ICD-10-CM
ICD-10 code for Encephalitis: G04.90
The ICD-10-CM index points "Encephalitis" to G04.9 (Encephalitis, myelitis and encephalomyelitis, unspecified), a header that is not billable. When nothing more specific is documented, the billable code is G04.90, Encephalitis and encephalomyelitis, unspecified.
Source: CDC ICD-10-CM FY2027 Alphabetic Index file dated June 16, 2026. Publisher page
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Index subterms
A header groups codes and is not billed. A billable code is one you can report.
- A86acute, Unspecified viral encephalitisBillable
- A85.2arboviral, arbovirus NEC, Arthropod-borne viral encephalitis, unspecifiedBillable
- A85.2arthropod-borne NEC (viral), Arthropod-borne viral encephalitis, unspecifiedBillable
- A83.4Australian, Australian encephalitisBillable
- A83.5California (virus), California encephalitisBillable
- A84.1Central European (tick-borne), Central European tick-borne encephalitisBillable
- A84.1Czechoslovakian, Central European tick-borne encephalitisBillable
- A81.1Dawson's (inclusion body), Subacute sclerosing panencephalitisBillable
- A81.1diffuse sclerosing, Subacute sclerosing panencephalitisBillable
- G04.00disseminated, acute, Acute disseminated encephalitis and encephalomyelitis, unspecifiedBillable
- A83.2Eastern equine, Eastern equine encephalitisBillable
- A86endemic (viral), Unspecified viral encephalitisBillable
- A86epidemic NEC (viral), Unspecified viral encephalitisBillable
- A83.9equine (acute) (infectious) (viral), Mosquito-borne viral encephalitis, unspecifiedBillable
- A84.0Far Eastern (tick-borne), Far Eastern tick-borne encephalitis [Russian spring-summer encephalitis]Billable
- G04.02following vaccination or other immunization procedure, Postimmunization acute disseminated encephalitis, myelitis and encephalomyelitisBillable
- B02.0herpes zoster, Zoster encephalitisBillable
- B00.4herpesviral, Herpesviral encephalitisBillable
- A83.8Ilheus (virus), Other mosquito-borne viral encephalitisBillable
- A81.1inclusion body, Subacute sclerosing panencephalitisBillable
- A86infectious (acute) (virus) NEC, Unspecified viral encephalitisBillable
- A83.0Japanese (B type), Japanese encephalitisBillable
- A83.5La Crosse, California encephalitisBillable
- A85.8lethargica (acute) (infectious), Other specified viral encephalitisBillable
- A84.89louping ill, Other tick-borne viral encephalitisBillable
- M32.19lupus erythematosus, systemic, Other organ or system involvement in systemic lupus erythematosus, and G05.3 for the manifestationBillable
- A87.2lymphatica, Lymphocytic choriomeningitisBillable
- A85.8Mengo, Other specified viral encephalitisBillable
- A39.81meningococcal, Meningococcal encephalitisBillable
- A83.4Murray Valley, Australian encephalitisBillable
- H66.40otitic NEC, Suppurative otitis media, unspecified, unspecified ear, and G05.3 for the manifestationBillable
- B71.9parasitic NOS, Cestode infection, unspecifiedBillable
- G37.0periaxial, Diffuse sclerosis of central nervous systemBillable
- G37.5periaxialis (concentrica) (diffuse), Concentric sclerosis [Balo] of central nervous systemBillable
- B01.11postchickenpox, Varicella encephalitis and encephalomyelitisBillable
- B09postexanthematous NEC, Unspecified viral infection characterized by skin and mucous membrane lesionsBillable
- G04.02postimmunization, Postimmunization acute disseminated encephalitis, myelitis and encephalomyelitisBillable
- G04.01postinfectious NEC, Postinfectious acute disseminated encephalitis and encephalomyelitis (postinfectious ADEM)Billable
- B05.0postmeasles, Measles complicated by encephalitisBillable
- G04.02postvaccinal, Postimmunization acute disseminated encephalitis, myelitis and encephalomyelitisBillable
More specific codes in G04
A header groups codes and is not billed. A billable code is one you can report.
- G04Encephalitis, myelitis and encephalomyelitisHeader
- G04.0Acute disseminated encephalitis and encephalomyelitis (ADEM)Header
- G04.00Acute disseminated encephalitis and encephalomyelitis, unspecifiedBillable
- G04.01Postinfectious acute disseminated encephalitis and encephalomyelitis (postinfectious ADEM)Billable
- G04.02Postimmunization acute disseminated encephalitis, myelitis and encephalomyelitisBillable
- G04.1Tropical spastic paraplegiaBillable
- G04.2Bacterial meningoencephalitis and meningomyelitis, not elsewhere classifiedBillable
- G04.3Acute necrotizing hemorrhagic encephalopathyHeader
- G04.30Acute necrotizing hemorrhagic encephalopathy, unspecifiedBillable
- G04.31Postinfectious acute necrotizing hemorrhagic encephalopathyBillable
- G04.32Postimmunization acute necrotizing hemorrhagic encephalopathyBillable
- G04.39Other acute necrotizing hemorrhagic encephalopathyBillable
- G04.8Other encephalitis, myelitis and encephalomyelitisHeader
- G04.81Other encephalitis and encephalomyelitisBillable
- G04.82Acute flaccid myelitisBillable
- G04.89Other myelitisBillable
- G04.9Encephalitis, myelitis and encephalomyelitis, unspecifiedHeader
- G04.90Encephalitis and encephalomyelitis, unspecifiedBillable
- G04.91Myelitis, unspecifiedBillable
Excludes1
Excludes1 means these codes are not reported together.
From G04. A note on a category applies to every code under it.
Excludes2
Excludes2 means the other condition can be reported with this one when both are documented.
From G04. A note on a category applies to every code under it.
Related conditions
Related pages
- G04.90 code detailsNotes, nearby codes, CMS-HCC group
- Category G04.9Every code under it
- Chapter 6Diseases of the nervous system
- ICD-10 codes by conditionA to Z
- Check a list of ICD-10 codes
- Denial code CO-11Diagnosis does not support the procedure
- Denial code CO-146Diagnosis invalid for the date of service
- HCPCS Level II code lookup
Questions
What is the ICD-10 code for Encephalitis?
The ICD-10-CM index points "Encephalitis" to G04.9 (Encephalitis, myelitis and encephalomyelitis, unspecified), a header that is not billable. When nothing more specific is documented, the billable code is G04.90, Encephalitis and encephalomyelitis, unspecified.
Is G04.90 billable?
Yes. G04.90 is a billable code in the FY2027 ICD-10-CM file. Use a more specific code when the record documents one.
What documentation notes apply to G04.90?
The CDC tabular list gives 1 Excludes1 note (not coded together), 7 Excludes2 notes (may be coded together when both are documented) for G04.90 and the categories above it. They are listed on this page.
What chapter is G04.90 in?
Chapter 6. Diseases of the nervous system.
When do ICD-10-CM codes change?
Every October 1, with the new fiscal year file. Some years add April 1 updates. This page uses the FY2027 file, effective October 1, 2026.