What is ICD-9?

ICD-9 (International Classification of Diseases, Ninth Revision) is a statistical classification system used to code diagnoses, symptoms, and procedures associated with hospital utilization in the United States. It was used from 1979 until 2015 when it was replaced by ICD-10. ICD-9 was commonly used for billing and tracking morbidity and mortality statistics. It provided a standardized way to report medical information for research, reimbursement, and public health purposes.