What is ICD-10 code G40.812?

G40.812 is the ICD-10-CM diagnosis code for Lennox-Gastaut syndrome, not intractable, without status epilepticus. Lennox-Gastaut syndrome, a severe childhood epilepsy with multiple seizure types that can be controlled with medication, not currently in a prolonged seizure state. G40.812 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. G40.812 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. G40.812 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. G40.812 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Which HCC does G40.812 map to under V28?

G40.812 maps to CMS-HCC V28 HCC 201 (Seizure Disorders and Convulsions). The category numbers, labels, and conditions come from the CMS-HCC V28 model file for payment year 2026.

2026 ICD-10-CM G40.812: Lennox-Gastaut syndrome

G40.812 maps to CMS-HCC V28 201. A source-labeled RAF reference is available. Documentation must support MEAT. MEAT criteria · RAF Calculator · HCC Buddy coding tools

ICD-10-CM Code View

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Code lookupG40.812Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the nervous system (G00-G99) / Episodic and paroxysmal disorders (G40-G47)

G40.812

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Lennox-Gastaut syndrome, not intractable, without status epilepticus

Lennox-Gastaut syndrome, a severe childhood epilepsy with multiple seizure types that can be controlled with medication, not currently in a prolonged seizure state.

Buddy Insight

Lennox-Gastaut syndrome without status epilepticus and not intractable represents a rare presentation where this severe epilepsy syndrome is adequately controlled with medication.

CMS-HCC V28

Mapped

HCC 201

Seizure Disorders and Convuls...

Code-level coefficient reference

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

Mapped

HCC 120

HHS-HCC 120 adult, RAF varies...

Code-level coefficient reference

ESRD/PACE

Mapped

HCC 79

Seizure Disorders and Convuls...

Code-level coefficient reference

RXHCC

Mapped

HCC 164

Epilepsy and Other Seizure Di...

Code-level coefficient reference

Code Book Path

Official

G40.8Other epilepsy and recurrent seizures

G40.81Lennox-Gastaut syndrome

G40.812Lennox-Gastaut syndrome, not intractable, without status epilepticus

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for G40.812 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for G40.812 in this effective period.

Related Child Codes

Official

G40.811Lennox-Gastaut syndrome, not intractable, with status epilepticus

G40.813Lennox-Gastaut syndrome, intractable, with status epilepticus

G40.814Lennox-Gastaut syndrome, intractable, without status epilepticus

Includes

Official

ICD-10-CM does not list Includes notes for G40.812 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for G40.812 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for G40.812 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for G40.812 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for G40.812 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Confirmed Lennox-Gastaut syndrome diagnosis

Documentation of seizure types (tonic, atonic, atypical absence)

EEG findings showing slow spike-and-wave pattern

Confirmation seizures are controlled (not intractable)

MEAT Support

HCC Buddy guidance

Confirmed Lennox-Gastaut syndrome diagnosis

Documentation of seizure types (tonic, atonic, atypical absence)

EEG findings showing slow spike-and-wave pattern

Confirmation seizures are controlled (not intractable)

Audit Caution

HCC Buddy guidance

LGS that is 'not intractable' is uncommon — verify documentation truly supports medication responsiveness

Assigning this code without the characteristic triad of features (multiple seizure types, EEG pattern, cognitive impairment)

Not capturing associated intellectual disability or developmental delay as separate diagnoses

Using generic epilepsy codes when LGS is confirmed in the record

Common Mistakes

HCC Buddy guidance

G40.811 — LGS, not intractable, WITH status epilepticus

G40.814 — LGS, INTRACTABLE, without status epilepticus; more common presentation

G40.822 — Epileptic spasms without status epilepticus; distinct from LGS

G40.802 — Other epilepsy without status epilepticus; less specific

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is G40.812 an HCC code?

Yes. G40.812 (Lennox-Gastaut syndrome, not intractable, without status epilepticus) maps to HCC 201, Seizure Disorders and Convulsions under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.245. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: G40.812 is billable and maps to V28 HCC 201, Seizure Disorders and Convulsions. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: G40.812
Description: Lennox-Gastaut syndrome, not intractable, without status epilepticus
HCC (V28): HCC 201 — Seizure Disorders and Convulsions
RAF reference coefficient: 0.245
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 201, Seizure Disorders and Convulsions

0.245

ESRDHCC 79, Seizure Disorders and Convulsions

Not separately weighted

RxHCCHCC 164, Epilepsy and Other Seizure Disorders, Except Intractable Epilepsy

Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work G40.812 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT Criteria for G40.812

For G40.812 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed G40.812 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

G40.812 is the ICD-10-CM diagnosis code for lennox-gastaut syndrome, not intractable, without status epilepticus. Lennox-Gastaut syndrome, a severe childhood epilepsy with multiple seizure types that can be controlled with medication, not currently in a prolonged seizure state. G40.812 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering episodic and paroxysmal disorders (g40-g47).

Under the CMS-HCC V28 risk adjustment model, G40.812 maps to Seizure Disorders and Convulsions (HCC 201) with a source-labeled community, non-dual, aged reference coefficient of 0.245. No V24 mapping is shown for G40.812; use the applicable model and payment year when reviewing the V28 mapping. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

This syndrome typically presents in early childhood with developmental delay and multiple seizure types. Because G40.812 maps to an HCC category, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) before the diagnosis is used for risk adjustment. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for G40.812 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•This syndrome typically presents in early childhood with developmental delay and multiple seizure types
•Document the specific seizure types observed (tonic, atonic, absence) to support the diagnosis

Clinical Significance

Lennox-Gastaut syndrome without status epilepticus and not intractable represents a rare presentation where this severe epilepsy syndrome is adequately controlled with medication. LGS typically involves multiple seizure types, characteristic EEG patterns, and cognitive impairment. Even when seizures are controlled, these patients require ongoing comprehensive care for developmental and neurological needs.

Documentation Requirements

✓Confirmed Lennox-Gastaut syndrome diagnosis
✓Documentation of seizure types (tonic, atonic, atypical absence)
✓EEG findings showing slow spike-and-wave pattern
✓Confirmation seizures are controlled (not intractable)
✓Absence of status epilepticus at the encounter
✓Cognitive and developmental assessment
✓Current medication regimen with response documentation

Commonly Confused Codes

•G40.811: LGS, not intractable, WITH status epilepticus
•G40.814: LGS, INTRACTABLE, without status epilepticus; more common presentation
•G40.822: Epileptic spasms without status epilepticus; distinct from LGS
•G40.802: Other epilepsy without status epilepticus; less specific
•G40.409: Other generalized epilepsy; use when LGS criteria not met