G40.909: Epilepsy, unspecified, not intractable, without status epilepticus

The ICD-10-CM code for a documented seizure disorder or epilepsy when the seizure type is not specified, the epilepsy is not documented as intractable, and status epilepticus is not present.

Billable

FY2027

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At a glance

Code Family

G40.9: Epilepsy, unspecified

Condition

Seizure disorder

HCC Mapping (v28)

HCC 201, Seizure Disorders and Convulsions.

DRG Grouping

Principal diagnosis on the logic list for MS-DRG 100 and MS-DRG 101, Seizures with MCC and Seizures without MCC, under the FY2027 MS-DRG v44 grouper.

Family Specificity

Four billable codes built from two axes: intractable or not intractable, and with or without status epilepticus.

Billable

Yes

Which G40.9 code do I assign?

Two axes divide G40.9 at once: intractable against not intractable, and with status epilepticus against without. The prior question is whether the record supports epilepsy at all, because an Excludes1 note at category G40 bars reporting any G40 code together with R56.9 for the same condition.

When documentation says…

Code

Seizure, no epilepsy diagnosis established

R56.9

Unspecified convulsions. The Alphabetic Index sends the unqualified term Seizure to R56.9. An Excludes1 note at category G40 bars reporting R56.9 with any epilepsy code for the same condition.

Seizure disorder

G40.909

Epilepsy, unspecified, not intractable, without status epilepticus. Seizure disorder NOS, Epilepsy NOS and Recurrent seizures NOS are inclusion terms at G40.909. The unqualified phrase seizure disorder indexes to this code rather than to R56.9.

Status epilepticus, epilepsy not described as refractory

G40.901

Epilepsy, unspecified, not intractable, with status epilepticus. The sixth character records status epilepticus. Documented status epilepticus for the encounter is what moves the code off G40.909.

Refractory epilepsy, no status epilepticus

G40.919

Epilepsy, unspecified, intractable, without status epilepticus. A note at category G40 treats pharmacoresistant, treatment resistant, refractory and poorly controlled as equivalent to intractable. Any of those words moves the fifth character from 0 to 1.

Intractable epilepsy with status epilepticus

G40.911

Epilepsy, unspecified, intractable, with status epilepticus. Both axes move at once. This is the only code in G40.9 that carries intractability and status epilepticus together.

Seizures after head injury, epilepsy not diagnosed

R56.1

Post traumatic seizures. R56.1 carries an Excludes1 note for post traumatic epilepsy. Once the provider documents post traumatic epilepsy, assign the applicable G40 code in place of R56.1.

Childhood absence epilepsy

G40.A09

Absence epileptic syndrome, not intractable, without status epilepticus. A named epileptic syndrome moves the encounter out of G40.9. Juvenile myoclonic epilepsy moves it to the G40.B codes.

Tabular notes

EXCLUDES1

Category G40 carries an Excludes1 note for conversion disorder with seizures (F44.5), convulsions NOS (R56.9), post traumatic seizures (R56.1), seizure (convulsive) NOS (R56.9) and seizure of newborn (P90). G40.909 inherits all of them. Excludes1 means the codes are not reported together for the same condition. Where the provider documents an unqualified seizure or convulsion rather than epilepsy, R56.9 replaces G40.909 rather than accompanying it. G40.89, other seizures, carries its own Excludes1 note naming recurrent seizures NOS (G40.909). G40.89 and G40.909 are not reported together for the same condition either.

EXCLUDES2

Category G40 carries an Excludes2 note for hippocampal sclerosis (G93.81), mesial temporal sclerosis (G93.81), temporal sclerosis (G93.81) and Todd's paralysis (G83.84). Excludes2 permits dual coding. A patient with epilepsy and documented temporal sclerosis may carry both G40.909 and G93.81. A patient with postictal weakness documented as Todd's paralysis may carry both G40.909 and G83.84.

FY2027: EFFECTIVE 1 OCTOBER 2026

G40.909 is unchanged in the FY2027 update. The FY2027 codes and tabular addenda add, delete or revise no code or note in category G40 or category R56.

Operational & financial impact

Why specificity matters beyond the chart: risk adjustment, DRG assignment and denial exposure all follow from which code is selected.

CMS-HCC v28 (PY2024+)

HCC 201, Seizure Disorders and Convulsions.

Published CMS-HCC v28 category code lists place G40.909 in HCC 201. They place R56.9, R56.1, R56.00 and R56.01 in the same category. The v28 category does not separate epilepsy from unspecified convulsions.

CMS-HCC v28 is at full weight for payment year 2026.

