Is an Insulin Pen Right for You?

Reusable and Disposable Pens

Insulin pens fall into two categories: reusable and disposable. Reusable insulin pens use replaceable cartridges, which usually contain 300 units of insulin each. When the cartridge is empty, or if you've stored your pen and cartridge at room temperature for more than 28 days, throw the cartridge away and insert a new one.

You don't need to load disposable insulin pens; the cartridge comes pre-loaded and is part of the pen. Simply discard the whole pen when it's empty, or if you've stored your pen and cartridge at room temperature for more than 28 days.