2027 ICD-10-CM Diagnosis Code G92.9Unspecified toxic encephalopathy

ICD-10-CM Codes›G00–G99›G89-G99›G92

ICD-10-CM G92.9
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

G92.9 is a billable ICD-10-CM diagnosis code for unspecified toxic encephalopathy. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 23 through 24, 91 through 93, 791, 793. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 47 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Drug induced or toxic related condition and Other nervous system disorders (neither hereditary nor degenerative).

Code Identity

ICD-10-CM Code
G92.9
Billable Status
Yes — Valid for Submission
Code Describes
Unspecified toxic encephalopathy
Short Description
Unspecified toxic encephalopathy
Same as the full description in the CMS dataset.
Parent Code
G92
Toxic encephalopathy

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG89-G99Other disorders of the nervous system
CategoryG92Toxic encephalopathy
This CodeG92.9Unspecified toxic encephalopathy

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Ammonia encephalopathy
  • Arsenic encephalopathy
  • Carbon monoxide encephalopathy
  • Drug-induced encephalopathy
  • Encephalopathy caused by heavy metal
  • Inflammation of spinal cord caused by toxin
  • Lead and/or lead compound poisoning
  • Organic mercury poisoning
  • Organophosphate encephalopathy
  • Poisoning caused by mercury
  • Toxic encephalopathy
  • Toxic encephalopathy caused by carbon tetrachloride
  • Toxic encephalopathy caused by hydroxyquinoline
  • Toxic encephalopathy caused by lead
  • Toxic encephalopathy caused by mercury
  • Toxic encephalopathy caused by monomethyl mercury

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to G92.9: its own notes plus those printed at Chapter 6. A note printed at a category, block or chapter applies to every code under it.

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 6 (G00-G99) Diseases of the nervous system applies to 700 codes
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Code First

The underlying condition named in the note is sequenced before this code.

  • poisoning due to drug or toxin, if applicable, (T36-T65 with fifth or sixth character 1-4)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

  • code for adverse effect, if applicable, to identify drug (T36-T50 with fifth or sixth character 5)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name G92.9, its category, or a range that includes it.

Use Additional Code 1

These codes say to use an additional code from the note, and G92.9 is one of the codes named.

  • G90.81 Serotonin syndrome
    toxic encephalopathy (G92.-) names G92.-, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

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

CCSR INJ030
Drug induced or toxic related condition
Default principal diagnosis: inpatient No · outpatient No
CCSR NVS020
Other nervous system disorders (neither hereditary nor degenerative)
Default principal diagnosis: inpatient Yes · outpatient Yes

Code History & ChangesHistory

Replacement G92.9 replaces the following previously assigned code(s):

  • G92 - Toxic encephalopathy
FY 2022AddedAdded to the ICD-10-CM code setEffective October 1, 2021.
FY 2023–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About G92.9Overview

What is the ICD-10 code for unspecified toxic encephalopathy?

The ICD-10-CM code for unspecified toxic encephalopathy is G92.9 (sometimes written as G929). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is G92.9 (Toxic encephalopathy) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report unspecified toxic encephalopathy on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does G92.9 group to?

When unspecified toxic encephalopathy is the principal diagnosis on an inpatient stay, it groups to MS-DRG 793, 791, 24, 23, 91, 92, 93, with relative weights from 0.7783 to 5.7422 depending on complications. Higher weights mean higher Medicare reimbursement.

Is G92.9 a CC or MCC?

CMS lists G92.9 as an MCC (major complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 47 closely related codes in its exclusion list.

Does G92.9 need an additional code?

When the condition applies, yes. The Use Additional Code note reads: code for adverse effect, if applicable, to identify drug (T36-T50 with fifth or sixth character 5). The additional code is reported after G92.9.