An insulin pen is a device for giving insulin shots. It looks like a pen. Both disposable and reusable insulin pens are available. For a reusable pen, you put the insulin cartridge into the pen. Disposable pens already have an insulin cartridge. You can set the dose of insulin with a dial on the outside of the pen. You use the pen to give the insulin shot (injection).
Insulin pens can be used instead of bottles and syringes.
Before their first use, insulin pens or insulin cartridges are stored in the refrigerator. After that, you can store them at room temperature. In general, they expire within a month after you open them. Follow the directions for storing and using the insulin.