2026 ICD-10-CM Diagnosis Code R40.20Unspecified coma

ICD-10-CM Codes›R00–R99›R40-R46›R40

ICD-10-CM R40.20
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

R40.20 is a billable ICD-10-CM diagnosis code for unspecified coma. 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Coma; stupor; and brain damage.

Code Identity

ICD-10-CM Code
R40.20
Billable Status
Yes — Valid for Submission
Code Describes
Unspecified coma
Short Description
Unspecified coma
Same as the full description in the CMS dataset.
Parent Code
R40.2
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 CodeR40.20Unspecified coma

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Alcoholic coma
  • Blistering of skin due to drug-induced coma
  • Coma
  • Coma due to malnutrition-related diabetes mellitus
  • Disorder due to malnutrition related diabetes mellitus
  • Disorder of nervous system due to malnutrition related diabetes mellitus
  • Drug-induced coma
  • Hypothermic coma
  • Hypoxic-ischemic coma
  • Irreversible coma
  • Ischemic stroke with coma
  • Monocular movements in coma
  • Pituitary coma
  • Post-anoxic coma
  • Post-cardiorespiratory arrest coma
  • Post-ictal coma
  • Post-traumatic coma
  • Spontaneous eye movements in coma
  • Unconscious
  • Unresponsive
  • Uremic coma
  • Uremic encephalopathy

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Coma NOS
  • Unconsciousness NOS

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.

    • Coma

Clinical ClassificationClinical

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

CCSR NVS013
Coma; stupor; and brain damage
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Akinetic Mutism

    a syndrome characterized by a silent and inert state without voluntary motor activity despite preserved sensorimotor pathways and vigilance. bilateral frontal lobe dysfunction involving the anterior cingulate gyrus and related brain injuries are associated with this condition. this may result in impaired abilities to communicate and initiate motor activities. (from adams et al., principles of neurology, 6th ed, p348; fortschr neurol psychiatr 1995 feb;63(2):59-67)

  • Brain Death

    a state of prolonged irreversible cessation of all brain activity, including lower brain stem function with the complete absence of voluntary movements, responses to stimuli, brain stem reflexes, and spontaneous respirations. reversible conditions which mimic this clinical state (e.g., sedative overdose, hypothermia, etc.) are excluded prior to making the determination of brain death. (from adams et al., principles of neurology, 6th ed, pp348-9)

  • Coma

    a profound state of unconsciousness associated with depressed cerebral activity from which the individual cannot be aroused. coma generally occurs when there is dysfunction or injury involving both cerebral hemispheres or the brain stem reticular formation.

  • Coma, Post-Head Injury

    prolonged unconsciousness from which the individual cannot be aroused, associated with traumatic injuries to the brain. this may be defined as unconsciousness persisting for 6 hours or longer. coma results from injury to both cerebral hemispheres or the reticular formation of the brain stem. contributing mechanisms include diffuse axonal injury and brain edema. (from j neurotrauma 1997 oct;14(10):699-713)

  • Comamonadaceae

    a family of gram-negative aerobic bacteria in the order burkholderiales, encompassing the acidovorans rrna complex. some species are pathogenic to plants.

  • Comamonas

    a genus of gram-negative, straight or slightly curved rods which are motile by polar flagella and which accumulate poly-beta-hydroxybutyrate within the cells.

  • Comamonas testosteroni

    a species of gram-negative, aerobic rods formerly called pseudomonas testosteroni. it is differentiated from other comamonas species by its ability to assimilate testosterone and to utilize phenylacetate or maleate as carbon sources.

  • Convulsive Therapy

    convulsions induced in order to treat mental disorders. it is used primarily in the treatment of severe affective disorders and schizophrenia.

  • Delftia acidovorans

    a species of gram-negative rod-shaped bacteria found ubiquitously and formerly called comamonas acidovorans and pseudomonas acidovorans. it is the type species of the genus delftia.

  • Diabetic Coma

    a state of unconsciousness as a complication of diabetes mellitus. it occurs in cases of extreme hyperglycemia or extreme hypoglycemia as a complication of insulin therapy.

  • Glasgow Coma Scale

    a scale that assesses the response to stimuli in patients with craniocerebral injuries. the parameters are eye opening, motor response, and verbal response.

  • Hepatic Encephalopathy

    a syndrome characterized by central nervous system dysfunction in association with liver failure, including portal-systemic shunts. clinical features include lethargy and confusion (frequently progressing to coma); asterixis; nystagmus, pathologic; brisk oculovestibular reflexes; decorticate and decerebrate posturing; muscle spasticity; and bilateral extensor plantar reflexes (see reflex, babinski). electroencephalography may demonstrate triphasic waves. (from adams et al., principles of neurology, 6th ed, pp1117-20; plum & posner, diagnosis of stupor and coma, 3rd ed, p222-5)

  • Hyperglycemic Hyperosmolar Nonketotic Coma

    a serious complication of type 2 diabetes mellitus. it is characterized by extreme hyperglycemia; dehydration; serum hyperosmolarity; and depressed consciousness leading to coma in the absence of ketosis and acidosis.

  • Insulin Coma

    severe hypoglycemia induced by a large dose of exogenous insulin resulting in a coma or profound state of unconsciousness from which the individual cannot be aroused.

  • Santalaceae

    a plant family of the order santalales, subclass rosidae, class magnoliopsida. they are parasites that form connections (haustoria) to their hosts to obtain water and nutrients. the one-seeded fruit may be surrounded by a brightly colored nut-like structure.

  • Frontal Lobe

    the part of the cerebral hemisphere anterior to the central sulcus, and anterior and superior to the lateral sulcus.

  • Reticular Formation

    a region extending from the pons & medulla oblongata through the mesencephalon, characterized by a diversity of neurons of various sizes and shapes, arranged in different aggregations and enmeshed in a complicated fiber network.

  • Delftia

    a genus of gram-negative, strictly aerobic chemoorganotrophic bacteria, in the family comamonadaceae.

Patient EducationClinical

Coma

A coma is a deep state of unconsciousness. An individual in a coma is alive but unable to move or respond to his or her environment. Coma may occur as a complication of an underlying illness, or as a result of injuries, such as brain injury.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert R40.20 to ICD-9-CMHistory

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

ICD-9-CM
780.01 Coma
Approximate The match is approximate rather than exact.

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 R40.20Overview

Is R40.20 (Coma) a billable code?

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

Can R40.20 be a principal diagnosis?

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

What is the ICD-9 equivalent of R40.20?

Under the General Equivalence Mappings, unspecified coma converts to ICD-9-CM 780.01 (coma). The mapping is approximate, so confirm the match fits the documentation.

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.