2027 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 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

J18.1 is a billable ICD-10-CM diagnosis code for lobar pneumonia, unspecified organism. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 193 through 195, 791, 793, 974 through 976. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 129 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Pneumonia (except that caused by tuberculosis).

J18.1 no longer risk-adjusts for Medicare Advantage: it mapped to HCC 115 under the retired CMS-HCC V24 model through payment year 2025 but maps to no category in the live V28 model. It still risk-adjusts in the PACE (CMS-HCC V22) category 115, ESRD (V21) category 115, and ESRD (V24) category 115 for payment year 2027.

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

Medicare Risk Adjustment (HCC)Billing

J18.1 no longer risk-adjusts for Medicare Advantage: it maps to no payment category in the live CMS-HCC V28 model, although it still risk-adjusts in the other CMS models shown below.

CMS-HCC V28 (Medicare Advantage Payment Model)
Not mapped
Dropped in V28 see all codes that no longer risk-adjust
Prior Model (CMS-HCC V24)
HCC 115
V24 retired last contributed to a Medicare Advantage risk score in payment year 2025
Other CMS Models
PACE (CMS-HCC V22): HCC 115 · ESRD (V21): HCC 115 · ESRD (V24): HCC 115
ESRD V21 weights: 0.013 dialysis, 0.143–0.155 functioning graft · ESRD V24 weights: 0.030 dialysis, 0.154–0.248 functioning graft
Part D (RxHCC)
Not mapped
J18.1 does not risk-adjust in the RxHCC prescription drug model

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.

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

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to J18.1: its own notes plus those printed at J18, block J09-J18, and Chapter 10. 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.

From J18 Pneumonia, unspecified organism applies to 5 codes
  • congenital pneumonia (P23.0)
  • drug-induced interstitial lung disorder (J70.2-J70.4)
  • interstitial pneumonia NOS (J84.9)
  • neonatal aspiration pneumonia (P24.-)
  • pneumonitis due to fumes and vapors (J68.0)
  • usual interstitial pneumonia (J84.178)

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.

From J18 Pneumonia, unspecified organism applies to 5 codes
  • abscess of lung with pneumonia (J85.1)
  • aspiration pneumonia due to anesthesia during labor and delivery (O74.0)
  • aspiration pneumonia due to anesthesia during pregnancy (O29)
  • aspiration pneumonia due to anesthesia during puerperium (O89.0)
  • aspiration pneumonia due to solids and liquids (J69.-)
  • aspiration pneumonia NOS (J69.0)
  • lipid pneumonia (J69.1)
  • pneumonitis due to external agents (J67-J70)
From Block J09-J18 Influenza and pneumonia applies to 53 codes
  • allergic or eosinophilic pneumonia (J82)
  • aspiration pneumonia NOS (J69.0)
  • meconium pneumonia (P24.01)
  • neonatal aspiration pneumonia (P24.-)
  • pneumonia due to solids and liquids (J69.-)
  • congenital pneumonia (P23.9)
  • lipid pneumonia (J69.1)
  • rheumatic pneumonia (I00)
  • ventilator associated pneumonia (J95.851)
From Chapter 10 (J00-J99) Diseases of the respiratory system applies to 366 codes
  • 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)
  • smoke inhalation (T59.81-)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Code First

The underlying condition named in the note is sequenced before this code.

From J18 Pneumonia, unspecified organism applies to 5 codes

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Block J09-J18 Influenza and pneumonia applies to 53 codes
  • code, if applicable, to identify resistance to antimicrobial drugs (Z16.-)
From Chapter 10 (J00-J99) Diseases of the respiratory system applies to 366 codes
  • code, where applicable, to identify:
  • exposure to environmental tobacco smoke (Z77.22)
  • exposure to tobacco smoke in the perinatal period (P96.81)
  • history of tobacco dependence (Z87.891)
  • occupational exposure to environmental tobacco smoke (Z57.31)
  • tobacco dependence (F17.-)
  • tobacco use (Z72.0)

Code Also

A second code may be needed to fully describe the condition; the note gives no sequencing direction.

From J18 Pneumonia, unspecified organism applies to 5 codes
  • if applicable, any associated condition such as:
  • aspiration pneumonia (J69.-)

Notes

General instructions on how these codes are used.

From Chapter 10 (J00-J99) Diseases of the respiratory system applies to 366 codes
  • When a respiratory condition is described as occurring in more than one site and is not specifically indexed, it should be classified to the lower anatomic site (e.g. tracheobronchitis to bronchitis in J40).

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name J18.1, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming J18.1: they are not reported together with it, unless the two conditions are unrelated.

  • J13 Pneumonia due to Streptococcus pneumoniae
    lobar pneumonia, unspecified organism (J18.1)

Use Additional Code 1

These codes say to use an additional code from the note, and J18.1 is one of the codes named.

  • J95.89 Other postprocedural complications and disorders of respiratory system, not elsewhere classified
    bacterial or viral pneumonia (J12-J18) names J12-J18, which includes this code

Code Also 1

These codes say J18.1 may also be needed to fully describe the condition. The note gives no sequencing direction.

  • D81.82 Activated Phosphoinositide 3-kinase Delta Syndrome [APDS]
    pneumonia (J12-J18) names J12-J18, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

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

Clinical InformationClinical

  • Pneumonia

    infection of the lung often accompanied by inflammation.

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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About J18.1Overview

What is the ICD-10 code for lobar pneumonia, unspecified organism?

The ICD-10-CM code for lobar pneumonia, unspecified organism is J18.1 (sometimes written as J181). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

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, 2026 through September 30, 2027.

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 195, 793, 791, 193, 194, 974, 976, 975, with relative weights from 0.6062 to 4.2192 depending on complications. Higher weights mean higher Medicare reimbursement.

Is J18.1 a CC or MCC?

CMS lists J18.1 as an MCC (major complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 129 closely related codes in its exclusion list.

Can J18.1 be reported with P23.0?

Not as a rule. The Excludes1 note at J18, which applies to J18.1, lists "congenital pneumonia (P23.0)". 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).

Does J18.1 risk-adjust for Medicare Advantage payment?

Not for Medicare Advantage. J18.1 mapped to HCC 115 in the retired CMS-HCC V24 model, which last determined payment in 2025, but it maps to no category in the live V28 model; see all codes that no longer risk-adjust. It still risk-adjusts in the PACE (CMS-HCC V22) category 115 (Pneumococcal Pneumonia/Empyema/Lung Abscess), ESRD (V21) category 115 (Pneumococcal Pneumonia/Empyema/Lung Abscess), and ESRD (V24) category 115 (Pneumococcal Pneumonia/Empyema/Lung Abscess).