Storage and temperature excursions: the label limits for every pen and vial, and what to do when one is broken

Storage rules are the part of the label most people read once, in the car park outside the pharmacy, and never again. Then a pen gets left on the kitchen counter, a vial goes in a suitcase, or a power cut takes the fridge out for a day, and the question becomes urgent. This guide sets out every limit on the four current labels in one place, then walks through what to do when one has been crossed.

Before first use: the refrigerator

Every product is stored in a refrigerator at 2 to 8 C (36 to 46 F) until first use, in the original carton to protect it from light. The Wegovy and Ozempic labels add two specifics worth taking literally: do not store the pen in the freezer, and do not store it directly adjacent to the refrigerator cooling element. The back wall and the chiller drawer of a domestic fridge can both drop below 2 C, and a pen touching the back wall can freeze while the milk in the door stays liquid. A middle shelf, in the carton, away from the back, is the safe spot.

The room-temperature allowances

Each label permits a period out of the fridge. They differ, and the differences matter.

Three things are true of every row. The upper limit is 30 C (86 F); no label allows anything warmer for any length of time. The allowances are cumulative for the presentations that can go back in the fridge: a Zepbound pen that spent 5 days out in June and 10 in July has 6 left. And the clock and the expiry date run independently; whichever arrives first wins.

The in-use clocks

Multi-dose pens carry a second limit that has nothing to do with temperature. An Ozempic pen or a Wegovy FlexTouch pen is discarded 56 days after first use, refrigerated or not, doses remaining or not. A Zepbound or Mounjaro KwikPen or multi-dose vial is discarded 30 days after first use or after 4 weekly doses, whichever comes first. Write the first-use date on the carton the day you open it. A pen started on the first of the month and used weekly will be finished before either limit; a pen used irregularly may not be.

Freezing

Every label says do not freeze and do not use if frozen. There is no thaw-and-check exception. Peptides such as semaglutide and tirzepatide can aggregate or degrade on freezing, and the solution can look normal afterwards. If a pen or vial has been frozen, or you find ice crystals in the carton, or it was touching the back wall of a fridge that also froze the lettuce, it is finished. Call the manufacturer or pharmacy about a replacement; this is a recognised reason for one.

Light and heat

The labels say to keep the product in the original carton to protect it from light and to protect it from heat. That excludes windowsills, dashboards, radiators, and the top of the fridge where the compressor vents. It also means the carton is part of the storage system, not packaging to throw away.

What to do after an excursion

Work through these in order.

1. Establish what happened. How long was it out, and how warm did it get? "Overnight on the counter in a house at 70 F" is a known quantity. "In the car in August" is not; a closed car interior can exceed 50 C, and the labels say nothing about any temperature above 30 C.

2. If the temperature stayed at or below 30 C (86 F). Count the hours or days against the allowance in the table and any previous time out of the fridge. If you are inside the limit, put it back in the fridge (if the presentation allows) and write down the days used. If you are over the limit, discard it.

3. If the temperature went above 30 C, or you do not know. The label gives no cover. Do not inject it on the assumption that it is probably fine. Call the number on the label (Lilly, Novo Nordisk) or the dispensing pharmacy with the details. Manufacturers hold stability data beyond what the label prints and will tell you what to do; pharmacies can often replace a pen once.

4. If there is any chance it froze. Discard, as above.

5. Look at it anyway. The Zepbound label says the solution should be clear and colourless to slightly yellow and not to use it if you see particles or discolouration; Wegovy's says clear and colourless. A pen that has changed appearance is finished regardless of the temperature history. A pen that looks normal is not proved fine by looking normal.

6. Do not double up. If an excursion costs you a dose, the missed-dose rules on the label apply (Zepbound and Mounjaro: within 4 days; Wegovy: if the next dose is more than 2 days away; Ozempic: within 5 days), and they never include taking two doses to make up. The missed-dose entry in the glossary has the exact wording.

Power cuts and fridge failures

A closed domestic fridge holds temperature for a few hours; the food-safety rule of thumb is about 4 hours unopened. A pen in a fridge that has been off for a working day has most likely stayed under 30 C in a temperate climate and has used one day of its room-temperature allowance. A fridge that failed silently over a week and warmed to room temperature has used seven days. A fridge that was left open in a hot kitchen is an unknown. Apply the steps above.

A small fridge thermometer, placed at pen height, turns most of these unknowns into knowns for very little money.

Compounded vials

None of the tables above applies to compounded semaglutide or tirzepatide. Compounded products are not FDA approved and are not interchangeable with the brand products; their storage instructions and beyond-use date are set by the dispensing pharmacy under compounding standards, and the FDA's compounding questions-and-answers page explains that a beyond-use date is not the same thing as a manufacturer's expiry date and is generally shorter. Follow the pharmacy label. If it is silent on room-temperature allowances, assume there are none and ask. FormBlends' semaglutide and tirzepatide pages describe how its pharmacies ship and label their vials.

Taking it on the road

Everything above is the basis for the travel guide, which covers the TSA rules, insulated cases, and how to count the days when a trip takes you through three climates.