What Does ICD-10 Code G40.911 Mean?
ICD-10-CM code G40.911 describes epilepsy, unspecified, intractable, with status epilepticus — a billable, valid diagnosis code for FY 2026 (October 1, 2025 through September 30, 2026). It belongs to the G40 category (Epilepsy and recurrent seizures) within Chapter 6 of ICD-10-CM (Diseases of the Nervous System).
Breaking down the code’s three embedded data points:
- Epilepsy type: Unspecified — the epilepsy syndrome cannot be further classified from available documentation
- Intractability: Confirmed — seizures are not adequately controlled despite appropriate antiepileptic drug (AED) therapy
- Status epilepticus: Present — the provider has documented a seizure episode lasting more than five minutes, or a series of seizures without full recovery in between
This code was introduced with ICD-10-CM implementation in FY 2016 and has carried no description changes since. Per ICD-10-CM Official Coding Guidelines Section I.C.6, unspecified codes are appropriate only when the clinical record does not support a more specific epilepsy classification.
What Conditions Does G40.911 Cover — and What Does It Exclude?
G40.911 applies when a provider has established an epilepsy diagnosis that meets all three criteria above but cannot — or has not yet — specified the seizure type or epilepsy syndrome. Clinical presentations that may appropriately fall under this code include:
- Patients with a confirmed epilepsy diagnosis whose seizure semiology is mixed or undetermined
- Cases where EEG findings are non-localizing and neuroimaging has not identified a structural cause
- Transfer or consultation encounters where the originating provider documented “intractable epilepsy with status epilepticus” without further syndrome classification
- Patients on two or more failed AED regimens who present in active status epilepticus
What Does G40.911 Specifically Exclude?
The G40 category carries several important Excludes 1 notes, meaning these conditions must never be coded simultaneously with G40.911:
- F44.5 — Conversion disorder with seizures (non-epileptic seizure disorder)
- R56.9 — Convulsions, NOS (use only when epilepsy has NOT been established)
- R56.1 — Post-traumatic seizures (distinct from post-traumatic epilepsy)
- P90 — Seizure of newborn
Additionally, Excludes 2 notes (meaning the conditions may be coded together when documented) include hippocampal sclerosis (G93.81) and Todd’s paralysis (G83.84).
In practice, coders frequently encounter the F44.5 vs. G40.911 distinction in neurology and psychiatry settings. The key: a formal epilepsy diagnosis from a treating neurologist must exist in the record before G40.911 can be assigned.
When Is G40.911 the Right Code to Use?
Selecting G40.911 over the other G40.9xx codes requires a systematic check of three documentation criteria. Use this workflow every time:
- Confirm epilepsy is established. The provider must have documented a diagnosis of epilepsy — not just “seizure” or “possible seizure disorder.” A history of epilepsy from a prior encounter qualifies if it remains active.
- Confirm intractability. The record must reflect that seizures are pharmacoresistant, treatment-resistant, refractory, medically poorly controlled, or that the patient has failed at least two appropriate AED trials. Per the ICD-10-CM Official Coding Guidelines, all of these terms are accepted synonyms for intractable.
- Confirm status epilepticus is documented. The provider must explicitly document status epilepticus, or describe a clinical event consistent with it (prolonged seizure >5 minutes, or repetitive seizures without interictal recovery). Coders should not infer status epilepticus from nursing notes alone — it requires provider attestation.
- Confirm the epilepsy type cannot be further specified. If the provider has documented focal-onset, generalized, or a named syndrome, a more specific G40 code applies (see comparison table below).
How Does G40.911 Differ From G40.919 and G40.909?
| Code | Epilepsy Type | Intractable? | Status Epilepticus? | When to Use |
|---|---|---|---|---|
| G40.911 | Unspecified | Yes | Yes | Intractable epilepsy, NOS, with documented status epilepticus |
| G40.919 | Unspecified | Yes | No | Intractable epilepsy, NOS, without status epilepticus at this encounter |
| G40.909 | Unspecified | No | No | Epilepsy, NOS, responding to treatment, no status epilepticus |
| G40.901 | Unspecified | No | Yes | Non-intractable epilepsy with status epilepticus — a rare but valid combination |
The single most common coding error in this code family is assigning G40.911 when G40.919 is correct — because the coder defaults to the “higher acuity” code without confirming status epilepticus is documented for the current encounter.
