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V28 HCC 399

Major Head Injury without Loss of Consciousness

Under the CMS-HCC V28 risk adjustment model (PY2026 Medicare Advantage), HCC 399 has a source-labeled community non-dual aged reference coefficient of 0.199, and 189 ICD-10-CM diagnosis codes appear in its official mapping. In the V28 hierarchy it is superseded by HCC 397, HCC 398 when a more severe category in the same disease group is also present.

By the HCC Buddy Coding Team · Reviewed: May 30, 2026
V28 HCC 399Community non-dual aged reference coefficient 0.199
See ICD-10-CM codes for HCC 399Open the RAF Calculator

RAF factors

The community factor varies by Medicaid and originally-disabled status; the institutional factor applies to long-term-institutional members. These are the CMS-HCC V28 PY2026 relative factors.

Community NA: 0.199Community PBA: 0.128Community FBA: 0.349Community ND: 0.15Community PBD: 0.052Community FBD: 0.19Institutional: 0.085

These are source-labeled code-level HCC coefficient references, not a full member score. Use the RAF Calculator with complete member context for CMS-HCC V28 PY2026. No score is shown unless every required source and calculation check passes.

V28 hierarchy

Trumped by: HCC 397, HCC 398 (a more severe category in the same disease group supersedes this one).

ICD-10-CM codes that map to HCC 399 (189)

ICD-10-CM codes in the official mapping for this category under CMS-HCC V28 PY2026. Open any code for its full description and coding guidance.

Coder workflow notes

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Frequently asked questions

What is CMS-HCC V28 category 399?

HCC 399 is "Major Head Injury without Loss of Consciousness", a Hierarchical Condition Category in the CMS-HCC V28 risk adjustment model (100% phase-in for payment year 2026). 189 ICD-10-CM codes appear in its official mapping.

What reference coefficient is published for HCC 399?

The source-labeled community non-dual aged reference coefficient for CMS-HCC V28 category 399 is 0.199. The exact coefficient varies by enrollment segment (community Medicaid and originally-disabled status, and institutional); the full segment table is published in the CMS V28 model files.

How many ICD-10-CM codes map to HCC 399?

189 ICD-10-CM diagnosis codes appear in the official mapping for CMS-HCC V28 category 399 (Major Head Injury without Loss of Consciousness) for payment year 2026.

Which categories trump HCC 399 in the V28 hierarchy?

HCC 399 is superseded by HCC 397 (Major Head Injury with Loss of Consciousness > 1 Hour), HCC 398 (Major Head Injury with Loss of Consciousness < 1 Hour or Unspecified). When a more severe category in the same disease group is documented, it is counted instead of HCC 399.

Related references

Sources

CMS ICD-10-CM order-file billability plus the published mapping and CMS-HCC V28 PY2026 model software. CMS-HCC V28 model published at CMS.gov Risk Adjustors; ICD-10-CM member codes from the CMS ICD-10-CM code set.

Verified current to CMS-HCC V28, payment year 2026 — last reviewed May 30, 2026.