R40.20Unspecified coma

R40.20 is the ICD-10-CM diagnosis code for unspecified coma. 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 R40.2, choose R40.20 (Unspecified coma) only when documentation doesn't support a more specific option: scale, eyes open (R40.21), scale, best verbal response (R40.22), scale, best motor response (R40.23), Glasgow coma scale, total score (R40.24) and nontraumatic coma due to underlying condition (R40.2A).

As a secondary diagnosis it is an MCC (major complication or comorbidity), which can move an inpatient stay into the highest-paying "with MCC" MS-DRG of its family, unless the principal diagnosis excludes it.

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), DRG 081 (Nontraumatic Stupor and Coma without MCC, relative weight 0.806), DRG 791 (Prematurity with Major Problems, relative weight 4.1075) and DRG 793 (Full Term Neonate with Major Problems, relative weight 4.2195), in MDC 01 (Diseases and Disorders of the Nervous System) and MDC 15 (Newborns and Other Neonates with Conditions Originating in the Perinatal Period), 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 780.01 (coma).