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 as part of the CMS-HCC risk adjustment model and is the single most important reference for coders working in risk adjustment.

Of the approximately 72,000 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:

Step 1: Provider documents a diagnosis — During a face-to-face encounter, the provider identifies, evaluates, and documents the patient's conditions. The documentation must meet MEAT criteria (Monitoring, Evaluating, Assessing, Treating) for each condition to be codeable.

Step 2: Coder assigns the most specific ICD-10-CM code — The coder reviews the documentation and selects the ICD-10-CM code that most accurately and specifically represents the documented condition. Specificity is critical — unspecified codes frequently do not map to HCCs.

Step 3: The code is mapped through the CMS-HCC model — Each ICD-10-CM code is checked against the CMS mapping table. If the code maps to an HCC, that HCC is captured. If the code does not map, it contributes no risk adjustment value.

Step 4: Hierarchies are applied — When a patient has multiple HCCs within the same disease hierarchy, only the highest-severity category counts. For example, if a patient has both diabetes with chronic complications (HCC 37) and diabetes without complications (HCC 38), only HCC 37 is retained because it sits higher in the diabetes hierarchy.

Step 5: Each HCC's coefficient contributes to the Risk Adjustment Factor score — The remaining HCCs after hierarchy application each add their coefficient (weight) to the patient's demographic baseline, producing the total Risk Adjustment Factor score.

One important detail: a single ICD-10-CM code maps to exactly one HCC (or none). However, multiple different ICD-10-CM codes can map to the same HCC. For example, E11.21 (Type 2 diabetes with diabetic nephropathy), E11.22 (Type 2 diabetes with diabetic chronic kidney disease), and E11.311 (Type 2 diabetes with unspecified diabetic retinopathy with macular edema) all map to HCC 37 (Diabetes with Chronic Complications).

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:

E11.21 through E11.69 (Type 2 diabetes with specified complications) — These codes map to HCC 37 (Diabetes with Chronic Complications). This includes diabetic nephropathy, diabetic chronic kidney disease, diabetic retinopathy, diabetic neuropathy, diabetic peripheral angiopathy, and hyperglycemia.

E11.9 (Type 2 diabetes without complications) — Maps to HCC 38 in V28. This is a lower-weighted category. In V24, this mapped to HCC 19.

E10.xx (Type 1 diabetes) follows the same complication-based mapping pattern as Type 2.

Key point: The complication, not the diabetes type, determines the HCC. Specificity of the complication is what drives the mapping from HCC 38 to HCC 37.

Heart and Vascular Conditions (HCC 221, 237, 238)

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

I50.22, I50.32, I50.42 (Chronic systolic, diastolic, combined heart failure) — Map to HCC 221 (Heart Failure)

I50.9 (Heart failure, unspecified) — Maps to HCC 226 in V28, a lower-weighted category

I48.0, I48.2, I48.91 (Atrial fibrillation and flutter) — Map to HCC 238 (Specified Heart Arrhythmias) in V28

I25.10 (Atherosclerotic heart disease of native coronary artery without angina) — Check V24 vs V28 mapping differences carefully, as the HCC assignment changed between models

I11.0 (Hypertensive heart disease with heart failure) — Maps to HCC 221 through the heart failure component; code both the hypertensive heart disease code and the appropriate heart failure code

Chronic Kidney Disease (HCC 326, 329)

Chronic Kidney Disease staging directly determines the HCC category:

N18.30 through N18.32 (Chronic Kidney Disease, Stage 3) — Maps to HCC 329 in V28

N18.4 (Chronic Kidney Disease, Stage 4) — Maps to HCC 326

N18.5 (Chronic Kidney Disease, Stage 5) — Maps to HCC 326

N18.6 (End-stage renal disease) — Maps to HCC 326

N18.1 and N18.2 (Stages 1 and 2) — Do NOT map to an HCC in either model

N18.9 (Chronic Kidney Disease, unspecified) — Does NOT map to an HCC. Stage must be specified.

