In this quick, beginner-level ICD-10-CM demo, I walk through how to look up the diagnosis code for polyneuropathy using the ICD-10-CM book. This is an introductory example focused on understanding how code lookup works and not the full complexity of real-world medical coding. In practice, medical coding involves guidelines, documentation review, and clinical judgment. Coders use a variety of tools including paper code books, eBooks, and specialized coding software. This short focuses on masterin