F05 — Delirium due to known physiological condition
Is F05 billable?
Yes — F05 is billable for FY2027. F05 is a valid, billable ICD-10-CM code at the highest level of specificity in its branch. F05 may be submitted for encounters from October 1, 2026 through September 30, 2027.
F05 at a glance
| Code | F05 |
|---|---|
| Description | Delirium due to known physiological condition |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
What Medicare edits apply to F05?
The Medicare Code Editor screens inpatient claims before they are grouped. These edits name F05 directly.
CMS will reject this code as the principal diagnosis on an inpatient claim. It describes something other than the condition chiefly responsible for the admission.
Which MS-DRGs does F05 group to?
F05 sits in MDC 19 and helps define the logic of 1 MS-DRG (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 880Acute Adjustment Reaction and Psychosocial Dysfunctionmedical
As a secondary diagnosis, F05 is a complication or comorbidity (CC), which can move a stay into a higher-paying DRG.
How is F05 listed in the Alphabetic Index?
These are the routes through the Alphabetic Index that lead to F05. They show the wording a clinician may have documented, which often differs from the Tabular description.
- Sundowning
- Confusion, confused › epileptic
- Delirium, delirious › postprocedural (acute or subacute) (not alcohol- or drug-induced)
- Delirium, delirious › puerperal (acute or subacute) (not alcohol- or drug-induced)
- Epilepsy, epileptic, epilepsia › twilight (attack) (cerebral) (convulsion) (fit) (seizure)
- Psychosis, psychotic › infective
- Puerperal, puerperium › delirium NEC (complicated by, complications)
- Twilight state › epileptic
- Confusion, confused › acute › with dementia
- Delirium, delirious › with › dementia (acute or subacute) (not alcohol- or drug-induced)
- Delirium, delirious › due to › general medical condition (acute or subacute) (not alcohol- or drug-induced)
- Delirium, delirious › due to › multiple etiologies (acute or subacute) (not alcohol- or drug-induced)
Excludes1 — never code together
The conditions below can never be reported together with F05 on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
- delirium NOS (R41.0)
Code first
The underlying condition below must be sequenced before F05. F05 describes a manifestation and cannot be the principal or first-listed diagnosis.
- the underlying physiological condition, such as:
- dementia (F03.9-)
Excludes2 — not included here
The conditions below are not part of F05, but a patient may have both at the same time. When documentation supports it, F05 and the excluded code may both be reported.
Inclusion terms
Alternative wording in documentation that is classified to F05.
- 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
Excludes2 — not included here — inherited from Chapter 5
The conditions below are not part of F05, but a patient may have both at the same time. When documentation supports it, F05 and the excluded code may both be reported.
- symptoms, signs and abnormal clinical laboratory findings, not elsewhere classified (R00-R99)
How long has F05 existed?
F05 has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.
Which codes are confused with F05?
ICD-10-CM declares these codes mutually exclusive with F05 — exactly one of each pair can be correct for a given encounter.