G45.9 ICD-10-CM Code: Transient cerebral ischemic attack, unspecified
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FY 2026 Apr update / Diseases of the nervous system (G00-G99) / Episodic and paroxysmal disorders (G40-G47)
G45.9
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceTransient cerebral ischemic attack, unspecified
A temporary interruption of blood flow to the brain that causes stroke-like symptoms but resolves completely within 24 hours, with no permanent brain damage. This code is used when the specific type or location of the transient ischemic attack (TIA) is not documented.
CMS-HCC V28
00
RAF 0
CMS-HCC V24
00
RAF 0
ACA/HHS
00
RAF 0
ESRD/PACE
00
RAF 0
RXHCC
00
RAF 0
Code Trumping
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Code Book Path
Inclusion Terms
Official- Spasm of cerebral artery
- TIA
- Transient cerebral ischemia NOS
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for G45.9 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for G45.9 in this effective period.
Excludes 1
Official- neonatal cerebral ischemia (P91.0)
- transient retinal artery occlusion (H34.0-)
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for G45.9 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for G45.9 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for G45.9 in this effective period.
Buddy Documentation Tip
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 G45.9 an HCC code?
No. G45.9 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
Coder workflow notes
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This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).
What This Code Means
G45.9 is the ICD-10-CM diagnosis code for transient cerebral ischemic attack, unspecified. A temporary interruption of blood flow to the brain that causes stroke-like symptoms but resolves completely within 24 hours, with no permanent brain damage. This code is used when the specific type or location of the transient ischemic attack (TIA) is not documented. G45.9 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering episodic and paroxysmal disorders (g40-g47).
G45.9 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
Use G45.9 only when the documentation does not specify the type of TIA (such as vertebrobasilar, carotid, or cerebral); if a specific type is documented, use the more specific G45.0-G45.8 codes instead.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for G45.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use G45.9 only when the documentation does not specify the type of TIA (such as vertebrobasilar, carotid, or cerebral); if a specific type is documented, use the more specific G45.0-G45.8 codes instead
- •Ensure the clinical record confirms the symptoms resolved completely and imaging ruled out acute stroke; TIAs are often called 'warning strokes' and warrant documentation of follow-up care and risk factor management