What is ICD-10 code I63.9?

I63.9 is the ICD-10-CM diagnosis code for Cerebral infarction, unspecified. A stroke caused by a blood clot in the brain, but the specific location or type is not documented or identified. It belongs to the ICD-10-CM chapter for diseases of the circulatory system (i00-i99). I63.9 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. I63.9 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. I63.9 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. I63.9 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for I63.9?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. For I63.9, V28 maps to Ischemic or Unspecified Stroke at RAF 0.289 while V24 mapped to Ischemic or Unspecified Stroke at RAF 0.262. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting I63.9?

This is the least specific stroke code; always attempt to obtain more detailed documentation from the provider about the stroke location before using this code Review imaging reports (CT, MRI) in the medical record to determine if a more specific I63 code can be assigned Because I63.9 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

I63.9 ICD-10 Code: Cerebral infarction

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupI63.9Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the circulatory system (I00-I99) / Cerebrovascular diseases (I60-I69)

I63.9

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Cerebral infarction, unspecified

A stroke caused by a blood clot in the brain, but the specific location or type is not documented or identified.

Buddy Insight

This is the unspecified cerebral infarction code, used when documentation confirms a stroke occurred but lacks detail on the mechanism, vessel, or laterality.

CMS-HCC V28

Mapped

HCC 249

Ischemic or Unspecified Stroke

RAF 0.289

CMS-HCC V24

Mapped

HCC 100

Ischemic or Unspecified Stroke

RAF 0.262

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Mapped

HCC 100

Ischemic or Unspecified Stroke

RAF 0.0

RXHCC

Not risk-adjusted for this model/period.

RAF 0

Code Trumping

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Compare selected patient codes to show trumped or trumps impact.

Code Book Path

Official

I63Cerebral infarction

I63.9Cerebral infarction, unspecified

Inclusion Terms

Official

Stroke NOS

Excludes 2

Official

transient cerebral ischemic attacks and related syndromes (G45.-)

Related Child Codes

Official

I63.0Cerebral infarction due to thrombosis of precerebral arteries

I63.1Cerebral infarction due to embolism of precerebral arteries

I63.2Cerebral infarction due to unspecified occlusion or stenosis of precerebral arteries

I63.3Cerebral infarction due to thrombosis of cerebral arteries

I63.4Cerebral infarction due to embolism of cerebral arteries

Includes

Official

occlusion and stenosis of cerebral and precerebral arteries, resulting in cerebral infarction

Excludes 1

Official

neonatal cerebral infarction (P91.82-)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for I63.9 in this effective period.

Use Additional

Official

code, if applicable, to identify status post administration of tPA (rtPA) in a different facility within the last 24 hours prior to admission to current facility (Z92.82)

Code Also

Official

ICD-10-CM does not list Code Also instructions for I63.9 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Clear diagnosis of acute cerebral infarction (stroke) with type specified (ischemic, thrombotic, embolic, or venous)

Identification of the affected artery or vascular territory when possible (e.g., middle cerebral, cerebellar, small vessel)

Laterality documentation (right, left, bilateral, or unspecified)

Neurological deficits present on examination (e.g., weakness, speech difficulty, vision changes)

MEAT Support

HCC Buddy guidance

Clear diagnosis of acute cerebral infarction (stroke) with type specified (ischemic, thrombotic, embolic, or venous)

Identification of the affected artery or vascular territory when possible (e.g., middle cerebral, cerebellar, small vessel)

Laterality documentation (right, left, bilateral, or unspecified)

Neurological deficits present on examination (e.g., weakness, speech difficulty, vision changes)

Audit Caution

HCC Buddy guidance

Coding an acute stroke for a history of prior stroke — use I69.3xx sequelae codes for residual deficits from old strokes

Confusing TIA (G45.x) with completed stroke — TIA symptoms resolve completely within 24 hours with no infarction on imaging

Failing to capture laterality when documented, defaulting to unspecified codes unnecessarily

Not querying the provider when imaging confirms infarction but documentation uses vague terms like 'cerebrovascular accident' without specifying type

Common Mistakes

HCC Buddy guidance

I63.50 — Cerebral infarction due to unspecified occlusion/stenosis of unspecified cerebral artery; slightly more specific as it identifies occlusion/stenosis

I63.81 — Cerebral infarction due to small artery occlusion; use when lacunar stroke is documented

I63.6 — Cerebral infarction due to cerebral venous thrombosis; use when venous thrombosis is documented

G45.9 — Transient cerebral ischemic attack (TIA), unspecified; TIA is NOT a completed stroke

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is I63.9 an HCC code?

Yes. I63.9 maps to Ischemic or Unspecified Stroke under the CMS-HCC V28 risk adjustment model (and Ischemic or Unspecified Stroke under V24).

HCC Category Mapping

V28HCC 249, Ischemic or Unspecified Stroke

0.289

V24HCC 100, Ischemic or Unspecified Stroke

0.262

ESRDHCC 100, Ischemic or Unspecified Stroke

0.000

RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

MEAT Criteria for I63.9

For I63.9to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed I63.9 during that encounter, not just copy-forwarded from a problem list.

What This Code Means

I63.9 is the ICD-10-CM diagnosis code for cerebral infarction, unspecified. A stroke caused by a blood clot in the brain, but the specific location or type is not documented or identified. I63.9 sits in the ICD-10-CM chapter for diseases of the circulatory system (i00-i99), within the section covering cerebrovascular diseases (i60-i69).

Under the CMS-HCC V28 risk adjustment model, I63.9 maps to Ischemic or Unspecified Stroke (HCC 249) with a community, non-dual, aged base RAF weight of 0.289. Under the older V24 model, I63.9 mapped to the same category but with a base RAF weight of 0.262, V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

This is the least specific stroke code; always attempt to obtain more detailed documentation from the provider about the stroke location before using this code. Because I63.9 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for I63.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•This is the least specific stroke code; always attempt to obtain more detailed documentation from the provider about the stroke location before using this code
•Review imaging reports (CT, MRI) in the medical record to determine if a more specific I63 code can be assigned

Clinical Significance

This is the unspecified cerebral infarction code, used when documentation confirms a stroke occurred but lacks detail on the mechanism, vessel, or laterality. While it still maps to the ischemic stroke HCC category, using this code represents a missed opportunity for clinical specificity. Coders should query providers for additional detail whenever possible before assigning this code.

Documentation Requirements

✓Clear diagnosis of acute cerebral infarction (stroke) with type specified (ischemic, thrombotic, embolic, or venous)
✓Identification of the affected artery or vascular territory when possible (e.g., middle cerebral, cerebellar, small vessel)
✓Laterality documentation (right, left, bilateral, or unspecified)
✓Neurological deficits present on examination (e.g., weakness, speech difficulty, vision changes)
✓Imaging results (CT, MRI, CT angiography) confirming infarction
✓Temporal relationship establishing this as an acute event, not a historical or resolved condition
✓Causal mechanism when known (thrombosis, embolism, stenosis, venous thrombosis)

Excludes 2, Not included here, may code separately

transient cerebral ischemic attacks and related syndromes (G45.-)

Commonly Confused Codes

•I63.50 — Cerebral infarction due to unspecified occlusion/stenosis of unspecified cerebral artery; slightly more specific as it identifies occlusion/stenosis
•I63.81 — Cerebral infarction due to small artery occlusion; use when lacunar stroke is documented
•I63.6 — Cerebral infarction due to cerebral venous thrombosis; use when venous thrombosis is documented
•G45.9 — Transient cerebral ischemic attack (TIA), unspecified; TIA is NOT a completed stroke