Not in use (unopened): If unopened, Tresiba should be stored in a refrigerator (36°F to 46°F [2°C to 8°C]) until expiration date. It can also be stored below 86°F for 56 days. In use (opened): After first use, Tresiba can be stored at room temperature (below 86°F [30°C]) or in the refrigerator (36°F to 46°F [2°C to 8°C]) without the needle attached for a maximum of 8 weeks (56 days).