Respiratory Conditions (HCC 280, 283)

J44.0 (Chronic Obstructive Pulmonary Disease with acute lower respiratory infection) — Maps to HCC 280

J44.1 (Chronic Obstructive Pulmonary Disease with acute exacerbation) — Maps to HCC 280

J43.x (Emphysema codes) — Map to HCC 280

J84.10 through J84.17 (Pulmonary fibrosis) — Map to varying HCCs depending on specificity

J44.9 (Chronic Obstructive Pulmonary Disease, unspecified) — Still maps to HCC 280, but auditors prefer specific codes

Cancer (HCC 17-24)

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

C-codes (active malignancies) — Map to cancer HCCs in categories 17 through 24, depending on the organ system and severity

Z85.x (Personal history of malignant neoplasm) — Do NOT map to any HCC

The critical distinction: Active treatment vs. surveillance/remission determines whether a C-code or Z85 code is appropriate. Only code active cancer if the provider documents ongoing disease or active treatment at the current encounter.

Mental Health (HCC 151-155)

F20.x (Schizophrenia) — Maps to HCC 151 or HCC 152 depending on severity and type

F31.x (Bipolar disorder) — Maps to HCC 154

F32.x, F33.x (Major depressive disorder, single episode and recurrent) — Map to HCC 155

Severity must be specified: Mild, moderate, severe, with or without psychotic features. The code set requires this specificity.

Substance Use Disorders (New in V28)

V28 created dedicated HCC categories for substance use disorders that did not exist in V24:

F10.20 (Alcohol dependence, uncomplicated) — Maps to HCC in V28

F11.20 (Opioid dependence, uncomplicated) — Maps to HCC in V28

F12.20 through F19.20 (Other substance dependence codes) — Map to substance use disorder HCCs in V28

Critical distinction: "Use" codes (F1x.10) typically do NOT map to HCCs. Only "dependence" codes (F1x.20) map. This is the most important substance use coding distinction for risk adjustment. See our V28 changes guide for the full list of new substance use disorder categories.

Codes That Do NOT Map to HCCs (Common Surprises)

Many coders are surprised to learn that several very common diagnosis codes carry zero risk adjustment value:

E11.9 — Type 2 diabetes mellitus without complications (maps to low-weight HCC 38 in V28; no HCC in some interpretations under V24 HCC 19 deletion)

I10 — Essential hypertension (no HCC in any model version)

J06.9 — Acute upper respiratory infection, unspecified (no HCC)

M54.50 — Low back pain, unspecified (no HCC)

E78.5 — Hyperlipidemia, unspecified (no HCC)

E03.9 — Hypothyroidism, unspecified (no HCC)

M17.11/M17.12 — Primary osteoarthritis of the knee (no HCC)

G47.33 — Obstructive sleep apnea (no 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 the mapping tables annually as CSV files. These are definitive but require manual lookup, and you need to download separate files for V24 and V28 to compare both models during the blend period.

Traditional encoders: Many commercial encoders include ICD-10-CM code lookup but do not display HCC mapping information. You can find the code, but you cannot see its risk adjustment impact without a separate reference.

HCC Buddy: Built specifically for risk adjustment coders, HCC Buddy shows the HCC mapping inline with every code search. Type any ICD-10 code or search by description, and the result includes the V24 HCC, V28 HCC, Risk Adjustment Factor weights for both models, hierarchy information, and coding guidelines. Search any code at hccbuddy.com/encoder to see the mapping instantly.

V24 vs V28 Mapping Differences

During the blend period (Payment Year 2024 through 2027), both V24 and V28 mappings are financially relevant. This creates a unique challenge for coders:

Some codes map to an HCC in V24 but NOT in V28 — These codes are losing value as the V28 blend weight increases each year

Some codes map to an HCC in V28 but NOT in V24 — These codes are gaining value, particularly the new substance use disorder categories

Some codes map to DIFFERENT HCCs in V24 vs V28 — The category number and weight may both be different

Coders must check both models to understand the full risk adjustment impact of each code they assign

Use HCC Buddy to see both V24 and V28 mappings side by side for every code search. For a comprehensive overview of what changed between models, see our Complete Guide to HCC V28 Changes for 2026.

Conclusion

ICD-10 to HCC mapping is the bridge between clinical documentation and risk adjustment reimbursement. Understanding which codes map, which do not, and how mappings differ between V24 and V28 is the core competency of a risk adjustment coder.

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.

Get instant ICD-10 to HCC mapping for any code — start your 14-day Pro trial with no credit card required. See V24 and V28 mappings, Risk Adjustment Factor weights, hierarchy information, and coding guidelines on every search.

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

ICD-10 to HCC Mapping Quick Reference