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ICD-10-CM 2027 diagnosis code

G40.301Generalized idiopathic epilepsy and epileptic syndromes, not intractable, with status epilepticus

G40.301 is a valid, billable ICD-10-CM code for generalized idiopathic epilepsy and epileptic syndromes, not intractable, with status epilepticus. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.Short description: Gen idiopathic epilepsy, not intractable, w stat epi

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About G40.301

G40.301 is the ICD-10-CM diagnosis code for generalized idiopathic epilepsy and epileptic syndromes, not intractable, with status epilepticus. It belongs to category G40 (epilepsy and recurrent seizures), block G40-G47 (episodic and paroxysmal disorders) and chapter 6 (diseases of the nervous system). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within G40.30 (generalized idiopathic epilepsy and epileptic syndromes, not intractable), G40.301 is specifically for generalized idiopathic epilepsy and epileptic syndromes, not intractable, with status epilepticus. Related codes cover without status epilepticus (G40.309).

As a secondary diagnosis it is an MCC (major complication or comorbidity), which can move an inpatient stay into the highest-paying "with MCC" MS-DRG of its family, unless the principal diagnosis excludes it.

In MS-DRG v44.0, it is part of the grouping logic for DRG 023 (Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis with MCC or Antineoplastic Implant or Epilepsy with Neurostimulator, relative weight 5.7444), DRG 100 (Seizures with MCC, relative weight 1.9233) and DRG 101 (Seizures without MCC, relative weight 0.8952), in MDC 01 (Diseases and Disorders of the Nervous System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 345.3 (grand mal status).

Notes that apply from higher levels

Instructions written at a parent level also apply to G40.301.

› From G40.3 Generalized idiopathic epilepsy and epileptic syndromes
Code also
  • MERRF syndrome, if applicable (E88.42)
› From G40 Epilepsy and recurrent seizures
Note
  • the following terms are to be considered equivalent to intractable: pharmacoresistant (pharmacologically resistant), treatment resistant, refractory (medically) and poorly controlled
Excludes1
  • conversion disorder with seizures (F44.5)
  • convulsions NOS (R56.9)
  • post traumatic seizures (R56.1)
  • seizure (convulsive) NOS (R56.9)
  • seizure of newborn (P90)
Excludes2

Broader instructions also apply from Chapter 6: Diseases of the nervous system.

Alphabetic index entries

2 entries

Terms in the official ICD-10-CM index that lead to G40.301.

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

ICD-9-CM equivalent

Converter →
  • 345.3Grand mal statusapproximate

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about G40.301

Is G40.301 billable?

Yes. G40.301 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can G40.301 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict G40.301 as a principal diagnosis.

Is G40.301 a CC or MCC?

G40.301 is an MCC (major complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.

What DRG does G40.301 group to?

G40.301 is used in the MS-DRG v44.0 logic for MS-DRG 023 (Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis with MCC or Antineoplastic Implant or Epilepsy with Neurostimulator), MS-DRG 100 (Seizures with MCC) and MS-DRG 101 (Seizures without MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for G40.301?

The CMS General Equivalence Mappings map G40.301 to ICD-9-CM 345.3.