Medical Coding, 2nd Edition

APPENDIX A

List of ICD-10-CM Three-Character Diagnosis Categories

Note: All valid ICD-10-CM diagnosis codes have three, four, five, or six characters. Each diagnosis falls under one of the three-character categories listed below. If a three-character category is subdivided into more specific codes with four, five, or six digits, the subdivisions must be used, not the three-character category. An example is Cholera, category A00. It is further subdivided into A00.0, A00.1, and A00.9 for different causes of cholera as well as cholera, unspecified; thus, the four-character codes must be used. NEC means “not elsewhere classified,” which means that the documented disease or condition does not have a specific code.

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