ICD-10-CM is a seven-character, alphanumeric code. Each code begins with a letter, and that letters followed by two numbers. The first three characters of ICD-10-CM are the “category.” The category describes the general type of the injury or disease. The category followed by a decimal point and the subcategory.
This is followed by up to 2 sub classifications, that further explain the cause. Furthermore manifestation, location, severity, and type of injury or disease. The last character is the extension.
Type Of Encounter
The extension describes the type of encounter this is. If first time a healthcare provider seen patient for this type condition, injury, disease it’s listed as the “initial encounter”. Every encounter after the first is listed as a “subsequent encounter”. Patient visits related to the effects of a previous injury or disease are listed with the term “sequela.”
To review: the first digit of an ICD-10-CM code is always an alpha. The second digit is always numeric, and digits three through seven may be alpha or numeric. Here’s a simplified look at ICD-10-CM’s format.