What Documentation Is Required to Support G40.911?
What Must the Provider Document in the Clinical Notes?
A claim billed with G40.911 should be supported by documentation that explicitly addresses all three axes of the code. Auditors reviewing G40.911 claims will look for:
- A clear epilepsy diagnosis statement — not just “seizure history” or “recurrent events”
- Language establishing intractability: “refractory to levetiracetam and valproate,” “poorly controlled despite adequate AED dosing,” “pharmacoresistant epilepsy”
- An explicit reference to status epilepticus — including onset time, duration, and treatment administered (e.g., benzodiazepine administration, EEG monitoring)
- Provider attestation in the assessment/plan — not just a nursing flowsheet or EMS report
- Distinction from non-epileptic seizure disorder if psychogenic events are also in the differential
Which Diagnostic or Lab Results Support This Code?
- EEG findings documenting abnormal ictal or interictal epileptiform activity
- Neuroimaging reports (MRI brain) — even if normal, the absence of structural cause is clinically relevant and should be noted
- Therapeutic drug level results confirming adequate AED dosing during the failed treatment period
- Transfer or consultation notes from neurologists or epileptologists confirming the intractability diagnosis
- ICU monitoring records when status epilepticus required continuous EEG (cEEG) monitoring
What Is the Documentation Standard for Inpatient vs. Outpatient Settings?
| Setting | Documentation Standard | Key Difference |
|---|---|---|
| Inpatient | Discharge summary must support all three axes; attending physician query acceptable | Coding from discharge summary; all conditions treated during the stay may be coded |
| Outpatient | Encounter note must reflect active management of G40.911 at that specific visit | Code only conditions documented and addressed at that encounter |
| Emergency Department | Provider must document status epilepticus in the ED note — EMS report alone is insufficient | High audit risk if status epilepticus is referenced only in EMS documentation |
How Does G40.911 Affect Medical Billing and Claims?
G40.911 carries significant reimbursement implications, particularly in the inpatient setting. Key billing considerations include:
- MS-DRG assignment: G40.911 as a principal diagnosis groups to MS-DRG 023 (Craniotomy with Major Device Implant or Acute Complex CNS Diagnosis with MCC, or Epilepsy with Neurostimulator) or MS-DRG 024/025 depending on complications and comorbidities — this distinction can shift reimbursement by thousands of dollars per case
- Status epilepticus adds MCC-level weight in DRG logic; failing to code G40.911 when it is documented (and instead using G40.919) results in significant under-coding
- Outpatient: E/M level must reflect the complexity documented; intractable epilepsy with status epilepticus typically supports high-complexity medical decision-making (MDM Level 4 or 5)
- Medical necessity: Payers require documentation that supports the intractable designation; claims without AED treatment history are audit targets
What CPT or Procedure Codes Are Commonly Billed With G40.911?
| CPT Code | Description | Typical Pairing Context |
|---|---|---|
| 95816 | EEG, awake and drowsy | Initial workup or follow-up evaluation |
| 95951 | EEG monitoring, prolonged (hospital) | Status epilepticus monitoring |
| 95726 | Continuous EEG monitoring (cEEG), each 24 hours | ICU status epilepticus management |
| 99285–99291 | ED E/M or critical care | Emergency presentation in status epilepticus |
| 95970–95976 | Neurostimulator programming | VNS or RNS management in refractory cases |
| 90863 | Pharmacologic management | Medication management visits |
Are There Any Prior Authorization or Coverage Restrictions?
- Most commercial payers require prior authorization for neurostimulator implantation (VNS, RNS) billed alongside a G40.911 diagnosis
- Some payers apply medical necessity review to prolonged EEG monitoring — clinical documentation must establish that continuous monitoring was required for status epilepticus management
- Medicare LCD policies for epilepsy monitoring vary by MAC jurisdiction; coders should verify applicable LCDs at CMS.gov before submitting claims for extended monitoring services
- Ketogenic diet therapy and certain investigational AEDs may require prior authorization with supporting clinical records
What Coding Errors Should You Avoid With G40.911?
