MCMCB Pro
R40.2A

R40.2ANontraumatic coma due to underlying condition

Billable / specific codeICD-10-CM

R40.2A is a billable, specific ICD-10-CM code for nontraumatic coma due to underlying condition. It is valid for submission on a claim.

Excludes1 — never code together

These conditions cannot occur together. Billing both on the same encounter is a denial.

  • 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

The underlying condition must be sequenced before this code.

  • underlying condition

Inclusion terms

Alternative wordings a physician may use in the chart for this same code.

  • Secondary coma

Risk adjustment

R40.2A risk-adjusts. Under the CMS-HCC V28 model it maps to this category:

  • HCC 202 Coma, Brain Compression/Anoxic Damage0.543 RAF

Coefficient shown for the Community Non-dual Aged segment. A higher HCC in the same hierarchy will suppress this one, so capturing it does not always add score.

Medicare coverage

R40.2A is named in 18 Medicare coverage policies 18 listing it as supporting medical necessity. Which of them applies to you depends on your Medicare contractor, and coverage genuinely differs by state.

  • A54799Billing and Coding: Urine Drug Testing
  • A55001Billing and Coding: Urine Drug Testing
  • A56612Billing and Coding: CT of the Head
  • A56625Billing and Coding: Echocardiography

How R40.2A is indexed

Coders do not find codes by browsing the tabular list — they look them up in the alphabetic index, under the word the physician wrote. These are the index entries that lead here, so you can see which chart wordings map to R40.2A.

  • Comanontraumatic, due to underlying condition
  • Comasecondary

Related codes at this level

Codes that share R40.2. If R40.2A is not quite right, the correct code is usually one of these.

Questions about R40.2A

Is R40.2A a billable ICD-10-CM code?
Yes. R40.2A is a billable, specific ICD-10-CM code and is valid for submission on a claim.
Where does R40.2A sit in the tabular list?
Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R99), in the block Symptoms and signs involving cognition, perception, emotional state and behavior (R40-R46).
What cannot be coded together with R40.2A?
R40.2A carries an Excludes1 note, which means the conditions it lists can never be coded together with it on the same encounter.
ICD-10-CMFY2026-Apr· effective April 1, 2026

Loaded directly from the CMS/NCHS ICD-10-CM public-domain release — see data sources and our editorial policy. If this page disagrees with the CMS tabular list, this page is wrong. Reference information for professional coders; not medical or billing advice.