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ICD-10 codes, (International Statistical Classification of Diseases and Related Health Problems, 10th Revision) are published by the World Health Organization (WHO) for morbidity coding. As their name implies, these are used worldwide. 

ICD-10-CM codes, (International Classification of Diseases, 10th Revision, Clinical Modification) are a variation of and comparable to ICD-10 codes. Developed by the National Center for Health Statistics (NCHS) these were authorized by the WHO to be used in the United States for morbidity and mortality reporting. These are used as diagnostic codes, serving as a tool for reporting basic health statics, as well as for indexing/ reporting the following:

  • medical records

  • medical care review

  • ambulatory / other healthcare programs 


There are over 69,000 ICD-10-CM code , which is

quite a jump from the approximate 13,000 ICD-9-CM


International Classification of Diseases, 10th Revision, Clinical Modification 


  1. Certain Infectious Parasitic Diseases

  2. Neoplasms

  3. Disease of the Blood & Blood-forming Organs

  4. Endocrine, Nutritional, & Metabolic Disease

  5. Mental, Behavioral, & Neurodevelopmental Disorders

  6. Disease of the Nervous System

  7. Diseases of the Eye & Adnexa

  8. Disease of the Ear & Mastoid Process

  9. Diseases of the Circulatory System

  10. Diseases of the Respiratory System

  11. Disease of the Digestive System

  12. Disease of the Skin & Subcutaneous Tissue

  13. Diseases of the Musculoskeletal System & Connective Tissue

  14. Diseases of the Genitourinary System

  15. Pregnancy, Childbirth, & the Puerperium

  16. Certain Conditions Originating in the Perinatal Period

  17. Congenital Malformations, Deformities, & Chromosomal Abnormalities

  18. Symptoms, Signs, & Abnormal Clinical & Laboratory Findings, Not Elsewhere Classified

  19. Injury, Poisoning, & Certain Other Consequences of External Causes

  20. External Caused of Morbidity

  21. Factors Influencing Health Status & Contact with Health Services 


3-7 alphanumeric characters 

(beginning with letter)

_ _ _ . _ _ _ _



  • WHO


  • NCHS (under authorization by WHO)

The ICD-10-CM manual is divided into two main parts the Index and the Tabular List. 


The Index is located at the beginning of the manual and is an alphabetical list of
terms and their corresponding codes. The main index contains the Index to Diseases and Injuries, the Neoplasm Table, and a Table of Drugs and Chemicals. The Index to External Causes of Injury follows. When selecting an ICD-10-CM code, FIRST locate the code in the Index. Then, verify the code in the Tabular List. 

Tabular List 

The Tabular List is located after the Index and is a
structured list of codes divided into twenty-one chapters, which are based on body system or condition. The chapters are further divided as follows:


  • Sections

    • Categories (3-character codes)

      • Subcategories, (4-character codes)

        • ​​​​5th, 6, and 7th character sub-classification

Code Format 

ICD-10-CM Codes range from 3 to 7 alphanumeric characters, which begin with a letter. A decimal is placed after the first three characters and four possible add-on characters follow: xxx.xxxx. The first character is always any letter (except U) and the second two characters are always numbers. The remaining 4th, 5th, 6th, and 7th characters can be alphanumeric (expect U). 

The first three characters represent the category, while the 4th, 5th, and 6th characters represent the etiology anatomical site, and severity. The remaining 7th character is an extension. 


The placeholder "X" is used in certain codes for expansion purposes, and must be used to fill in any empty spaces in cases were the 7th character must be added.  See Code Format Chart. 


Code Ranges 

ICD-10-CM Codes range from A00-Z99, representing each of the Twenty-One Chapters. See Code Ranges Chart. 



General rules for using the ICD-10-CM system known as Official Conventions are incorporated in both the alphabetic index and tabular list. Such conventions and instructions of the classification system take precedence over the guidelines and are applicable regardless of the healthcare setting.    


The back of the manual has five appendices, ranging from A-E, which provide valuable references.:

  • A) Steps to Correct Coding 

  • B) Valid 3-Character ICD-10-CM Codes

  • C) Pharmacology List

  • D) Z codes for Long-Term Drug Use with Associated Drugs and

  • E )Z Codes Only as Principle/ First Listed Diagnosis. 

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