ICD-10-CM Diagnosis Coding

An ICD-10-CM code is 3 to 7 alphanumeric characters. The first 3 characters are the category; characters 4-6 add etiology, anatomic site, and severity; the 7th character is an extension.

A code must be reported to the highest level of specificity available, using the full number of characters required for that code. An incomplete code (missing a required 4th-7th character) is invalid.

The placeholder X fills an empty character position so that a required 7th character lands in the correct seventh position. It is used when a code has fewer than 6 characters but still requires a 7th-character extension.

Locate the main term (the condition, not the anatomy) in the Alphabetic Index, follow subterms and indentations to candidate codes, then always verify the code in the Tabular List and read every instructional note before assigning. Never code from the Index alone.

You look up the condition (disease, symptom, eponym, or injury) as the main term, not the anatomic site. Anatomy appears as a subterm.