The insulin pen we often talk about is similar to the ballpoint pen we usually write with. It consists of three parts: the body, the core and the needle. Insulin liquid is filled in the pen core. When used, the pen core is put into the pen body, then the needle is installed, the dosage is selected, the skin is disinfected, the needle is inserted into the skin, and insulin injection is completed with a gentle press. Because of its convenience, simplicity and speed, it becomes the first choice for many sugar lovers.