Version 2024
Replaced Code
No Valid Principal Dx

2024 ICD-10-CM Diagnosis Code R40.20

Unspecified coma

ICD-10-CM Code:
ICD-10 Code for:
Unspecified coma
Is Billable?
Yes - Valid for Submission
Chronic Condition Indicator: [1]
Not chronic
Code Navigator:

Code Classification

  • Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified
    • Symptoms and signs involving cognition, perception, emotional state and behavior
      • Somnolence, stupor and coma

R40.20 is a billable diagnosis code used to specify a medical diagnosis of unspecified coma. The code is valid during the current fiscal year for the submission of HIPAA-covered transactions from October 01, 2023 through September 30, 2024.

Unspecified diagnosis codes like R40.20 are acceptable when clinical information is unknown or not available about a particular condition. Although a more specific code is preferable, unspecified codes should be used when such codes most accurately reflect what is known about a patient's condition. Specific diagnosis codes should not be used if not supported by the patient's medical record.

According to ICD-10-CM guidelines this code should not to be used as a principal diagnosis code when a related definitive diagnosis has been established.

Approximate Synonyms

The following clinical terms are approximate synonyms or lay terms that might be used to identify the correct diagnosis 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
  • Drug-induced coma
  • Hypothermic coma
  • Hypoxic-ischemic 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

Clinical Classification

Clinical Information

  • 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.

Replaced Code

This code was replaced in the 2024 ICD-10-CM code set with the code(s) listed below. The National Center for Health Statistics (NCHS) has published an update to the ICD-10-CM diagnosis codes which became effective October 1, 2023. This code was replaced for the FY 2024 (October 1, 2023 - September 30, 2024).

  • R40.2A - Nontraumatic coma due to underlying condition

Tabular List of Diseases and Injuries

The following annotation back-references are applicable to this diagnosis code. The Tabular List of Diseases and Injuries is a list of ICD-10-CM codes, organized "head to toe" into chapters and sections with coding notes and guidance for inclusions, exclusions, descriptions and more.

Inclusion Terms

Inclusion Terms
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.
  • Coma NOS
  • Unconsciousness NOS

Index to Diseases and Injuries References

The following annotation back-references for this diagnosis code are found in the injuries and diseases index. The Index to Diseases and Injuries is an alphabetical listing of medical terms, with each term mapped to one or more ICD-10-CM code(s).

Convert R40.20 to ICD-9-CM

  • ICD-9-CM Code: 780.01 - Coma
    Approximate Flag - The approximate mapping means there is not an exact match between the ICD-10 and ICD-9 codes and the mapped code is not a precise representation of the original code.

Patient Education


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.

A coma rarely lasts more than 2 to 4 weeks. The outcome for coma depends on the cause, severity, and site of the damage. People may come out of a coma with physical, intellectual, and psychological problems. Some people may remain in a coma for years or even decades. For those people, the most common cause of death is infection, such as pneumonia.

NIH: National Institute of Neurological Disorders and Stroke

[Learn More in MedlinePlus]

Code History

  • FY 2024 - No Change, effective from 10/1/2023 through 9/30/2024
  • FY 2023 - No Change, effective from 10/1/2022 through 9/30/2023
  • FY 2022 - No Change, effective from 10/1/2021 through 9/30/2022
  • FY 2021 - No Change, effective from 10/1/2020 through 9/30/2021
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
  • FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
  • FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017
  • FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016. This was the first year ICD-10-CM was implemented into the HIPAA code set.


[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.