2026 ICD-10-CM Diagnosis Code G40.509Epileptic seizures related to external causes, not intractable, without status epilepticus

ICD-10-CM Codes›G00–G99›G40-G47›G40

ICD-10-CM G40.509
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

G40.509 is a billable ICD-10-CM diagnosis code for epileptic seizures related to external causes, 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Epilepsy; convulsions.

Code Identity

ICD-10-CM Code
G40.509
Billable Status
Yes — Valid for Submission
Code Describes
Epileptic seizures related to external causes, not intractable, without status epilepticus
Short Description
Epileptic seiz rel to extrn causes, not ntrct, w/o stat epi
Parent Code
G40.50
Epileptic seizures related to external causes, not intractable

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG40-G47Episodic and paroxysmal disorders
CategoryG40Epilepsy and recurrent seizures
This CodeG40.509Epileptic seizures related to external causes, not intractable, without status epilepticus

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Alcohol withdrawal-induced convulsion
  • Alcohol-induced epilepsy
  • Alcohol-related fit
  • Drug-induced epilepsy
  • Narcotic withdrawal epilepsy
  • Post-traumatic epilepsy
  • Seizure co-occurrent and due to anxiolytic withdrawal
  • Seizure co-occurrent and due to hypnotic withdrawal
  • Seizure co-occurrent and due to psychoactive substance withdrawal
  • Seizure co-occurrent and due to substance withdrawal
  • Seizures due to metabolic disorder
  • Situation-related seizures
  • Stress seizure

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Epileptic seizures related to external causes, NOS

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.

    • Epilepsy, epileptic, epilepsia(attack) (cerebral) (convulsion) (fit) (seizure)
      • related to
        • alcohol
    • Epilepsy, epileptic, epilepsia(attack) (cerebral) (convulsion) (fit) (seizure)
      • related to
        • alcohol
          • not intractable
    • Epilepsy, epileptic, epilepsia(attack) (cerebral) (convulsion) (fit) (seizure)
      • related to
        • alcohol
          • not intractable
            • without status epilepticus
    • Epilepsy, epileptic, epilepsia(attack) (cerebral) (convulsion) (fit) (seizure)
      • related to
        • drugs
    • Epilepsy, epileptic, epilepsia(attack) (cerebral) (convulsion) (fit) (seizure)
      • related to
        • drugs
          • not intractable
    • Epilepsy, epileptic, epilepsia(attack) (cerebral) (convulsion) (fit) (seizure)
      • related to
        • drugs
          • not intractable
            • without status epilepticus
    • Epilepsy, epileptic, epilepsia(attack) (cerebral) (convulsion) (fit) (seizure)
      • related to
        • external causes
    • Epilepsy, epileptic, epilepsia(attack) (cerebral) (convulsion) (fit) (seizure)
      • related to
        • external causes
          • not intractable
    • Epilepsy, epileptic, epilepsia(attack) (cerebral) (convulsion) (fit) (seizure)
      • related to
        • external causes
          • not intractable
            • without status epilepticus
    • Epilepsy, epileptic, epilepsia(attack) (cerebral) (convulsion) (fit) (seizure)
      • related to
        • hormonal changes
    • Epilepsy, epileptic, epilepsia(attack) (cerebral) (convulsion) (fit) (seizure)
      • related to
        • hormonal changes
          • not intractable
    • Epilepsy, epileptic, epilepsia(attack) (cerebral) (convulsion) (fit) (seizure)
      • related to
        • hormonal changes
          • not intractable
            • without status epilepticus
    • Epilepsy, epileptic, epilepsia(attack) (cerebral) (convulsion) (fit) (seizure)
      • related to
        • sleep deprivation
    • Epilepsy, epileptic, epilepsia(attack) (cerebral) (convulsion) (fit) (seizure)
      • related to
        • sleep deprivation
          • not intractable
    • Epilepsy, epileptic, epilepsia(attack) (cerebral) (convulsion) (fit) (seizure)
      • related to
        • sleep deprivation
          • not intractable
            • without status epilepticus
    • Epilepsy, epileptic, epilepsia(attack) (cerebral) (convulsion) (fit) (seizure)
      • related to
        • stress
    • Epilepsy, epileptic, epilepsia(attack) (cerebral) (convulsion) (fit) (seizure)
      • related to
        • stress
          • not intractable
    • Epilepsy, epileptic, epilepsia(attack) (cerebral) (convulsion) (fit) (seizure)
      • related to
        • stress
          • 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

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 G40.509 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 G40.509Overview

Is G40.509 a billable code?

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

What MS-DRG does G40.509 group to?

When epileptic seizures related to external causes, 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 G40.509?

Under the General Equivalence Mappings, epileptic seizures related to external causes, 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.