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ICD-10-CM 2027 diagnosis code

F43.9Reaction to severe stress, unspecified

✓ Billable / specific

F43.9 is a valid, billable ICD-10-CM code for reaction to severe stress, unspecified. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Looking up by condition? See ICD-10 code for Stress, ICD-10 code for Stress disorder, ICD-10 code for Stress severe reaction.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About F43.9

F43.9 is the ICD-10-CM diagnosis code for reaction to severe stress, unspecified. It belongs to category F43 (reaction to severe stress, and adjustment disorders), block F40-F48 (anxiety, dissociative, stress-related, somatoform and other nonpsychotic mental disorders) and chapter 5 (mental, Behavioral and Neurodevelopmental disorders). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

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.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 309.9 (unspecified adjustment reaction).

Coding notes

Applicable toConditions and synonyms classified to this code
  • Trauma and stressor-related disorder, NOS
  • Unspecified trauma and stressor-related disorder

Notes that apply from higher levels

Instructions written at a parent level also apply to F43.9.

Broader instructions also apply from Chapter 5: Mental, Behavioral and Neurodevelopmental disorders.

Alphabetic index entries

6 entries

Terms in the official ICD-10-CM index that lead to F43.9.

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

MDC 19 · Mental Diseases and Disorders

ICD-9-CM equivalent

Converter →
  • 309.9Unspecified adjustment reactionapproximate

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about F43.9

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.

What DRG does F43.9 group to?

F43.9 is used in the MS-DRG v44.0 logic for MS-DRG 882 (Neuroses Except Depressive). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for F43.9?

The CMS General Equivalence Mappings map F43.9 to ICD-9-CM 309.9.