from us, so you are in control of how many pens you hold at a time.

If you stop treatment with pens left over, do not throw them in household waste. Ask your pharmacy how to dispose of medicines and used needles safely. Sharps go in a sharps bin, which we include with every order along with injection guidance.

Tirzepatide has a half-life of about five days, so after a final dose it takes roughly four to five weeks to clear the system. Nothing needs doing while it clears, and there is no way to speed it up.¹

Mounjaro is a prescription-only medicine, supplied only after an online consultation reviewed by a GPhC-registered prescriber. It is used alongside a reduced-calorie diet and increased physical activity. Individual results vary. This page is information, not a substitute for medical advice. We are a GPhC-registered pharmacy (9012878), and our support team can help with storage questions Monday to Friday, 9am to 5pm, by email at support@everydaymeds.co.uk, through the account portal chat or on 0333 207 0413.