The rules that hold for every product
- Unopened pens live in the fridge, 2 to 8 °C. That is the storage condition every one of these products is licensed under.
- Never freeze one, and never use one that has frozen. Freezing denatures the protein irreversibly. A pen that has frozen is finished even if it looks perfect after thawing, and this is not a judgement call.
- Do not store against the back wall or near the cooling element. That is the part of a domestic fridge that regularly drops below zero. The door or a middle shelf is safer than the coldest spot.
- Keep the cap on. Light matters for these formulations, and the cap is the light protection.
- Do not use a pen that looks wrong. The solution should be clear and colourless. Cloudy, discoloured or containing particles means discard it.
- Room-temperature allowance is a separate clock from the in-use window. They are different specifications with different numbers, and confusing them costs people pens.
Time out of the fridge, product by product
Every product permits a period at room temperature, and the permitted period is not the same for all of them. The two most commonly needed:
| Pen | Fridge, unopened | Room temperature allowance | In-use window |
|---|---|---|---|
| Ozempic | 2 to 8 °C | Up to 56 days at up to 30 °C | 56 days from first use |
| Mounjaro or Zepbound KwikPen | 2 to 8 °C | Up to 30 days at up to 30 °C | 30 days from first use |
| Wegovy FlexTouch | 2 to 8 °C | Check your leaflet | 42 days from first use |
| Saxenda and Victoza | 2 to 8 °C | Check your leaflet | 30 days from first use |
These are manufacturer figures and they vary by market and by formulation. Your leaflet is authoritative for the product you were actually dispensed, and your pharmacist can confirm it in a minute. Where a number is not stated here it is because it varies enough that quoting one would be misleading.
Two things follow from that table. Room-temperature time is generally counted once and does not reset by putting the pen back in the fridge, so a pen that has spent a fortnight in a bathroom cabinet has spent it. And on tirzepatide the two clocks are the same length, which means a KwikPen taken out of the fridge on day one has no margin at all.
Flying with a pen
The single rule that matters: injectable medication goes in hand luggage, never in the hold.
- The hold is not temperature controlled to your requirements. Cargo compartments on many aircraft run near or below freezing at altitude, and freezing destroys the drug.
- Lost luggage is a lost course of treatment. A delayed bag is an inconvenience for clothes and a clinical problem for medicine.
- Carry the pens in their original cartons with the pharmacy label attached. The label is what identifies the medicine as yours at security.
- Medically necessary liquids are exempt from the usual volume limits, but you have to declare them. Take them out of your bag at the checkpoint rather than hoping.
- Carry needles in the same bag as the pens, with the medicine they belong to.
- Ask your prescriber for a short letter if you are crossing borders. Name, medication including the active ingredient, dose and the fact that needles are required.
For the flight itself, a cooling wallet designed for insulin is the right tool. An ice pack in direct contact with the cartridge is not, because it can take the pen below zero, which is the one failure you cannot recover from. Wrap or separate, do not pack against.
Time zones and your injection day
Weekly drugs are forgiving here. A few hours of shift is negligible against a five or seven-day half-life, so on a normal holiday you inject on your usual day at whatever local time is convenient and ignore the arithmetic.
Long trips across many time zones deserve one decision made in advance rather than improvised at 3 am: pick either the local clock or your home clock, keep it for the whole trip, and record the day. The labels for both semaglutide and tirzepatide allow the injection day to be changed provided at least 72 hours separate two injections, which is enough room for almost any itinerary. There is more on that in choosing your injection day.
Daily medications are the ones that need thought. Saxenda and Victoza are once a day at a consistent time, and Rybelsus has a strict fasting window that a disrupted travel schedule breaks easily.
Supply arithmetic for a trip
The mistake is packing exactly enough. Pack for the trip plus a margin, because pharmacies abroad will not fill a foreign prescription on a Sunday.
- Count doses, not pens. A KwikPen with two doses left is two doses, not a spare.
- Check first-use dates before you go. A pen that expires mid-trip is a pen you cannot use on day nine.
- Take one more pen than the arithmetic requires if you have it.
- Split the supply across two bags if you are travelling with someone, so a single lost bag is not the whole course.
- Note the active ingredient, not just the brand. Tirzepatide is dispensed as Mounjaro in most of the world and as Zepbound in the United States, and a pharmacist who does not recognise the brand will recognise the molecule.
When a pen has been mistreated
Three situations, three answers.
It froze
Discard it. This is not a probability judgement. Freezing damages the protein irreversibly and the solution can look completely normal afterwards.
It got hot
Above the stated ceiling, or beyond the permitted number of days at room temperature, the manufacturer position is to discard. Degradation from heat is gradual and invisible, so there is nothing to inspect.
You are not sure
Ask your pharmacist and describe what actually happened, including how long and roughly how warm. That is a two-minute conversation and they answer it routinely.
The reason to log an excursion when it happens is that in three weeks you will not remember whether the pen you are holding is the one that sat in the car. Loss of effect with no other explanation is a real clinical question, and a record that includes a heat excursion answers it immediately.
What Penwise tracks here
For every pen you own, the app holds the first-use date, the discard date counted down, the doses remaining at your current strength and the days of supply that represents. It flags a pen whose medicine will outlast its window before you open it rather than afterwards, and it lets you note an event against a specific pen so an excursion is attached to the device it happened to.
The pen click chart covers dose delivery, and how long a pen lasts covers the in-use windows in detail.
Know which pen is which, and how long it has
First-use dates, discard countdowns and supply arithmetic for every pen you own. Free core tracker, no account.
Common questions
How long can Mounjaro be out of the fridge?
How long can an Ozempic pen stay out of the fridge?
Can I use a GLP-1 pen that has been frozen?
Can I take Ozempic or Mounjaro on a plane?
Do I need a cool bag for a GLP-1 pen?
Does putting a pen back in the fridge reset the room-temperature clock?
Sources
Every factual claim on this page traces to the product information a regulator publishes, or to a published trial. Links open on the site of whoever issued the document.
- Ozempic: EPAR product information European Medicines Agency
- Mounjaro: EPAR product information European Medicines Agency
- Wegovy: EPAR product information European Medicines Agency
Penwise is a tracking and education tool, not a medical device. Nothing on this page is medical advice, a diagnosis or a recommendation to start, stop or change a dose. Dosing decisions belong to you and your clinician. Ozempic, Wegovy, Rybelsus, Saxenda and Victoza are trademarks of Novo Nordisk; Mounjaro, Zepbound and Trulicity are trademarks of Eli Lilly. Penwise is not affiliated with, endorsed by or connected to either company.