HCC Hierarchical Condition Category
A group of related diagnosis codes with similar expected cost, used in risk adjustment models such as the CMS-HCC model for Medicare Advantage.
A Hierarchical Condition Category (HCC) groups ICD-10-CM diagnosis codes that are clinically related and predict similar healthcare costs. Risk adjustment models — most prominently the CMS-HCC model for Medicare Advantage — use HCCs to calculate a member's risk score.
Key concepts
- Mapping: many diagnosis codes map to an HCC, but many do not map to any payment HCC.
- Hierarchies: when a patient has several related HCCs, only the most severe is counted.
- Coefficients: each HCC carries a weight that adds to the risk adjustment factor (RAF).
- Annual capture: diagnoses must be documented and coded from qualifying encounters each year to count.
Model versions
CMS has used several versions of the CMS-HCC model. The 2024 model, commonly called V28, was phased in from payment year 2024 and fully applied in 2026. Mappings and coefficients change, so always check the current CMS mapping file.
Compliance
HCCs must be supported by documentation from the encounter. Unsupported diagnoses are a focus of RADV audits and enforcement. See our HCC coding guide.