2027 ICD-10-CM Diagnosis Code G40.814Lennox-Gastaut syndrome, intractable, without status epilepticus
ICD-10-CM Codes›G00–G99›G40-G47›G40
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 201
- Chronic Condition
G40.814 is a billable ICD-10-CM diagnosis code for Lennox-Gastaut syndrome, intractable, without status epilepticus. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 23, 100 through 101. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 89 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Epilepsy; convulsions.
For Medicare Advantage risk adjustment, G40.814 maps to CMS-HCC Category 201 (Seizure Disorders and Convulsions) under the V28 model, adding a risk factor of about 0.245 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
G40.814 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to G40.814: its own notes plus those printed at G40 and Chapter 6. A note printed at a category, block or chapter applies to every code under it.
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- certain conditions originating in the perinatal period (P04-P96)
- certain infectious and parasitic diseases (A00-B99)
- complications of pregnancy, childbirth and the puerperium (O00-O9A)
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
- endocrine, nutritional and metabolic diseases (E00-E88)
- injury, poisoning and certain other consequences of external causes (S00-T88)
- neoplasms (C00-D49)
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
Notes
General instructions on how these codes are used.
- the following terms are to be considered equivalent to intractable: pharmacoresistant (pharmacologically resistant), treatment resistant, refractory (medically) and poorly controlled
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name G40.814, its category, or a range that includes it.
Excludes1 3
These codes carry an Excludes1 note naming G40.814: they are not reported together with it, unless the two conditions are unrelated.
Excludes2 2
These codes carry an Excludes2 note naming G40.814: its condition is not part of those codes, and both may be reported when the patient has both.
Code First 1
These codes say to code first a condition named in the note, and G40.814 is one of the conditions named.
Use Additional Code 2
These codes say to use an additional code from the note, and G40.814 is one of the codes named.
Code Also 10
These codes say G40.814 may also be needed to fully describe the condition. The note gives no sequencing direction.
- E20.810 Autosomal dominant hypocalcemiaseizure disorder (G40.-, R56.9) names G40.-, which includes this code
- F78.A1 SYNGAP1-related intellectual disabilityepilepsy and recurrent seizures (G40.-) names G40.-, which includes this code
- G04.8 Other encephalitis, myelitis and encephalomyelitisany associated seizure (G40.-, R56.9) names G40.-, which includes this code
- G40.5 Epileptic seizures related to external causesif applicable, associated epilepsy and recurrent seizures (G40.-) names G40.-, which includes this code
- G43.1 Migraine with auraany associated seizure (G40.-, R56.9) names G40.-, which includes this code
- G93.45 Developmental and epileptic encephalopathyepilepsy, by specific type (G40.-) names G40.-, which includes this code
- I67.850 Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathyepilepsy (G40.-) names G40.-, which includes this code
- Q87.85 MED13L syndromeepilepsy and recurrent seizures (G40.-) names G40.-, which includes this code
- QA0 Neurodevelopmental disorders related to specific genetic pathogenic variantsepilepsy, by specific type (G40.-) names G40.-, which includes this code
- Z15.1 Genetic susceptibility to epilepsy and neurodevelopmental disordersepilepsy, by specific type (G40.-) names G40.-, which includes this code
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Lennox-Gastaut syndrome G40.812
intractable G40.814
without status epilepticus G40.814
Syndrome See Also: Disease;
intractable G40.814
without status epilepticus G40.814
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Lennox Gastaut Syndrome
a childhood-onset epilepsy syndrome.
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 G40.814 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About G40.814Overview
What is the ICD-10 code for Lennox-Gastaut syndrome, intractable, without status epilepticus?
The ICD-10-CM code for Lennox-Gastaut syndrome, intractable, without status epilepticus is G40.814 (sometimes written as G40814). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is G40.814 (Lennox-Gastaut syndrome) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report Lennox-Gastaut syndrome, intractable, without status epilepticus on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does G40.814 group to?
When Lennox-Gastaut syndrome, intractable, without status epilepticus is the principal diagnosis on an inpatient stay, it groups to MS-DRG 100, 23, 101, with relative weights from 0.8952 to 5.7422 depending on complications. Higher weights mean higher Medicare reimbursement.
Is G40.814 a CC or MCC?
CMS lists G40.814 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 89 closely related codes in its exclusion list.
Can G40.814 be reported with F44.5?
Not as a rule. The Excludes1 note at G40, which applies to G40.814, lists "conversion disorder with seizures (F44.5)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
What HCC is G40.814?
G40.814 (Lennox-Gastaut syndrome, intractable, without status epilepticus) maps to CMS-HCC Category 201 (Seizure Disorders and Convulsions), commonly written as HCC 201, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 79 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 163.
Does G40.814 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, G40.814 adds a risk adjustment factor of about 0.245 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.131 to 0.245 depending on the payment segment). HCC 201 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 201 category page.
