Keep unopened Lantus Solostar pens in the refrigerator. Before use, take the pen out of the refrigerator and let it come to room temperature for an hour or two. Once you have started using a pen, do not put it back in the refrigerator. It will keep for 28 days at room temperature.
If a Lantus Solostar pen has been at room temperature longer than 28 days, frozen, or gotten too hot (stored above 86 degrees Fahrenheit or left in a car on a sunny or warm day), discard it. Keep Lantus Solostar out of reach of pets and children.