For Medicare Advantage risk adjustment, the epilepsy must be documented as evaluated or managed within the calendar year. The code must appear on a dated encounter note rather than only on a problem list.

V24 TO V28 RENUMBERING

Under CMS-HCC v24 the category was numbered HCC 79, Seizure Disorders and Convulsions.

Under CMS-HCC v28 the same clinical category is numbered HCC 201.

The renumbering is not a deletion. Epilepsy remains a risk adjusting condition under v28.

MS-DRG v44 (FY2027)

G40.909 sits on the principal diagnosis logic list for MS-DRG 100, Seizures with MCC, and MS-DRG 101, Seizures without MCC.

G40.909 also groups to surgical MS-DRG 023 when a neurostimulator is implanted. Its v44 title is Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis with MCC or Antineoplastic Implant or Epilepsy with Neurostimulator.

R56.9 and R56.1 also group to MS-DRG 100 or 101, Seizures with MCC or without MCC, as principal diagnoses, but Appendix B lists neither under MS-DRG 023. In a medical admission, reporting R56.9 in place of G40.909 does not by itself move the DRG.

Medicare and commercial payers

NCD 160.18 covers vagus nerve stimulation for patients with medically refractory partial onset seizures for whom surgery is not recommended or has failed.

That coverage language turns on two things G40.909 does not carry: medically refractory and partial onset. Refractory focal epilepsy with complex partial seizures documented to that standard codes to G40.219.

WHERE SPECIFICITY IS LOST

G40.909 names neither the seizure type nor the epilepsy syndrome.

Assigning G40.909 when the note says refractory or poorly controlled understates intractability. The note at category G40 treats those words as equivalent to intractable.

Assigning G40.909 for an encounter in which status epilepticus was treated loses the sixth character that records it.

Assigning R56.9 for a patient with an established epilepsy diagnosis reports a symptom in place of the disease. The Excludes1 note at category G40 bars reporting the two together for the same condition.

Assigning G40.909 when a named syndrome is documented loses the detail available in the G40.A, G40.B and G40.C codes.

SEVERITY DESIGNATION (MS-DRG V44.0)

G40.909 carries no severity designation. It appears in neither Appendix G, the CC list, nor Appendix H, the MCC list, of the ICD-10 MS-DRG Definitions Manual Version 44.0. A case reaches the higher tier of its DRG pair on a designation carried by another diagnosis.

Documentation checklist to support G40.909

Chart elements that support code selection and reduce specificity-driven denials.

Provider documentation of epilepsy, a seizure disorder or recurrent seizures as an established diagnosis.

A record showing that no seizure type or epilepsy syndrome has been determined, which is what supports the unspecified fourth character.

Absence of the words intractable, refractory, pharmacoresistant, treatment resistant and poorly controlled. Any of those moves the fifth character from 0 to 1.

Absence of status epilepticus for the encounter. Documented status epilepticus moves the sixth character from 9 to 1.

A distinction between an established epilepsy diagnosis and an isolated or unexplained seizure. The second is R56.9, which is not reported with G40.909 for the same condition.

Antiseizure medication, EEG findings or imaging that shows the epilepsy is being monitored or treated.

For Medicare Advantage risk adjustment, a dated encounter note within the calendar year showing evaluation or management of the epilepsy.

For outpatient encounters, a confirmed diagnosis. A suspected or rule out seizure disorder is not coded as epilepsy in the outpatient setting.

Where seizures follow head trauma, whether the provider has diagnosed post traumatic epilepsy or only post traumatic seizures. The second is R56.1.

FAQ

Is G40.909 a billable code?

Yes. G40.909 is billable at the sixth character. The parent codes G40.9 and G40.90 are not billable and cannot be reported on a claim.

Is seizure disorder coded G40.909 or R56.9?

Seizure disorder without further qualification is coded G40.909. Seizure disorder NOS and Recurrent seizures NOS are inclusion terms at G40.909. The unqualified term seizure, used where no epilepsy diagnosis has been established, indexes to R56.9 instead. An Excludes1 note at category G40 bars reporting the two together for the same condition.

Does G40.909 map to an HCC under CMS-HCC v28?

Yes. Published CMS-HCC v28 category code lists place G40.909 in HCC 201, Seizure Disorders and Convulsions. The same clinical category was numbered HCC 79 under CMS-HCC v24. R56.9, R56.1 and the febrile convulsion codes appear in HCC 201 as well. The v28 category does not separate epilepsy from unspecified convulsions.

What must the record show to support G40.909?

