Tresiba (insulin degludec) is good for 56 days after opening, which works out to 8 weeks. This applies whether you keep it at room temperature or put it back in the refrigerator. After 56 days, discard the pen or vial even if insulin remains inside.
The 56-Day Rule
Once you first use a Tresiba FlexTouch pen or puncture a vial, the clock starts on a fixed 56-day window. During that time, you can store it at room temperature (up to 86°F / 30°C) or in the refrigerator (36°F to 46°F / 2°C to 8°C). You can also switch between the two. The 56-day limit stays the same regardless of which storage method you choose.
This is notably longer than many other insulins. Most rapid-acting insulins and some basal insulins have in-use periods of 28 days. Tresiba gets the extra time because of how the molecule is built. Insulin degludec naturally forms paired clusters of six molecules while sitting in solution, and this structure keeps the insulin unusually stable at warmer temperatures for longer periods.
How to Store an Open Pen
Novo Nordisk, the manufacturer, specifies that opened Tresiba pens should be stored without a needle attached. Leaving a needle on can allow air to enter the cartridge or insulin to leak out, both of which affect dosing accuracy. Cap the pen after each use and keep it out of direct sunlight and away from heat sources like car dashboards, windowsills, or radiators.
If you refrigerate your open pen, let it warm up for a few minutes before injecting. Cold insulin can sting more and may be slightly less comfortable. There’s no need to bring it all the way to room temperature, just take the chill off.
Unopened Tresiba Storage
Before first use, Tresiba should stay refrigerated at 36°F to 46°F (2°C to 8°C) until its labeled expiration date. If an unopened pen or vial has been left out at room temperature (below 86°F), it’s still usable for up to 56 days from the date it left the fridge, but no longer than the printed expiration date, whichever comes first. Never freeze Tresiba. If it has been frozen, throw it away.
Signs That Tresiba Has Gone Bad
Tresiba should always look clear and colorless, similar to water. Before every injection, hold the pen or vial up to the light and check. Discard it immediately if you notice any of the following:
- Cloudiness or haziness in the liquid
- Color changes, such as a yellow or brownish tint
- Particles or clumps floating in the solution
- Thickened consistency that looks different from normal
Even if the insulin looks fine, do not use it past the 56-day mark. Degradation isn’t always visible, and using weakened insulin can lead to unexpectedly high blood sugar without an obvious cause.
Practical Tips for Tracking the Date
Eight weeks is long enough that it’s easy to lose track of when you opened a pen. Write the discard date directly on the pen label with a permanent marker or use a small sticker. Some people set a phone reminder for 56 days out. If you can’t remember when you opened it, the safest approach is to replace it.
For travel, Tresiba is relatively forgiving compared to other insulins. The 86°F upper limit covers most indoor environments, and you can move it in and out of a cooler or refrigerator without resetting the timer. On long flights or road trips, an insulated pouch keeps it within range without needing ice packs, as long as the ambient temperature isn’t extreme. Just avoid checked luggage on flights, where cargo hold temperatures can drop below freezing.