ICD-10-CM 2027
ICD-10 code for lung infection
From the official ICD-10-CM alphabetic index entry “Infection, infected, infective (opportunistic) › lung”. Page updated September 29, 2026.
About coding lung infection
The ICD-10-CM code for lung infection is J18.9 (Pneumonia, unspecified organism). The official index lists 2 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on J18.9.
Within J18, choose J18.9 (Pneumonia, unspecified organism) only when documentation doesn't support a more specific option: Bronchopneumonia, unspecified organism (J18.0), Lobar pneumonia, unspecified organism (J18.1), Hypostatic pneumonia, unspecified organism (J18.2) and other pneumonia, unspecified organism (J18.8).
Code first: , if applicable, associated influenza (J09.X1, J10.0-, J11.0-).
As a secondary diagnosis it is an MCC (major complication or comorbidity), which can move an inpatient stay into the highest-paying "with MCC" MS-DRG of its family, unless the principal diagnosis excludes it.
More specific lung infection codes (official index)
Common questions about lung infection ICD-10 codes
What is the ICD-10 code for lung infection?
- J18.9 — Pneumonia, unspecified organism. More specific codes apply when the documentation supports them: A31.0, A69.8.
What is the ICD-10 code for atypical mycobacterium lung infection?
- A31.0 — Pulmonary mycobacterial infection.
What is the ICD-10 code for spirochetal lung infection?
- A69.8 — Other specified spirochetal infections.
Is J18.9 billable?
- Yes. J18.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can J18.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict J18.9 as a principal diagnosis.
Is J18.9 a CC or MCC?
- J18.9 is an MCC (major complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.