R40.2A Nontraumatic coma due to underlying condition

Billable ICD-10-CM code, FY2026. Acts as a Major Complication or Comorbidity (MCC) as a secondary diagnosis.

Applicable to

• Secondary coma

Excludes1 (never code together)

• coma scale, best motor response (R40.24.-)
• coma scale, best verbal response (R40.22.-)
• coma scale, eyes open (R40.21.-)
• Glasgow coma scale, total score (R40.23.-)

Code first

• underlying condition

Applies from R40 Somnolence, stupor and coma

Excludes1 (never code together)

• 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)

Applies from R40.2 Coma

Code first

• any associated:
• fracture of skull (S02.-)
• intracranial injury (S06.-)

Notes

• One code from each subcategory, R40.21-R40.23, is required to complete the coma scale

Risk adjustment (HCC)

• CMS-HCC V28: HCC 202 — Coma, Brain Compression/Anoxic Damage
• CMS-HCC V22: HCC 80 — Coma, Brain Compression/Anoxic Damage
• ESRD V24: HCC 80

MS-DRG index

Defines the logic of DRG(s) 080-081 in MDC 01.

Medicare Code Edits (MCE v43.1 (April 2026))

• Unacceptable principal diagnosis: These codes describe a circumstance which influences care but is not a current illness or injury, or capture only an underlying condition, and are unacceptable as principal diagnosis.

Code annotations containing back-references to R40.2A

Back-references to R40.2

• Type 1 Excludes: R40.0 Somnolence ("coma (R40.2-)")
• Type 1 Excludes: R40.1 Stupor ("coma (R40.2-)")
• Type 1 Excludes: R55 Syncope and collapse ("unconsciousness NOS (R40.2-)")

Back-references to R40

• Type 1 Excludes: R41.82 Altered mental status, unspecified ("altered level of consciousness (R40.-)")
• Use Additional: T67.0 Heatstroke and sunstroke ("coma and stupor (R40.-)")

Diagnosis Index entries for R40.2A

• Coma › nontraumatic, due to underlying condition
• Coma › secondary

Nearby codes

• R40.2440 Other coma, without documented Glasgow coma scale score, or with partial score reported, unspecified time
• R40.2441 Other coma, without documented Glasgow coma scale score, or with partial score reported, in the field [EMT or ambulance]
• R40.2442 Other coma, without documented Glasgow coma scale score, or with partial score reported, at arrival to emergency department
• R40.2443 Other coma, without documented Glasgow coma scale score, or with partial score reported, at hospital admission
• R40.2444 Other coma, without documented Glasgow coma scale score, or with partial score reported, 24 hours or more after hospital admission
• R40.2A Nontraumatic coma due to underlying condition (this code)
• R40.3 Persistent vegetative state
• R40.4 Transient alteration of awareness