ICD-10-CM 2027
ICD-10 code for stress severe reaction
From the official ICD-10-CM alphabetic index entry “Reaction › stress (severe)”. Page updated September 29, 2026.
About coding stress severe reaction
The ICD-10-CM code for stress severe reaction is F43.9 (Reaction to severe stress, unspecified). The official index lists 2 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on F43.9.
Within F43, choose F43.9 (Reaction to severe stress, unspecified) only when documentation doesn't support a more specific option: acute stress reaction (F43.0), post-traumatic stress disorder (PTSD) (F43.1), adjustment disorders (F43.2) and other reactions to severe stress (F43.8).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 882 (Neuroses Except Depressive, relative weight 0.9952), in MDC 19 (Mental Diseases and Disorders), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
More specific stress severe reaction codes (official index)
Common questions about stress severe reaction ICD-10 codes
What is the ICD-10 code for stress severe reaction?
- F43.9 — Reaction to severe stress, unspecified. More specific codes apply when the documentation supports them: F43.0, F43.89.
What is the ICD-10 code for acute stress severe reaction?
- F43.0 — Acute stress reaction.
Is F43.9 billable?
- Yes. F43.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can F43.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict F43.9 as a principal diagnosis.
Is F43.9 a CC or MCC?
- No. F43.9 is neither a CC nor an MCC under MS-DRG v44.0.