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ICD-10: Definition and Healthcare Context
Full name: International Classification of Diseases, 10th Revision
ICD-10 is a medical coding system used to classify diagnoses, symptoms, and medical procedures. The World Health Organization maintains ICD-10 globally; the United States uses two adaptations — ICD-10-CM (Clinical Modification) for diagnoses, maintained by the CDC, and ICD-10-PCS (Procedure Coding System) for inpatient procedures, maintained by CMS. ICD-10 replaced ICD-9 for U.S. HIPAA transactions in October 2015. ICD-10-CM contains over 70,000 diagnosis codes used on all HIPAA-covered claims.
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Last updated: 2026-07-11Reviewed by: Dr. Jennifer Montecillo, MD — Gullas College of Medicine, 2019. Non-practicing medical reviewer.
How it’s used
- Healthcare Cost Report Information System (HCRIS): hospital cost reports capture diagnosis-related group assignments derived from ICD-10-CM diagnosis codes on claims.
- CMS Care Compare: quality measures on Care Compare for nursing homes, hospitals, and dialysis facilities are derived from ICD-coded claims data.
Frequently asked questions
- What is ICD-10?
- ICD-10 is the 10th revision of the International Classification of Diseases — a coding system used to classify diagnoses (ICD-10-CM) and inpatient procedures (ICD-10-PCS) on health care claims.
- When did the US switch from ICD-9 to ICD-10?
- The US transitioned from ICD-9-CM to ICD-10-CM/PCS on October 1, 2015, under the HIPAA Administrative Simplification requirements.
- What is the difference between ICD-10-CM and ICD-10-PCS?
- ICD-10-CM contains over 70,000 diagnosis codes maintained by CDC. ICD-10-PCS contains procedural codes for inpatient hospital procedures maintained by CMS.