Auditors and internal coding quality reviews consistently identify the same error patterns with this code. Ranked by frequency:
- Assigning G40.911 without documented status epilepticus — the most common error; coders see “intractable epilepsy” and select the higher-acuity code without verifying status epilepticus is documented for the encounter
- Using G40.911 when a more specific epilepsy type is documented — if the neurologist has written “intractable focal epilepsy with status epilepticus,” the correct code is from the G40.01x series, not G40.911
- Coding status epilepticus from EMS or nursing notes only — provider documentation is required; EMS documentation alone does not satisfy the coding standard
- Failing to code G40.911 at all on inpatient claims — when status epilepticus is treated during an admission but not listed as a principal or secondary diagnosis, the DRG grouping is materially understated
- Confusing “poorly controlled” with “intractable” — while ICD-10-CM does accept “poorly controlled” as equivalent to intractable, the provider must actually use this language; coders cannot infer intractability from a high seizure frequency alone
What Do Auditors Look for When Reviewing Claims With G40.911?
- Provider attestation of status epilepticus in the assessment/plan section — not just in the HPI
- Evidence of failed AED trials documented in the medication history or progress notes
- Correlation between the diagnosis code and the services billed (e.g., prolonged monitoring, ICU-level care)
- Absence of Excludes 1 code conflicts (particularly F44.5 or R56.9 appearing on the same claim)
- Query-and-response documentation when the original note is ambiguous about intractability or status epilepticus
How Does G40.911 Relate to Other ICD-10 Codes?
Understanding G40.911 within the broader G40 code family prevents both under-coding and specificity errors.
| Related Code | Relationship | Key Distinction |
|---|---|---|
| G40.919 | Sibling code | Same epilepsy type and intractability; status epilepticus absent or not documented |
| G40.909 | Sibling code | Epilepsy unspecified, not intractable, no status epilepticus |
| G40.011/G40.111/G40.211 | More specific alternatives | Focal epilepsy, intractable, with status epilepticus — use when seizure onset is documented |
| G40.311/G40.411 | More specific alternatives | Generalized epilepsy syndromes, intractable, with status epilepticus |
| G93.81 | Excludes 2 (may co-code) | Hippocampal/mesial temporal sclerosis — code additionally when documented as a comorbidity |
| G83.84 | Excludes 2 (may co-code) | Todd’s paralysis following a seizure — assign additionally when documented |
| F44.5 | Excludes 1 (never co-code) | Non-epileptic attack disorder; mutually exclusive with G40.911 |
What Is the Correct Code Sequencing When G40.911 Appears With Other Diagnoses?
- Inpatient: If the patient was admitted for status epilepticus management, G40.911 is the principal diagnosis (the condition determined after study to have occasioned the admission).
- Outpatient: Sequence G40.911 first only when it is the primary reason for the encounter; if the visit addressed a separate chief complaint with epilepsy as a comorbidity, sequence the encounter reason first.
- When a causative condition is known: If structural epilepsy has a documented etiology (e.g., brain tumor, post-stroke), follow the code also or use additional code conventions; the underlying condition may be sequenced first depending on the setting and reason for encounter.
- Neurostimulator encounters: When the primary purpose of the visit is VNS or RNS programming, the procedure-related encounter code may sequence first; G40.911 serves as the supporting diagnosis explaining why the device exists.
Real-World Coding Scenario — How G40.911 Is Applied in Practice
Patient encounter: A 34-year-old male with a five-year history of epilepsy presents to the emergency department after his wife calls 911. EMS documents a generalized tonic-clonic seizure lasting 12 minutes before lorazepam was administered en route. In the ED, the attending neurologist documents: “Patient has known epilepsy, unresponsive to levetiracetam and lamotrigine despite therapeutic levels. Today’s event represents status epilepticus, now broken with IV benzodiazepine. He will be admitted for monitoring and AED adjustment.” The patient is admitted to the neurology unit for two days. No specific epilepsy syndrome has been established across prior evaluations.
Correct Code Application
- Principal diagnosis: G40.911 — Epilepsy, unspecified, intractable, with status epilepticus
- Rationale: All three axes are met — epilepsy is established, intractability is supported by two failed AEDs at therapeutic levels, and the attending has explicitly documented status epilepticus. The syndrome remains unspecified, so G40.911 is the most accurate code available.
