F43.9 ICD-10-CM Code: Reaction to severe stress, unspecified
F43.9 is not a CMS-HCC payment code. MEAT criteria · RAF Calculator · HCC Buddy coding tools
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FY 2026 Apr update / Mental, Behavioral and Neurodevelopmental disorders (F01-F99) / Anxiety, dissociative, stress-related, somatoform and other nonpsychotic mental disorders (F40-F48)
F43.9
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceReaction to severe stress, unspecified
A general category for emotional or behavioral reactions to severe stress that do not fit into more specific diagnostic categories.
CMS-HCC V28
N/A—
Not mapped
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
N/A—
Not mapped
ESRD/PACE
N/A—
Not mapped
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
Official- Trauma and stressor-related disorder, NOS
- Unspecified trauma and stressor-related disorder
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for F43.9 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for F43.9 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for F43.9 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for F43.9 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for F43.9 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for F43.9 in this effective period.
Buddy Documentation Tip
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is F43.9 an HCC code?
No. F43.9 is a billable ICD-10-CM code with no mapping under the CMS-HCC V28 or V24 community payment models, and none under the ESRD, Part D RxHCC, or HHS-HCC models.
- Code
- F43.9
- Description
- Reaction to severe stress, unspecified
- HCC (V28)
- No CMS-HCC V28 mapping
- RAF reference coefficient
- —
- Billable
- Yes
- Payment year
- 2026
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
F43.9 is the ICD-10-CM diagnosis code for reaction to severe stress, unspecified. A general category for emotional or behavioral reactions to severe stress that do not fit into more specific diagnostic categories. F43.9 sits in the ICD-10-CM chapter for mental, behavioral and neurodevelopmental disorders (f01-f99), within the section covering anxiety, dissociative, stress-related, somatoform and other nonpsychotic mental disorders (f40-f48).
F43.9 is a billable ICD-10-CM code, but the current payload does not show a mapping under the CMS-HCC V28 or V24 community payment models, and none under the ESRD, Part D RxHCC, or HHS-HCC models. Do not assign risk adjustment value from this page when no source-backed mapping is shown; verify the applicable model and payment year.
Use this code only when the specific type of stress reaction cannot be determined or documented.
HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for F43.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.