Insulin pen

An insulin pen is an insulin injection system for the treatment of diabetes. A pen is comprised of disposable needles, a vial of insulin, and a "pen."

Types of pens
A number of companies make insulin pens including Novo Nordisk, Aventis and Eli Lilly. These companies produce pens for most of their insulins, including humalog (also known as insulin lispro) and lantus. However, there are really only two different types of systems: replaceable cartridge and prefilled.

A replaceable cartridge pens reuses the pen portion. When the insulin is empty, the vial is simply replaced by inserting a new one.

A prefilled pen is entirely disposable. When the insulin is gone, the entire unit is discarded.

Advantages
Insulin pens have a number of advantages:
 * More convenient than traditional vial and syringe
 * Repeatedly more accurate dosages
 * Easier to use for those with visual or fine motor skills impairments.
 * Less injection pain (as polished and coated needles are not dulled by insertion into a vial of insulin before a 2nd insertion into the skin)

Disadvantages
Unlike the traditional syringe, pens are usually restricted to full or half unit dosing. In addition, insurance coverage for insulin pens in the United States may vary widely.