ICD-10-CM 2027
ICD-10 code for reaction stress
From the official ICD-10-CM alphabetic index entry “Stress › reaction”. Page updated September 29, 2026.
About coding reaction stress
The ICD-10-CM code for reaction stress is F43.9 (Reaction to severe stress, unspecified).
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.
Common questions about reaction stress ICD-10 codes
What is the ICD-10 code for reaction stress?
- F43.9 — Reaction to severe stress, unspecified.
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.