What is an HCC code? It's not a code you assign. See how ICD-10-CM diagnoses map to HCCs under V28, with real examples and the weights CMS gives them.
An HCC code is a Hierarchical Condition Category: a group of related ICD-10-CM diagnosis codes that CMS uses to predict a patient's health care costs. Coders don't assign HCCs. They assign ICD-10-CM codes, which map to an HCC. Under the CMS-HCC model, V28, only diagnoses mapping to one of 115 payment HCCs affect a Medicare Advantage risk score.
So "HCC code" is shorthand. The code on the claim is always ICD-10-CM. The HCC is the category it rolls up into, and each payment HCC carries a coefficient that adds to the patient's risk adjustment factor (RAF) score. How those coefficients combine into a score is worked through step by step in RAF score mechanics: coefficients, demographics and interaction terms.
How a diagnosis becomes an HCC
Here's how a handful of common diagnoses map under V28, with the coefficient for a community-dwelling, non-dual, aged Medicare Advantage member:
| ICD-10-CM code | Diagnosis | V28 payment HCC | Coefficient |
|---|---|---|---|
| E11.9 | Type 2 diabetes without complications | HCC 38 | 0.166 |
| E11.22 | Type 2 diabetes with diabetic chronic kidney disease | HCC 37 | 0.166 |
| I50.9 | Heart failure, unspecified | HCC 226 | 0.360 |
| I48.91 | Atrial fibrillation, unspecified | HCC 238 | 0.299 |
| J44.9 | COPD, unspecified | HCC 280 | 0.319 |
| E66.01 | Morbid obesity due to excess calories | HCC 48 | 0.186 |
| N18.5 | Chronic kidney disease, stage 5 | HCC 326 | 0.815 |
| I10 | Essential hypertension | None | 0 |
| E78.5 | Hyperlipidemia, unspecified | None | 0 |
| F32.9 | Major depressive disorder, single episode, unspecified | None | 0 |
Coefficients are from CMS's 2024 CMS-HCC model (V28) relative factors, which apply for payment years 2026 and 2027. A coefficient of 0.360 means the condition adds about 36 percent of an average beneficiary's expected annual cost, before normalization and other adjustments.
The last three rows matter as much as the first seven. Hypertension and hyperlipidemia are among the most common diagnoses in Medicare and carry no payment HCC. They're still coded whenever they're documented and addressed. They just don't change the risk score.
What "hierarchical" means
Related HCCs sit in families, ranked by severity. When a patient has diagnoses in two HCCs from the same family, only the most severe one counts. If a patient has both chronic kidney disease stage 4 (HCC 327) and stage 5 (HCC 326) coded in the same year, HCC 326 applies and HCC 327 drops out. Coding more diagnoses in one family doesn't add more weight.
How many HCCs are there?
Under the 2024 CMS-HCC model (V28), there are 115 payment HCCs, up from 86 in the previous V24 model. The CMS fact sheet for the model reports that 7,770 ICD-10-CM codes, about 10.5 percent of all codes, mapped to a payment HCC when V28 was introduced, down from 9,797 under V24.
That's why a patient with many documented conditions can still have only a few HCCs. Most diagnoses don't map to one.
Where HCCs are used
| Model | Program |
|---|---|
| CMS-HCC (V28) | Medicare Advantage Part C |
| ESRD CMS-HCC | Medicare Advantage members with end-stage renal disease |
| RxHCC | Medicare Part D |
| HHS-HCC | ACA individual and small group plans |
Each model has its own HCC list and coefficients. A diagnosis can map to an HCC in one model and not another.
Why HCCs reset every year
The CMS-HCC model is prospective. Diagnoses documented at qualifying face-to-face encounters in one calendar year set the next year's risk score. A chronic condition that isn't documented and addressed during the year contributes nothing, even if the patient still has it. That annual cycle is why HCC capture is ongoing work, not a one-time diagnosis.
Getting it right at scale means every HCC traces back to a supported diagnosis in a real encounter.
Related questions
Is an HCC code the same as an ICD-10 code?
No. ICD-10-CM codes are the diagnosis codes reported on claims. An HCC is a category that groups related ICD-10-CM codes for risk adjustment. Many ICD-10-CM codes map to no HCC at all.
Do HCC codes go on the claim?
No. Only ICD-10-CM codes go on the claim or encounter record. CMS maps them to HCCs when it calculates the risk score.
What is the difference between V24 and V28 HCCs?
V24 is the older 2020 CMS-HCC model with 86 payment HCCs. V28 is the 2024 model, rebuilt on ICD-10-CM, with 115 payment HCCs and fewer diagnosis codes mapped to payment. V28 has set 100 percent of Medicare Advantage risk scores since payment year 2026.
Does every chronic condition have an HCC?
No. Many common chronic conditions, including essential hypertension and hyperlipidemia, map to no payment HCC under V28. Others, such as protein-calorie malnutrition and unspecified angina, carried an HCC under V24 but don't under V28. They should still be coded whenever they're documented and addressed.
This page is general education on risk adjustment. It isn't a coding determination for any specific patient or encounter.
