Representation of ICD-10 Diagnosis Codes
In practice, ICD-10 diagnoses are represented by 3- to 5-character codes with explicit decimals. Each code begins with an alphabetic character that generally corresponds to the ICD-10 chapter:
| Code | Chapter |
| A-B | Infectious and parasitic diseases |
| C | Malignant neoplasms |
| D00-D09 | In situ neoplasms |
| D50-D89 | Diseases of blood, blood-forming organs, immune mechanism |
| E | Endocrine, nutritional, and metabolic disease |
| F | Mental and behavioral disorders |
| G | Diseases of the nervous system |
| H00-H59 | Diseases of the eye and adnexa |
| H60-H95 | Diseases of the ear and mastoid process |
| I | Diseases of the circulatory system |
| J | Diseases of the respiratory system |
| K | Diseases of the digestive system |
| L | Diseases of skin and subcutaneous tissue |
| M | Diseases of the musculoskeletal system and connective tissue |
| N | Diseases of the genitourinary system |
| O | Pregnancy, childbirth, and the puerperium |
| P | Certain conditions originating in the perinatal period |
| Q | Congenital malformations, deformations, and chromosomal abnormalities |
| R | Symptoms, signs, and abnormal clinical and laboratory findings, not elsewhere classified |
| S-T | Injury, poisoning, and certain other consequences of external causes |
| V-Y | External causes of morbidity and mortality |
| Z | Factors influencing health status and contact with health services |
