All ICD10 Codes
F05Billable, valid for claims from October 1, 2026

Delirium due to known physiological condition

In Mental disorders due to known physiological conditions (F01-F09), chapter 5: Mental, Behavioral and Neurodevelopmental Disorders

  • F05 is billable and valid on claims for FY 2027. If the record has more detail, check the other codes under F01-F09 below.
  • As a secondary diagnosis it is a CC (complication or comorbidity), which can raise the MS-DRG payment. It doesn't count when the principal diagnosis is one of 1 closely related codes.
  • Doesn't count toward a Medicare Advantage risk score (no HCC in V28).
  • AHRQ's Chronic Condition Indicator classes it as not chronic (an acute or short-term condition).
  • More than 934 US deaths in 2024 had an underlying cause in category F05, per the National Vital Statistics System on CDC WONDER. Death records use WHO ICD-10, so the count is for the whole category.
  • Medicare edits don't accept it as the principal diagnosis. (Unacceptable Principal list)

Also indexed as: Confusion, acute, with dementia; Confusion, epileptic; Delirium, with, dementia; Delirium, due to, general medical condition; Delirium, due to, multiple etiologies; Delirium, postprocedural; Delirium, puerperal; Dementia), with, acute confusional state; Epilepsy, twilight; Insanity, confusional, acute or subacute; Psychosis, confusional, acute or subacute; Psychosis, infective; Psychosis, organic, due to or associated with, disease, endocrine or metabolic, acute or subacute; Psychosis, organic, due to or associated with, epilepsy transient; Psychosis, organic, due to or associated with, infection, brain, acute or subacute; Psychosis, organic, due to or associated with, trauma, brain, acute or subacute; Psychosis, organic, infective, acute or subacute; Psychosis, organic, post-traumatic, acute or subacute; Puerperal, delirium NEC; Senile, with, acute confusional state; State, confusional, acute, with, senility or dementia; State, confusional, epileptic; State, twilight, epileptic; Sundowning; Syndrome, psycho-organic, acute or subacute; Twilight state, epileptic

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Instructional notes

Includes: conditions that are coded here

  • 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

Excludes1: not coded here, use a different code

Excludes2: not included here, code separately if applicable

Code first: code the underlying condition first, then this code

  • the underlying physiological condition, such as:
  • dementia (F03.9-)

Official coding guidelines

From the ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027 (CMS and NCHS). Links open the PDF at the right page.

Covers psychological pain disorders, substance use, abuse, dependence and remission, factitious disorder including Munchausen by proxy, and dementia severity.

Read Section I.C.5 (page 43)

Other codes under F01-F09

Mental disorders due to known physiological conditions (F01-F09)

F05 MS-DRG

As the principal diagnosis, F05 groups to MS-DRG 880 (v44.0).

Related conditions

Grouped by AHRQ's Clinical Classifications Software Refined (CCSR), which sorts every diagnosis code into clinically meaningful categories.

F05 is in Neurocognitive disorders (NVS011, its default category), with 95 codes. Others in it:

  • F01.50 Vascular dementia, unspecified severity, without behavioral disturbance, psychotic disturbance, mood disturbance, and anxiety
  • F01.511 Vascular dementia, unspecified severity, with agitation
  • F01.518 Vascular dementia, unspecified severity, with other behavioral disturbance
  • F01.52 Vascular dementia, unspecified severity, with psychotic disturbance
  • F01.53 Vascular dementia, unspecified severity, with mood disturbance
  • F01.54 Vascular dementia, unspecified severity, with anxiety
  • F01.A0 Vascular dementia, mild, without behavioral disturbance, psychotic disturbance, mood disturbance, and anxiety
  • F01.A11 Vascular dementia, mild, with agitation

Medicare coverage articles listing F05

These 17 Medicare billing and coding articles list F05 as a diagnosis that supports medical necessity for the services they cover. From the CMS Medicare Coverage Database; check your own contractor's article before billing.

And 7 more.

Other codes that refer to F05

Notes on these codes point to F05.

  • F03 Excludes2: dementia with delirium or acute confusional state (F05)
  • F06 Excludes2: delirium due to known physiological condition (F05)
  • G30 Use Additional Code: delirium, if applicable (F05)
  • R41.0 Excludes1: delirium due to known physiological condition (F05)
  • T81.89 Use Additional Code: postprocedural delirium (F05)

About the condition

Plain-language background from MedlinePlus (National Library of Medicine), not coding guidance.

Delirium

Delirium is a mental state in which you are confused, disoriented, and not able to think or remember clearly. It usually starts suddenly. It is often temporary and treatable.

Read more about delirium on MedlinePlus

Code history

Valid since FY2016, when ICD-10-CM took effect on October 1, 2015. No changes since.

ICD-9-CM equivalent

Legacy crosswalk from the CMS General Equivalence Mappings (last updated 2018).

  • 293.0 Delirium due to conditions classified elsewhere (approximate)
  • 293.1 Subacute delirium (approximate)
ICD-9 to ICD-10 converter