2026 ICD-10-CM Diagnosis Code R40.2421Glasgow coma scale score 9-12, in the field [EMT or ambulance]

ICD-10-CM Codes›R00–R99›R40-R46›R40

ICD-10-CM R40.2421
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

R40.2421 is a billable ICD-10-CM diagnosis code for Glasgow coma scale score 9-12, in the field [EMT or ambulance]. The 7th character 1 reports a Glasgow coma scale score recorded in the field by EMT or ambulance personnel. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). The code is not accepted as a principal diagnosis by the Medicare Code Editor. 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 Nervous system signs and symptoms.

Code Identity

ICD-10-CM Code
R40.2421
Billable Status
Yes — Valid for Submission
Code Describes
Glasgow coma scale score 9-12, in the field [EMT or ambulance]
Short Description
Glasgow coma scale score 9-12, in the field
Parent Code
R40.242
Glasgow coma scale score 9-12

Code Classification

ChapterR00–R99Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified
SectionR40-R46Symptoms and signs involving cognition, perception, emotional state and behavior
CategoryR40Somnolence, stupor and coma
This CodeR40.2421Glasgow coma scale score 9-12, in the field [EMT or ambulance]

Code EditsBilling

Medicare Code Editor checks that affect claim validity for R40.2421.

Unacceptable principal diagnosis
There are selected codes that describe a circumstance which influences an individual's health status but not a current illness or injury, or codes that are not specific manifestations but may be due to an underlying cause. These codes are considered unacceptable as a principal diagnosis.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR SYM010
Nervous system signs and symptoms
Default principal diagnosis: inpatient No · outpatient No

Convert R40.2421 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
No Map There is no ICD-9 equivalent for this code.

Code History & ChangesHistory

Replacement R40.2421 replaces the following previously assigned code(s):

  • R40.242 - Glasgow coma scale score 9-12
FY 2018AddedAdded to the ICD-10-CM code setEffective October 1, 2017.
FY 2019–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About R40.2421Overview

Is R40.2421 (Glasgow coma scale score 9-12) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report Glasgow coma scale score 9-12, in the field [EMT or ambulance] on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character 1 in R40.2421 mean?

The final character 1 reports a Glasgow coma scale score recorded in the field by EMT or ambulance personnel, in this case involving the Glasgow coma scale score 9-12.

Can R40.2421 be a principal diagnosis?

No. The Medicare Code Editor rejects this code as a principal diagnosis because Glasgow coma scale score 9-12, in the field [EMT or ambulance] describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.