Alphabetic Index FY2027

F05

Delirium due to known physiological condition

FY2027Chapter 5: Mental, Behavioral and Neurodevelopmental disorders/F01–F09 Mental disorders due to known physiological conditions

BillableComplete code, valid to report
Care settingsHospice: not accepted as primaryHospital CCIPF Primary · MS-DRG 880

F05 is a billable ICD-10-CM diagnosis code for delirium due to known physiological condition. It is part of the FY2027 code set, effective October 1, 2026. The Alphabetic Index lists it under 26 entries. Its coding notes include a Code first instruction, 1 Excludes1 entry and 2 Excludes2 entries.

Code first

If the underlying condition listed here is present and known, sequence it first.

This code
  • the underlying physiological condition, such as:

Excludes1

Not coded here. The listed conditions generally should not be reported together.

This code

Excludes2

Not included here. Both codes may be reported if the patient has both conditions.

This code
Also from chapter/block level (1 note)
Inherited from Chapter 5 Mental, Behavioral and Neurodevelopmental disorders
  • symptoms, signs and abnormal clinical laboratory findings, not elsewhere classified (R00-R99)

Care settings

How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.

Hospice: not accepted as primary

Not accepted as the principal diagnosis on a hospice claim (bill types 081x and 082x). The Integrated OCE returns an edit for this code.
Reason: Supplementary or additional code, not allowed as principal diagnosis.

Source: CMS Integrated Outpatient Code Editor (IOCE) v27.3, effective October 1, 2026, edit 113

Hospital CC

Counts as a complication or comorbidity (CC) when reported as a secondary diagnosis on an inpatient claim. It does not count when the principal diagnosis is one of the 1 code in its exclusion list. Some MS-DRGs also ignore a CC or MCC that defines the DRG.

Source: CMS MS-DRG Definitions Manual v44, effective October 1, 2026, Appendix C

IPF Primary

IPF MS-DRG adjustment. A principal diagnosis of this code groups to this MS-DRG:

MS-DRGDescriptionFactor
880Acute adjustment reaction & psychosocial dysfunction1.08
A principal diagnosis that groups to none of the 19 designated MS-DRGs gets no MS-DRG adjustment. Otherwise the claim still receives the federal per diem base rate and the other adjustments. This code carries a Code first note (see the Code first note). Under CMS’s IPF grouper rules, when a psychiatric code carries a Code first note, the provider follows the instructions in the Tabular List, and the grouper identifies the principal diagnosis as non-psychiatric and searches the secondary codes for a psychiatric code.

Source: CMS IPF PPS FY 2027 final rule (CMS-1847-F), Addendum A; code lists from the CMS MS-DRG Definitions Manual v44, Addendum B-2 (Code First table); effective for discharges on or after October 1, 2026

Includes

Further defines or gives examples of the content of the category.

Also from chapter/block level (1 note)
Inherited from Chapter 5 Mental, Behavioral and Neurodevelopmental disorders
  • disorders of psychological development

Inclusion terms

Conditions classified to this code.

This code
  • Acute or subacute brain syndrome
  • Acute or subacute confusional state (nonalcoholic)
  • Acute or subacute infective psychosis
  • Acute or subacute organic reaction
  • Acute or subacute psycho-organic syndrome
  • Delirium of mixed etiology
  • Delirium superimposed on dementia
  • Sundowning

Notes

Also from chapter/block level (1 note)
Inherited from F01–F09 Mental disorders due to known physiological conditions
  • This block comprises a range of mental disorders grouped together on the basis of their having in common a demonstrable etiology in cerebral disease, brain injury, or other insult leading to cerebral dysfunction. The dysfunction may be primary, as in diseases, injuries, and insults that affect the brain directly and selectively; or secondary, as in systemic diseases and disorders that attack the brain only as one of the multiple organs or systems of the body that are involved.

Alphabetic Index terms

Terms the official Alphabetic Index lists for this code. 26 entries

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