According to the Norditropin website, all Norditropin products must be refrigerated (36°F to 46°F) prior to first use. Do not freeze and avoid direct light. After the first injection, the pens can either be stored outside of the refrigerator (up to 77°F) for use for 21 days. If stored in the refrigerator after first use the Norditropen HGH pen will last for 4 weeks. The temperature range should be between 36°F and 46°F. Never place your pens in a freezer.