2027 ICD-10-CM Diagnosis Code R40.0Somnolence
ICD-10-CM Codes›R00–R99›R40-R46›R40
- Billable — Valid for Submission
- Not Chronic
R40.0 is a billable ICD-10-CM diagnosis code for somnolence. 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. 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
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Daytime somnolence
- Disorder of excessive somnolence
- Drowsy
- Excessive daytime sleepiness
- Excessive somnolence
- Gets drowsiness
- Intermittent drowsiness
- Keeps falling asleep
- Neonatal drowsiness
- Neonatal encephalopathy
- Post-ictal drowsiness
- Post-ictal state
- Somnolence syndrome
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to R40.0: its own notes plus those printed at 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.
- Drowsiness
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
- coma (R40.2-)
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.
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 R40.0, its category, or a range that includes it.
Excludes1 1
These codes carry an Excludes1 note naming R40.0: they are not reported together with it, unless the two conditions are unrelated.
Use Additional Code 2
These codes say to use an additional code from the note, and R40.0 is one of the codes named.
Index to Diseases and InjuriesGuidance
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Sleepiness
compelling urge to sleep.
Patient EducationClinical
Sleep Disorders
While you are sleeping your brain and body functions are still active. Sleep is a natural process that helps your body restore energy, supports learning and memory, and keeps you healthy.
The full article covers:
- What is sleep?
- What are sleep disorders?
- What causes sleep disorders?
- What are the symptoms of sleep disorders?
- How are sleep disorders diagnosed?
- What are the treatments for sleep disorders?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert R40.0 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About R40.0Overview
What is the ICD-10 code for somnolence?
The ICD-10-CM code for somnolence is R40.0 (sometimes written as R400). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is R40.0 (Somnolence, stupor and coma) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report somnolence on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does R40.0 group to?
When somnolence is the principal diagnosis on an inpatient stay, it groups to MS-DRG 81, 80, with relative weights from 0.7941 to 1.7476 depending on complications. Higher weights mean higher Medicare reimbursement.
Can R40.0 be a principal diagnosis?
Use it with care. This is a symptom code, so once a definitive diagnosis explaining the somnolence is established, that condition takes the principal position instead.
Can R40.0 be reported with a code from R40.2?
Not as a rule. The Excludes1 note on R40.0 lists "coma (R40.2-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
