ICD-10-CM chapters
The 22 chapters of the FY2026 ICD-10-CM tabular list. Each chapter shows how many of its codes risk-adjust under CMS-HCC V28 for payment year 2026. Open a chapter for its HCC categories and member codes.
Browse all 22 chapters
In ICD-10-CM chapter order. The count is how many codes in the chapter map to a CMS-HCC V28 payment category.
- A00-B99Certain infectious and parasitic diseases114 codes13 HCCs
- C00-D49Neoplasms1210 codes7 HCCs
- D50-D89Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism141 codes11 HCCs
- E00-E89Endocrine, nutritional and metabolic diseases570 codes13 HCCs
- F01-F99Mental, Behavioral and Neurodevelopmental disorders560 codes13 HCCs
- G00-G99Diseases of the nervous system254 codes20 HCCs
- H00-H59Diseases of the eye and adnexa56 codes3 HCCs
- H60-H95Diseases of the ear and mastoid process0 codes0 HCCs
- I00-I99Diseases of the circulatory system886 codes22 HCCs
- J00-J99Diseases of the respiratory system123 codes9 HCCs
- K00-K95Diseases of the digestive system189 codes9 HCCs
- L00-L99Diseases of the skin and subcutaneous tissue423 codes7 HCCs
- M00-M99Diseases of the musculoskeletal system and connective tissue1208 codes10 HCCs
- N00-N99Diseases of the genitourinary system8 codes5 HCCs
- O00-O9APregnancy, childbirth and the puerperium0 codes0 HCCs
- P00-P96Certain conditions originating in the perinatal period110 codes14 HCCs
- Q00-QA0Congenital malformations, deformations and chromosomal abnormalities74 codes4 HCCs
- R00-R99Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified60 codes9 HCCs
- S00-T88Injury, poisoning and certain other consequences of external causes2198 codes21 HCCs
- V00-Y99External causes of morbidity43 codes1 HCCs
- Z00-Z99Factors influencing health status and contact with health services72 codes13 HCCs
- U00-U85Codes for special purposes0 codes0 HCCs
Frequently asked questions
How is the ICD-10-CM tabular list organized into chapters?
The FY2026 ICD-10-CM tabular list is divided into 22 chapters. Each chapter covers a body system or category of conditions and spans a contiguous range of code prefixes, for example I00 to I99 for the circulatory system. HCC Buddy lists every chapter with the number of codes in it that risk-adjust under CMS-HCC V28.
Which ICD-10-CM chapters carry the most HCC risk-adjusting codes?
Neoplasms (C00-D49), endocrine and metabolic conditions (E00-E89), mental and behavioral conditions (F01-F99), and circulatory conditions (I00-I99) contribute the largest share of CMS-HCC V28 payment categories. Open any chapter below to see its exact count and the HCC categories its codes map to.
Do all ICD-10-CM codes affect the RAF score?
No. Of the roughly 72,000 FY2026 ICD-10-CM codes, only a subset map to a CMS-HCC V28 payment category and contribute to a patient's risk adjustment factor (RAF) score. Each chapter page shows how many of its codes risk-adjust and which HCC categories they hit.
Source: FY2026 ICD-10-CM Tabular (CDC/NCHS) and the CMS-HCC v28 PY2026 mapping file.