2027 ICD-10-CM Diagnosis Code R40.20Unspecified coma
ICD-10-CM Codes›R00–R99›R40-R46›R40
- Billable — Valid for Submission
- MCC — Major Complication or Comorbidity
- Risk Adjusts — HCC 202
- Not Chronic
R40.20 is a billable ICD-10-CM diagnosis code for unspecified coma. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 80 through 81, 791, 793. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 718 closely related codes. 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.
For Medicare Advantage risk adjustment, R40.20 maps to CMS-HCC Category 202 (Coma, Brain Compression/Anoxic Damage) under the V28 model, adding a risk factor of about 0.543 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
R40.20 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
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
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to R40.20: its own notes plus those printed at R40.2, R40, block R40-R46, and Chapter 18. A note printed at a category, block or chapter applies to every code under it.
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- Coma NOS
- Unconsciousness NOS
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
Code First
The underlying condition named in the note is sequenced before this code.
Notes
General instructions on how these codes are used.
- This chapter includes symptoms, signs, abnormal results of clinical or other investigative procedures, and ill-defined conditions regarding which no diagnosis classifiable elsewhere is recorded.
- Signs and symptoms that point rather definitely to a given diagnosis have been assigned to a category in other chapters of the classification. In general, categories in this chapter include the less well-defined conditions and symptoms that, without the necessary study of the case to establish a final diagnosis, point perhaps equally to two or more diseases or to two or more systems of the body. Practically all categories in the chapter could be designated 'not otherwise specified', 'unknown etiology' or 'transient'. The Alphabetical Index should be consulted to determine which symptoms and signs are to be allocated here and which to other chapters. The residual subcategories, numbered .8, are generally provided for other relevant symptoms that cannot be allocated elsewhere in the classification.
- The conditions and signs or symptoms included in categories R00-R94 consist of:
- (a) cases for which no more specific diagnosis can be made even after all the facts bearing on the case have been investigated;
- (b) signs or symptoms existing at the time of initial encounter that proved to be transient and whose causes could not be determined;
- (c) provisional diagnosis in a patient who failed to return for further investigation or care;
- (d) cases referred elsewhere for investigation or treatment before the diagnosis was made;
- (e) cases in which a more precise diagnosis was not available for any other reason;
- (f) certain symptoms, for which supplementary information is provided, that represent important problems in medical care in their own right.
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name R40.20, its category, or a range that includes it.
Excludes1 4
These codes carry an Excludes1 note naming R40.20: they are not reported together with it, unless the two conditions are unrelated.
- R40.0 Somnolencecoma (R40.2-) names R40.2-, which includes this code
- R40.1 Stuporcoma (R40.2-) names R40.2-, which includes this code
- R41.82 Altered mental status, unspecifiedaltered level of consciousness (R40.-) names R40.-, which includes this code
- R55 Syncope and collapseunconsciousness NOS (R40.2-) names R40.2-, which includes this code
Use Additional Code 2
These codes say to use an additional code from the note, and R40.20 is one of the codes named.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Coma R40.20
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
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.
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.
Code HistoryHistory
Questions About R40.20Overview
What is the ICD-10 code for unspecified coma?
The ICD-10-CM code for unspecified coma is R40.20 (sometimes written as R4020). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
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, 2026 through September 30, 2027.
What MS-DRG does R40.20 group to?
When unspecified coma is the principal diagnosis on an inpatient stay, it groups to MS-DRG 793, 791, 81, 80, with relative weights from 0.7941 to 4.2192 depending on complications. Higher weights mean higher Medicare reimbursement.
Is R40.20 a CC or MCC?
CMS lists R40.20 as an MCC (major complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 718 closely related codes in its exclusion list.
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 HCC is R40.20?
R40.20 (unspecified coma) maps to CMS-HCC Category 202 (Coma, Brain Compression/Anoxic Damage), commonly written as HCC 202, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 80 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. It does not map to any RxHCC in the Part D prescription drug model.
Does R40.20 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, R40.20 adds a risk adjustment factor of about 0.543 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.097 to 0.721 depending on the payment segment). A more severe related category (HCC 63, HCC 397, and HCC 398) supersedes it when both are reported. See the full factor table on the HCC 202 category page.
