The ICD-9-CM was an adaption maintained by the Centers for Medicare and Medicaid Services (CMS) that was used for assigning diagnostic codes associated with inpatient, outpatient, and physician office utilization.
The ICD-9-CM codes have three to five numeric characters, with the exceptions of the V codes, E Codes and M Codes that begin with a single letter.
The legacy ICD-9-CM system lacked the specificity needed to determine an exact diagnosis as the ICD-9 codes can be very broad and it became difficult to compare costs, treatments, and technologies. For that reason the ICD-9 code set was deprecated and replaced on September 30, 2015 by ICD-10 codes.
The last version of ICD-9-CM had 14,567 diagnosis codes in 20 different categories. The List of ICD-9 codes included codes for the following:
- Infectious and parasitic diseases
- Endocrine, nutritional and metabolic diseases, and immunity disorders
- Diseases of the blood and blood-forming organs
- Mental disorders
- Diseases of the nervous system
- Diseases of the sense organs
- Diseases of the circulatory system
- Diseases of the respiratory system
- Diseases of the digestive system
- Diseases of the genitourinary system
- Complications of pregnancy, childbirth, and the puerperium
- Diseases of the skin and subcutaneous tissue
- Diseases of the musculoskeletal system and connective tissue
- Congenital anomalies
- Certain conditions originating in the perinatal period
- Symptoms, signs, and ill-defined conditions
- Injury and poisoning
- External causes of injury
- Supplementary classification of factors influencing health status and contact with health services