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ICD-10-CM 2027 diagnosis code

R40.0Somnolence

✓ Billable / specific

R40.0 is a valid, billable ICD-10-CM code for somnolence. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Looking up by condition? See ICD-10 code for Drowsiness, ICD-10 code for Somnolence.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About R40.0

R40.0 is the ICD-10-CM diagnosis code for Somnolence. It belongs to category R40 (Somnolence, stupor and coma), block R40-R46 (symptoms and signs involving cognition, perception, emotional state and behavior) and chapter 18 (symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within R40 (Somnolence, stupor and coma), R40.0 is specifically for Somnolence. Related codes cover stupor (R40.1), coma (R40.2), persistent vegetative state (R40.3) and transient alteration of awareness (R40.4).

Don't report R40.0 together with the conditions in its Excludes1 note: coma (R40.2-).

It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 080 (Nontraumatic Stupor and Coma with MCC, relative weight 1.7472) and DRG 081 (Nontraumatic Stupor and Coma without MCC, relative weight 0.806), in MDC 01 (Diseases and Disorders of the Nervous System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 780.09 (other alteration of consciousness).

Coding notes

Applicable toConditions and synonyms classified to this code
  • Drowsiness
Excludes1Not coded here — never report together with this code

Notes that apply from higher levels

Instructions written at a parent level also apply to R40.0.

› From R40 Somnolence, stupor and coma
Excludes1
  • neonatal coma (P91.5)
  • somnolence, stupor and coma in diabetes (E08-E13)
  • somnolence, stupor and coma in hepatic failure (K72.-)
  • somnolence, stupor and coma in hypoglycemia (nondiabetic) (E15)

Broader instructions also apply from R40-R46 Symptoms and signs involving cognition, perception, emotional state and behavior and Chapter 18: Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified.

Alphabetic index entries

2 entries

Terms in the official ICD-10-CM index that lead to R40.0.

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

ICD-9-CM equivalent

Converter →
  • 780.09Other alteration of consciousnessapproximate

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about R40.0

Is R40.0 billable?

Yes. R40.0 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can R40.0 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict R40.0 as a principal diagnosis.

Is R40.0 a CC or MCC?

No. R40.0 is neither a CC nor an MCC under MS-DRG v44.0.

What DRG does R40.0 group to?

R40.0 is used in the MS-DRG v44.0 logic for MS-DRG 080 (Nontraumatic Stupor and Coma with MCC) and MS-DRG 081 (Nontraumatic Stupor and Coma without MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for R40.0?

The CMS General Equivalence Mappings map R40.0 to ICD-9-CM 780.09.