What is the difference between ICD-9-CM and ICD-10-CM

by  Christine Woolstenhulme, QCC, QMCS, CPC, CMRS
February 23rd, 2015

ICD-10-CM uses 3–7 alpha and numeric digits and full code titles, but the format is very much the same as ICD-9-CM (for example, ICD-10-CM has the same hierarchical structure as ICD-9-CM).
The 7th character in ICD-10-CM is used in several chapters (for example, the Obstetrics, Injury, Musculoskeletal, and External Cause chapters). It has a different meaning depending on the section where it is being used (for example, in the
Injury and External Cause sections, the 7th character classifies an initial encounter, subsequent encounter, or sequelae (late effect).
Primarily, changes in ICD-10-CM are in its organization and structure, code composition, and level of detail.

ICD-9-CM Diagnoses Codes:

  • Are 3–5 digits;
  • The first digit is alpha (E or V) or numeric (alpha characters are not case sensitive);
  • Digits 2–5 are numeric; and
  • A decimal is used after the third character.


• 496 – Chronic airway obstruction, not elsewhere classified (NEC);

•511.9 – Unspecified pleural effusion; and

•V02.61 – Hepatitis B carrier.


ICD-10-CM Diagnosis Codes:

  • Are 3–7 digits;
  • Digit 1 is alpha;
  • Digit 2 is numeric;
  • Digits 3–7 are alpha or numeric (alpha characters are not case sensitive); and
  • A decimal is used after the third character.


•A78 – Q fever;

•A69.21 – Meningitis due to Lyme disease; and

•S52.131A – Displaced fracture of neck of right radius, initial encounter for closed fracture



What is the difference between ICD-9-CM and ICD-10-CM. (2015, February 23). Find-A-Code Articles. Retrieved from https://www.findacode.com/articles/what-is-the-difference-between-icd-9-cm-and-icd-10-cm-2683.html

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