2026 ICD-10-CM Diagnosis Code F05Delirium due to known physiological condition
ICD-10-CM Codes›F01–F99›F01-F09›F05
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Not a Principal Diagnosis
- Not Chronic
F05 is a billable ICD-10-CM diagnosis code for delirium due to known physiological condition. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 880. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 1 closely related codes. The code is not accepted as a principal diagnosis by the Medicare Code Editor. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Neurocognitive disorders.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for F05.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Acute confusional state, of endocrine origin
- Acute confusional state, of infective origin
- Acute confusional state, of metabolic origin
- Acute confusional state, post-traumatic
- Delirium due to hepatic encephalopathy
- Delirium of mixed origin
- Hyperactive behavior
- Hyperactive postoperative delirium
- Hypoactive postoperative delirium
- Mixed hyperactive hypoactive postoperative delirium
- Post-injection delirium sedation syndrome
- Postoperative confusion
- Postoperative delirium
- Postseizure confusion
- Postseizure delirium
- Senile dementia with delirium
- Sundowning
- Toxic confusional state
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Inclusion Terms
- 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
Code First
- the underlying physiological condition, such as:
- dementia F03.9
Type 1 Excludes
- delirium NOS R41.0
Type 2 Excludes
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
Certain conditions have both an underlying etiology and multiple body system manifestations due to the underlying etiology. For such conditions, the ICD-10-CM has a coding convention that requires the underlying condition be sequenced first followed by the manifestation. Wherever such a combination exists, there is a "use additional code" note at the etiology code, and a "code first" note at the manifestation code. These instructional notes indicate the proper sequencing order of the codes, etiology followed by manifestation.
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
A type 2 excludes note represents "Not included here". An excludes2 note indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Delirium, delirious (acute or subacute) (not alcohol- or drug-induced) R41.0
Dementia (degenerative (primary)) (persisting) (unspecified severity) (without behavioral disturbance, psychotic disturbance, mood disturbance, and anxiety) F03.90
Epilepsy, epileptic, epilepsia (attack) (cerebral) (convulsion) (fit) (seizure) G40.909
twilight F05
Insanity, insane See Also: Psychosis;
Senile, senility See Also: condition; R41.81
epileptic F05
Sundowning F05
Syndrome See Also: Disease;
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
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.
The full article covers:
- What is delirium?
- What causes delirium?
- Who is more likely to get delirium?
- What are the symptoms of delirium?
- How is delirium diagnosed?
- What are the treatments for delirium?
- Can delirium be prevented?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert F05 to ICD-9-CMHistory
Code HistoryHistory
Questions About F05Overview
What is the ICD-10 code for delirium due to known physiological condition?
The ICD-10-CM code for delirium due to known physiological condition is F05. It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is F05 (Delirium due to known physiological condition) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report delirium due to known physiological condition on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does F05 group to?
On inpatient claims, delirium due to known physiological condition maps to MS-DRG 880 (acute Adjustment Reaction and Psychosocial Dysfunction), which carries a relative weight of 0.9602. Higher weights mean higher Medicare reimbursement.
Is F05 a CC or MCC?
CMS lists F05 as a CC (complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 1 closely related codes in its exclusion list.
Can F05 be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because delirium due to known physiological condition describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.
