2026 ICD-10-CM Diagnosis Code R40.4Transient alteration of awareness

ICD-10-CM Codes›R00–R99›R40-R46›R40

ICD-10-CM R40.4
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

R40.4 is a billable ICD-10-CM diagnosis code for transient alteration of awareness. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). As a symptom code, it should not be used as a principal diagnosis once a related definitive diagnosis has been established. Coders also document this condition as decreased level of consciousness. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Nervous system signs and symptoms.

Code Identity

ICD-10-CM Code
R40.4
Billable Status
Yes — Valid for Submission
Code Describes
Transient alteration of awareness
Short Description
Transient alteration of awareness
Same as the full description in the CMS dataset.
Parent Code
R40
Somnolence, stupor and coma

Code Classification

ChapterR00–R99Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified
SectionR40-R46Symptoms and signs involving cognition, perception, emotional state and behavior
CategoryR40Somnolence, stupor and coma
This CodeR40.4Transient alteration of awareness

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Decreased level of consciousness
  • Feeling faint
  • Fluctuating level of consciousness
  • Transient alteration of awareness

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Alteration(of), Altered
      • awareness
        • transient

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR SYM010
Nervous system signs and symptoms
Default principal diagnosis: inpatient Yes · outpatient Yes

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 R40.4 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
780.02 Trans alter awareness
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About R40.4Overview

Is R40.4 (Somnolence, stupor and coma) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report transient alteration of awareness on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Can R40.4 be a principal diagnosis?

Use it with care. This is a symptom code, so once a definitive diagnosis explaining the transient alteration of awareness is established, that condition takes the principal position instead.

What is the ICD-9 equivalent of R40.4?

Under the General Equivalence Mappings, transient alteration of awareness converts to ICD-9-CM 780.02 (trans alter awareness). The mapping is a direct match.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.