2026 ICD-10-CM Diagnosis Code J18.1Lobar pneumonia, unspecified organism

ICD-10-CM Codes›J00–J99›J09-J18›J18

ICD-10-CM J18.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

J18.1 is a billable ICD-10-CM diagnosis code for lobar pneumonia, unspecified organism. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 193 through 195, 974 through 976. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Pneumonia (except that caused by tuberculosis).

Code Identity

ICD-10-CM Code
J18.1
Billable Status
Yes — Valid for Submission
Code Describes
Lobar pneumonia, unspecified organism
Short Description
Lobar pneumonia, unspecified organism
Same as the full description in the CMS dataset.
Parent Code
J18
Pneumonia, unspecified organism

Code Classification

ChapterJ00–J99Diseases of the respiratory system
SectionJ09-J18Influenza and pneumonia
CategoryJ18Pneumonia, unspecified organism
This CodeJ18.1Lobar pneumonia, unspecified organism

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Basal pneumonia
  • Consolidation of lung present
  • Left lower zone pneumonia
  • Left upper zone pneumonia
  • Lingular pneumonia
  • Lobar pneumonia
  • Lung consolidation
  • Right lower zone pneumonia
  • Right middle zone pneumonia
  • Right upper zone pneumonia
  • Unresolved lobar pneumonia
  • Unresolved pneumonia

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Pneumonia(acute) (double) (migratory) (purulent) (septic) (unresolved)
      • lobar (disseminated) (double) (interstitial)

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR RSP002
Pneumonia (except that caused by tuberculosis)
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Pneumonia

Pneumonia is an infection in one or both of your lungs. It causes the air sacs of your lungs to fill up with fluid or pus. Pneumonia can range from mild to severe, depending on what caused it, your age, and your overall health.

The full article covers:

  • What is pneumonia?
  • What causes pneumonia?
  • Who is more likely to develop pneumonia?
  • What are the symptoms of pneumonia?
  • What other problems can pneumonia cause?
  • How is pneumonia diagnosed?
  • What are the treatments for pneumonia?
  • Can pneumonia be prevented?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert J18.1 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
481 Pneumococcal pneumonia
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About J18.1Overview

Is J18.1 (Pneumonia, unspecified organism) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report lobar pneumonia, unspecified organism on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does J18.1 group to?

When lobar pneumonia, unspecified organism is the principal diagnosis on an inpatient stay, it groups to MS-DRG 193, 194, 195, 974, 975, 976, with relative weights from 0.6285 to 2.8860 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of J18.1?

Under the General Equivalence Mappings, lobar pneumonia, unspecified organism converts to ICD-9-CM 481 (pneumococcal pneumonia). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.