ICD-10 to HCC Mapping Quick Reference

What Is ICD-10 to HCC Mapping?

ICD-10 to HCC mapping is the crosswalk, the translation layer, between the ICD-10-CM diagnosis codes that medical coders assign and the Hierarchical Condition Categories that CMS uses to calculate risk adjustment payments. This crosswalk is published annually by CMS on the risk-adjustment model software and ICD-10 mappings page and is the single most important reference for coders working in risk adjustment.

Of the approximately 74,000 ICD-10-CM codes in the code set, only a subset map to HCC categories. The rest are considered "non-HCC" codes, they are valid diagnosis codes but do not contribute to a patient's Risk Adjustment Factor score. Understanding which codes map and which do not is fundamental to effective risk adjustment coding.

For a deeper explanation of how the mapping process works end-to-end, see our complete ICD-10-CM to HCC mapping guide. If you are new to HCC coding entirely, our beginner's guide covers the foundational concepts.

How the Mapping Works

The ICD-10 to HCC mapping follows a predictable sequence from clinical encounter to Risk Adjustment Factor score:

Many ICD-10-CM codes map to one HCC or none, and multiple codes can map to the same HCC. Some codes map to more than one category. E11.621, Type 2 diabetes with foot ulcer, maps to HCC 37 and HCC 383 in the CMS V28 file. E11.311 maps to HCC 37 and HCC 298. By comparison, E11.21 and E11.22 map to HCC 37 and need separate manifestation or stage codes when the Tabular instructions require them.

Quick Reference: Major Disease Categories and Their HCC Mappings

The following sections provide a practical quick reference for the most commonly encountered disease categories in risk adjustment coding. All mappings reference the V28 model unless otherwise noted. Use HCC Buddy's encoder to verify any specific code's mapping in real time.

Diabetes (HCC 37, HCC 38)

Diabetes is the single most commonly coded HCC category in risk adjustment. The distinction between complicated and uncomplicated diabetes is the key mapping determinant:

Heart and Vascular Conditions (HCC 226, 238)

Cardiac conditions are among the highest-weighted HCCs in the model:

Chronic Kidney Disease (HCC 326, 329)

Chronic Kidney Disease staging directly determines the HCC category:

Respiratory Conditions (HCC 280, 283)

Cancer (HCC 17-24)

Cancer HCCs carry some of the highest Risk Adjustment Factor weights in the model:

Mental Health (HCC 151-155)

Substance Use Disorders (Expanded in V28)

V28 expanded and renumbered the substance use disorder HCCs (V24 already captured them under HCC 54-56):

Codes That Do NOT Map to HCCs (Common Surprises)

Many coders are surprised to learn that several very common diagnosis codes do not map to an HCC:

The pattern is clear: many of the most commonly diagnosed conditions in primary care are NOT risk-adjusting. This means that from a risk adjustment perspective, the value of a coder lies in accurately capturing the less common but HCC-relevant conditions that are often buried in complex charts.

How to Look Up Mappings Efficiently

There are several ways to determine whether an ICD-10-CM code maps to an HCC:

CMS official mapping files: CMS publishes annual mapping tables. The current 2026 Final file includes generic V28 but no generic V24 column. Historical PY2025 V24 comes from the CMS 2025 Midyear/Final file.

Commercial encoders: HCC mapping, calculators and references vary by product, subscription and add-on. Check the package and source period you would actually use; see the sourced comparison.

HCC Buddy: Type an ICD-10-CM code or description to see the CY2026 V28 result, the historical PY2025 V24 reference, and the source status. RAF factors appear only when the corresponding source is verified.

V24 vs V28 Mapping Differences

During the non-PACE blend period (CY2024 through CY2025), both V24 and V28 mappings were financially relevant. CY2026 non-PACE risk scores use V28 at full weight. This creates a unique challenge for coders:

Use HCC Buddy to compare CY2026 V28 with a historical PY2025 V24 reference. For older RADV work, use the official mapping for the audited payment year. PACE requires its own CY2026 blend.

Conclusion

ICD-10-CM to HCC mapping is model- and payment-year specific. Coders need to distinguish a verified mapping, a verified no-map, and missing source evidence before applying hierarchy or RAF logic.

The single most important takeaway: specificity drives HCC capture. Unspecified codes almost never map to the highest-value HCC categories, and many do not map at all. Every coding decision should prioritize the most specific code supported by the documentation.

Check the source-labeled CY2026 V28 result and historical PY2025 V24 reference in the encoder. Unsupported mappings or factors are not shown.

Free resource: Download the HCC Coding Cheat Sheet, a printable V28 quick reference with top HCC categories, common non-HCC codes, and documentation tips.