What does “hierarchical” mean in HCC coding?
In the CMS-HCC model, related condition categories can be arranged by clinical severity and expected cost. When a patient has diagnoses that fall into more than one category within the same hierarchy, the model generally keeps the most severe category for that hierarchy instead of fully counting every related severity level.
Why does CMS use hierarchies?
Without hierarchy logic, closely related manifestations of the same disease process could be counted as though they represented completely separate levels of disease burden. CMS uses hierarchies so the model can recognize the most severe manifestation among related condition categories.
CMS explains that diagnoses are first grouped into condition categories and that hierarchies are then imposed among related categories. After hierarchy logic is applied, those categories become Hierarchical Condition Categories, or HCCs.
This is one reason memorizing a list of HCC numbers is not enough. A risk adjustment coder needs to understand the relationship between the diagnosis, the condition category, and the model structure.
How does an HCC hierarchy work?
The provider documents the patient's actual diagnoses and current clinical picture.
The coder assigns all diagnoses that are supported and reportable under the applicable rules.
Selected diagnosis codes map into condition categories under the applicable risk adjustment model.
If multiple related categories fall within the same hierarchy, the model retains the category that ranks highest in that hierarchy.
The coder's responsibility is steps 1 and 2: accurate documentation review and diagnosis coding. The model handles the hierarchy calculation.
A simple hierarchy example
CMS uses coronary artery disease as an example in its report to Congress on Medicare Advantage risk adjustment. In the 2024 CMS-HCC model, related categories are arranged from more severe to less severe within that hierarchy:
If a patient has supported diagnoses that fall into more than one of these related categories, the diagnoses are still coded appropriately. The model then applies the hierarchy so the most severe category in that hierarchy drives that portion of the risk score.
How hierarchy shows up across different disease groups
Your CRC training materials use several disease groups to reinforce the same idea: related HCCs can sit at different levels in a hierarchy, and the model keeps the higher-ranked category for payment when both are triggered during the same collection period.
In the 2024 CMS-HCC model, CKD stages are arranged hierarchically. HCC 326 (CKD stage 5) is above HCC 327 (stage 4), HCC 328 (stage 3B), and HCC 329. If a patient legitimately triggers more than one of those related CKD categories, the model applies the hierarchy.
Pressure-ulcer categories are also hierarchical. A deeper, more severe ulcer category can supersede a lower-severity pressure-ulcer category for risk-score calculation when both are present.
Cancer categories are arranged by severity as well. For example, lymphoma and other cancers rank above certain colorectal and other cancer categories in the 2024 CMS-HCC hierarchy.
Respirator dependence or tracheostomy status can sit above respiratory arrest within the same hierarchy. The diagnoses are still coded as supported; the model decides which category remains after hierarchy logic is applied.
Hierarchy is not the same thing as a disease interaction
Your CRC curriculum also distinguishes hierarchies from interactions. A hierarchy prevents related severity levels from being fully counted together. An interaction does the opposite kind of job: it can add an additional risk factor when certain significant conditions occur together and the model recognizes that combination as creating greater expected clinical risk or cost.
So, in simple terms: hierarchy can suppress a lower related HCC, while an interaction can add value for a qualifying combination of conditions. Both are model functions—not reasons for a coder to change a diagnosis that is otherwise accurately documented and reportable.
What should the coder do when two diagnoses are in the same hierarchy?
Code every diagnosis that is documented, supported, and reportable under ICD-10-CM and the applicable program rules. Do not delete a valid diagnosis simply because another diagnosis falls higher in the HCC hierarchy.
Hierarchy is a model calculation—not permission to undercode the patient's clinical picture. The chart should still accurately reflect all reportable diagnoses.
| Incorrect approach | Correct approach |
|---|---|
| “This HCC is lower, so I won't code it.” | Code all supported and reportable diagnoses. Let the model apply hierarchy logic. |
| “This diagnosis gives a higher HCC, so I'll choose it.” | Choose the ICD-10-CM code supported by the provider's documentation. |
| “Two HCCs are related, so both should increase RAF.” | Check the current model. Related categories may be subject to hierarchy. |
| “The HCC number tells me disease severity by itself.” | Use the model documentation and category description; do not infer meaning from the number alone. |
Where coders get tripped up with HCC hierarchies
One common mistake is thinking “hierarchy” means the coder should select only one diagnosis from a disease family. Another is memorizing hierarchy relationships from an older model and assuming they still apply.
A third mistake is starting with the HCC instead of the diagnosis. The correct sequence is always documentation first, ICD-10-CM second, model mapping third.
Hierarchy relationships, HCC numbers, and mappings can change when CMS updates the model. That is why a hierarchy chart from a previous model year should never replace the current official mapping and model documentation.
Read: Supported vs. Unsupported Diagnoses →
Read: Clinical Documentation Barriers →
Which CMS-HCC model is being used in 2026?
For calendar year 2026, CMS completed the three-year phase-in of the 2024 CMS-HCC model for non-PACE Medicare Advantage organizations. CMS states that 100% of those Part C risk scores are calculated using the 2024 CMS-HCC model in 2026.
The 2024 model was rebuilt around ICD-10-CM and includes revised category structures and hierarchy relationships. That makes current-model references especially important when studying hierarchy.
HCC Hierarchy FAQ
Does the higher HCC mean I should code that diagnosis?
No. The diagnosis comes from the medical record and ICD-10-CM rules. The hierarchy does not determine which diagnosis the coder chooses.
If two supported diagnoses are in the same hierarchy, do I code both?
If both diagnoses are independently documented, supported, and reportable, code them according to the applicable rules. The risk adjustment model applies hierarchy logic afterward.
Does every HCC have a hierarchy?
No. Hierarchy relationships apply to selected related categories. Use the current model documentation rather than assuming every HCC has a parent or child category.
Can hierarchy relationships change?
Yes. Model structures, mappings, and HCC relationships can change when CMS updates its risk adjustment model.
Want to practice hierarchy instead of just reading about it?
The live CRC Boot Camp is designed for focused application and review. The full CRC course gives you the complete curriculum with ongoing instructor support, more practice, and more time to build confidence with hierarchy, documentation, ICD-10-CM, and risk adjustment concepts.
Explore the CRC Boot CampView the Full CRC CourseSource note: This guide was shaped by a broader review of MediCode Bootcamp's CRC teaching materials, including the 2025 CRC Chapter 7 Risk Adjustment Models answer key, Chapter 12 Frequently Coded Conditions material, and the 2026 CRC Certification Boot Camp, then checked against current CMS risk adjustment materials. Examples here are rewritten for public education rather than copied from proprietary course questions.
Official references: CMS Report to Congress: Risk Adjustment in Medicare Advantage • CMS 2024 Model Software/ICD-10 Mappings • CMS 2026 Rate Announcement