2026 ICD-10-CM Diagnosis Code G40.812Lennox-Gastaut syndrome, not intractable, without status epilepticus

ICD-10-CM Codes›G00–G99›G40-G47›G40

ICD-10-CM G40.812
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

G40.812 is a billable ICD-10-CM diagnosis code for Lennox-Gastaut syndrome, not intractable, without status epilepticus. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 100 through 101. Coders also document this condition as Lennox-Gastaut syndrome. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Epilepsy; convulsions.

Code Identity

ICD-10-CM Code
G40.812
Billable Status
Yes — Valid for Submission
Code Describes
Lennox-Gastaut syndrome, not intractable, without status epilepticus
Short Description
Lennox-Gastaut syndrome, not intractable, w/o stat epi
Parent Code
G40.81
Lennox-Gastaut syndrome

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG40-G47Episodic and paroxysmal disorders
CategoryG40Epilepsy and recurrent seizures
This CodeG40.812Lennox-Gastaut syndrome, not intractable, without status epilepticus

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Lennox-Gastaut syndrome
  • Lennox-Gastaut syndrome, non-refractory

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Lennox-Gastaut syndrome
    • Lennox-Gastaut syndrome
      • not intractable
    • Lennox-Gastaut syndrome
      • not intractable
        • without status epilepticus
    • Syndrome
      • Lennox-Gastaut
    • Syndrome
      • Lennox-Gastaut
        • not intractable
    • Syndrome
      • Lennox-Gastaut
        • not intractable
          • without status epilepticus

Clinical ClassificationClinical

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

CCSR NVS009
Epilepsy; convulsions
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Lennox Gastaut Syndrome

    a childhood-onset epilepsy syndrome.

Patient EducationClinical

Epilepsy

Epilepsy is a brain disorder that causes people to have recurring seizures. The seizures happen when clusters of nerve cells, or neurons, in the brain send out the wrong signals. People may have strange sensations and emotions or behave strangely. They may have violent muscle spasms or lose consciousness.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert G40.812 to ICD-9-CMHistory

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

ICD-9-CM
345.80 Epilep NEC w/o intr epil
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About G40.812Overview

Is G40.812 (Lennox-Gastaut syndrome) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report Lennox-Gastaut syndrome, not intractable, without status epilepticus on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does G40.812 group to?

When Lennox-Gastaut syndrome, not intractable, without status epilepticus is the principal diagnosis on an inpatient stay, it groups to MS-DRG 100, 101, with relative weights from 0.9026 to 1.9368 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of G40.812?

Under the General Equivalence Mappings, Lennox-Gastaut syndrome, not intractable, without status epilepticus converts to ICD-9-CM 345.80 (epilep NEC w/o intr epil). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.