Short answer: Before first use, weight-loss injection pens should be stored in the fridge at 2°C–8°C, protected from light. They must never be frozen. Once in use or out of the fridge, the time allowed at room temperature ranges from 21 days to 8 weeks depending on the product and pen type; the leaflet of your own pen is what counts.

Key takeaways

  • Unopened pens are stored in the fridge between 2–8 °C; never put them in the freezer.
  • A pen that has frozen must not be used, even once thawed, because the structure of the active ingredient is damaged.
  • In-use and room-temperature times range from 21 days to 8 weeks depending on the product and pen type.
  • Use a cool bag when travelling, and never put pens in the hold on a plane.
  • Always keep the pen cap on to block exposure to light.

GLP-1 injections are stored in the fridge, between 2–8 °C, and protected from light. They are never frozen; a pen that has frozen is not used, even once thawed. Once in use, there is a period during which a pen can stay at room temperature, and this varies by product.

This page is for general information only. Storage times can differ by country and packaging; the definitive information is in the patient information leaflet in your own box. If in doubt, ask your pharmacist.

Storing in the fridge

  • The temperature should be between 2–8 °C.
  • Keep the pen in its original box; the box protects it from light.
  • Do not put it in the ice compartment or the freezer. Shelves that touch the back wall of the fridge carry a risk of freezing.
  • The door shelves are where temperature fluctuates most; a middle shelf is safer.

How long can it stay at room temperature?

A pen that is in use can be kept below 30 °C for a certain period. This period varies by product and pen type. According to the EMA product information:

  • Mounjaro KwikPen (multi-dose pen): after first use, 30 days below 30 °C, then it is thrown away even if it has not been used up.
  • Mounjaro single-dose pen or vial: may be kept unrefrigerated below 30 °C for up to 21 days in total, then thrown away.
  • Ozempic pen: after first use, 6 weeks (4-dose pens) or 8 weeks (8-dose 0.5 mg and 1 mg pens), below 30 °C or in the fridge.
  • Wegovy FlexTouch: after first use, 6 weeks below 30 °C or in the fridge.
  • Wegovy single-dose pen: unrefrigerated below 30 °C for up to 28 days.

Once a pen has been taken to room temperature, the clock starts; putting it back in the fridge does not reset it. Writing the date it came out to room temperature on the pen is far more reliable than trying to remember later.

How do you carry it when travelling?

  • On a plane, carry it in your hand luggage. The hold carries a risk of freezing.
  • You can use a cool bag, but the ice pack must not touch the pen directly. Contact causes freezing.
  • Do not leave it in a car; in a closed car the temperature quickly goes well above 30 °C.
  • Carrying your prescription or a letter from your doctor makes security checks easier.

When should it not be used?

Do not use a pen whose contents are cloudy, have changed colour or contain particles. Also do not use products you suspect have frozen, that you know have been kept at a high temperature, or that are past their expiry date. In these cases, ask your pharmacist.

Keeping track of your pens

Haftra keeps track of the pen you have and the number of doses left, and shows whether you have a spare pen. That way you see when you need to go to the pharmacy from the app rather than by looking at the pen. It is free and can be used without creating an account.

iPhone, iPad and Apple Watch. Free.

Frequently asked questions

At what temperature are weight-loss injections kept in the fridge?

The temperature should be between 2–8 °C. Keep the pen in its original box; the box protects it from light. Do not put it in the ice compartment or the freezer.

How long can weight-loss injections stay out of the fridge?

It depends on the product and pen type, from 21 days to 8 weeks below 30 °C. A Mounjaro KwikPen lasts 30 days after first use and a Mounjaro single-dose pen or vial up to 21 days in total; an Ozempic pen 6 or 8 weeks after first use depending on the pen; a Wegovy FlexTouch 6 weeks after first use and a Wegovy single-dose pen up to 28 days. The leaflet of your own pen is what counts.

If I put it back in the fridge, does the clock reset?

No. Once a pen has been taken to room temperature, the clock starts; putting it back in the fridge does not reset it.

What should you do if the pen freezes?

Do not use it, even once thawed: freezing irreversibly damages the active ingredient. Ask your pharmacist how to dispose of it.

How do you carry it on a plane?

Carry it in your hand luggage, as the hold carries a risk of freezing. You can use a cool bag, but the ice pack must not touch the pen directly. Carrying your prescription makes security checks easier.

Sources

  • EMA product information: Mounjaro (tirzepatide)
  • EMA product information: Ozempic (semaglutide)
  • EMA product information: Wegovy (semaglutide)
  • NHS: Obesity treatment
  • MHRA (Medicines and Healthcare products Regulatory Agency)

Last reviewed: 4 August 2026