An established diagnosis of epilepsy, a seizure disorder or recurrent seizures. No stated seizure type or epilepsy syndrome. No documentation of intractability, which includes the words refractory, pharmacoresistant, treatment resistant and poorly controlled. No status epilepticus for the encounter.

What counts as intractable for the fifth character?

A note at category G40 states that pharmacoresistant, pharmacologically resistant, treatment resistant, refractory, medically refractory and poorly controlled are all equivalent to intractable. Any of those terms moves G40.909 to G40.919. With status epilepticus documented as well, the code becomes G40.911.

How is G40.909 sequenced?

Sequence G40.909 as the principal or first listed diagnosis when the epilepsy is the reason for the encounter. Where a seizure workup is the reason for the encounter and epilepsy has not been established, the symptom code R56.9 is reported instead. Where epileptic seizures are documented as related to alcohol, drugs, sleep deprivation, stress or hormonal change, the G40.5 codes carry a Code also instruction for the associated epilepsy.

Does the setting change how G40.909 is used?

Yes. In the outpatient setting, code only a confirmed diagnosis. A suspected, probable or rule out seizure disorder is not coded as epilepsy. On the inpatient side, a diagnosis documented as uncertain at discharge may be coded as though established, under the UHDDS guideline for uncertain diagnoses. G40.909 sits on the principal diagnosis logic list for MS-DRG 100 and MS-DRG 101 under the FY2027 MS-DRG v44 grouper.

What changed for G40.909 in FY2027?

G40.909 is unchanged in the FY2027 update, effective 1 October 2026. The FY2027 codes and tabular addenda add, delete or revise no code or note in category G40.

Related codes

Codes in the same family as G40.909. Only codes with a published page render as links.

Sibling codes in the G40.9 family

G40.901: Epilepsy, unspecified, not intractable, with status epilepticus.
G40.911: Epilepsy, unspecified, intractable, with status epilepticus.
G40.919: Epilepsy, unspecified, intractable, without status epilepticus.

Additional codes to consider

Codes outside the G40.9 family considered alongside G40.909.

Companion: code alongside when documented

G93.81: Temporal sclerosis, including hippocampal and mesial temporal sclerosis, permitted alongside G40.909 by the Excludes2 note at category G40.
G83.84: Todd's paralysis (postepileptic), permitted alongside G40.909 by the Excludes2 note at category G40.
G93.45: Developmental and epileptic encephalopathy, which carries a Code also instruction for epilepsy by specific type.
Z79.899: Other long term (current) drug therapy, where chronic antiseizure medication is documented, under Guideline I.C.21.c.3.

Consider instead

R56.9: Unspecified convulsions, for a seizure where no epilepsy diagnosis has been established.
R56.1: Post traumatic seizures, where the provider has not diagnosed post traumatic epilepsy.
R56.00: Simple febrile convulsions.
R56.01: Complex febrile convulsions.
F44.5: Conversion disorder with seizures or convulsions, for dissociative or functional seizures.
P90: Convulsions of newborn.
G40.209: Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with complex partial seizures, not intractable, without status epilepticus.
G40.309: Generalized idiopathic epilepsy and epileptic syndromes, not intractable, without status epilepticus.
G40.409: Other generalized epilepsy and epileptic syndromes, not intractable, without status epilepticus.
G40.509: Epileptic seizures related to external causes, not intractable, without status epilepticus.
G40.A09: Absence epileptic syndrome, not intractable, without status epilepticus.
G40.B09: Juvenile myoclonic epilepsy, not intractable, without status epilepticus.
G40.89: Other seizures, which carries an Excludes1 note naming recurrent seizures NOS (G40.909).

Sources

All claims on this page derive from government and professional-standards sources.

National Center for Health Statistics. (2026). International classification of diseases, tenth revision, clinical modification (ICD-10-CM) FY2027 files. https://www.cdc.gov/nchs/icd/icd-10-cm/files.html
Centers for Medicare & Medicaid Services and National Center for Health Statistics. (2026). ICD-10-CM official guidelines for coding and reporting FY2027. https://ftp.cdc.gov/pub/Health_Statistics/NCHS/Publications/ICD10CM/2027/ICD-10-CM-October-1-2026-FY27-Guidelines.pdf
Centers for Medicare & Medicaid Services. (2025). 2026 model software/ICD-10 mappings. https://www.cms.gov/medicare/payment/medicare-advantage-rates-statistics/risk-adjustment/2026-model-software-icd-10-mappings
Centers for Medicare & Medicaid Services. (2026). MS-DRG classifications and software, version 44. https://www.cms.gov/medicare/payment/prospective-payment-systems/acute-inpatient-pps/ms-drg-classifications-and-software