- Additional codes to consider: G93.81 if hippocampal sclerosis is documented on MRI; Z79.899 for long-term AED use
Common Mistake in This Scenario
- Incorrect code: G40.919 (Epilepsy, unspecified, intractable, without status epilepticus)
- Why it fails: The coder skips over the status epilepticus documentation because it appeared in the EMS note and the ED narrative rather than a dedicated “status epilepticus” section. The attending’s assessment is explicit; the correct code is G40.911. This error results in under-coding the MCC-level severity, potentially shifting the DRG grouping and reducing reimbursement.
Frequently Asked Questions About ICD-10 Code G40.911
Is ICD-10 Code G40.911 Valid for Use in 2026?
G40.911 remains a fully valid, billable diagnosis code for FY 2026, covering claims with dates of service from October 1, 2025 through September 30, 2026. No description changes or validity updates have been applied to this code since its introduction in FY 2016. Coders should confirm annually against the CMS ICD-10-CM tabular list release for each fiscal year.
What Is the Difference Between G40.911 and G40.919?
G40.911 and G40.919 both describe intractable, unspecified epilepsy, but G40.911 is used only when status epilepticus is documented for the encounter, while G40.919 applies when it is absent or not documented. The distinction has major inpatient reimbursement consequences: status epilepticus functions as an MCC in DRG grouping logic, and selecting G40.919 when G40.911 is correct constitutes material under-coding.
What Documentation Is Required to Code G40.911 Versus a More Specific Epilepsy Code?
G40.911 is appropriate only when the provider has not documented a specific epilepsy syndrome or seizure-onset type. If the neurologist has identified focal-onset seizures, generalized epilepsy, or a named syndrome such as Lennox-Gastaut, the coder must select from the corresponding G40.0x, G40.1x, G40.2x, or G40.3x subcategories with the intractable/status epilepticus axis applied.
Can G40.911 Be Used in Outpatient Settings?
Yes, G40.911 is valid in both inpatient and outpatient settings. In an outpatient context, however, the provider’s encounter note — not just a historical problem list — must reflect active management of intractable epilepsy with status epilepticus at that specific visit. Routine follow-up visits managing a patient whose status epilepticus resolved in a prior inpatient stay would typically be coded as G40.919 unless a new episode of status epilepticus occurred and was managed at that outpatient encounter.
Is G40.911 an Acceptable Diagnosis Code for Medicare Claims?
G40.911 is accepted by Medicare for HIPAA-covered claims. Medical necessity must be supported by documentation of intractable epilepsy and status epilepticus. Coders should verify applicable Medicare LCD policies through their regional MAC for specific services billed alongside this code, including prolonged EEG monitoring and neurostimulator management.
What Is the ICD-9 Equivalent of G40.911?
The approximate ICD-9-CM equivalent is 345.91 (Epilepsy, unspecified, with intractable epilepsy). The mapping is approximate — ICD-9 did not distinguish status epilepticus as a separate axis within the epilepsy code structure, so the conversion is not exact. Claims-based analyses comparing ICD-9 and ICD-10 epilepsy data should account for this structural difference per AHA Coding Clinic guidance on crosswalk limitations.
Key Takeaways
Every coder working with G40.911 should keep these principles top of mind:
- G40.911 requires three elements to be documented simultaneously: epilepsy (not just seizure), intractability, and status epilepticus — all three must be provider-attested
- “Intractable” encompasses pharmacoresistant, treatment-resistant, refractory, medically poorly controlled, and poorly controlled per ICD-10-CM Official Coding Guidelines
- Status epilepticus must be documented by the treating provider — nursing notes and EMS records alone do not meet the coding standard
- In the inpatient setting, correct use of G40.911 versus G40.919 can directly affect MS-DRG assignment and reimbursement
- When a more specific epilepsy syndrome is documented, G40.911 is not appropriate — move to the corresponding focal or generalized epilepsy subcategory
- G40.911 carries several Excludes 1 notes; never code it alongside F44.5, R56.9, R56.1, or P90 on the same claim
- Verify annually that G40.911 remains unchanged in the current fiscal year’s CMS ICD-10-CM tabular list release
For more on coding complex neurological diagnoses, review the ICD-10-CM Official Coding Guidelines Section I.C.6 and consult the AHA Coding Clinic for epilepsy-specific Q&A guidance.