An insulin pen is a medical device used by individuals with diabetes to deliver insulin. It resembles a pen and contains a cartridge filled with insulin, allowing for easy and precise dosing. Users can adjust the dose by turning a dial, making it convenient for daily use. Insulin pens come in two main types: pre-filled and reusable. Pre-filled pens are disposable and come with a set amount of insulin, while reusable pens allow users to replace the insulin cartridge. Both types are designed to make insulin administration simpler and more discreet, improving the overall management of diabetes.