Level I codes identify medical procedures and services. This system is also called Current Procedural Terminology and is defined and revised by the American Medical Association. Level I codes are composed of five numbers.
Level II codes identify medical supplies and products, such as prosthetics, ambulance services or orthotics. Level II codes contain one letter and four numbers.
Level III codes, also called local codes, are codes developed by private insurers and state Medicaid programs to identify services or products that did not have a Level I or II code. These codes were eliminated on December 31, 2003.