J18.9: Pneumonia, unspecified organism

The ICD-10-CM code for pneumonia when the causative organism is not identified in the record and no anatomical pattern such as lobar pneumonia or bronchopneumonia is documented.

Billable

FY2027

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At a glance

Code Family

J18: Pneumonia, unspecified organism.

HCC Mapping (v28)

No HCC mapping. J18.9 does not map to any CMS-HCC v28 category.

Condition

Pneumonia

Billable

Yes

Effective Date

Valid in the FY2026 code set and unchanged in the FY2027 update.

Family Specificity

Five billable child codes split on the anatomical pattern of the pneumonia. J18.9 is the residual code when neither the organism nor the pattern is documented.

Which J18 code do I assign?

The J18 family splits on the anatomical pattern the note describes rather than on severity. The prior question is whether an organism is identified at all, because a documented organism moves the encounter out of category J18. The Index sends it to an organism-specific code in J09–J17 or, for organisms such as Candida (B37.1) and Pneumocystis (B59), to a Chapter 1 code.

When documentation says…

Code

Pneumonia, organism not identified

J18.9

Pneumonia documented as a confirmed diagnosis with no causative organism identified. The note must not specify an anatomical pattern such as lobar pneumonia or bronchopneumonia.

Bronchopneumonia

J18.0

Bronchopneumonia with no identified organism. The note must state the bronchopneumonia pattern.

Lobar pneumonia

J18.1

Lobar pneumonia with no identified organism. The note must state lobar involvement.

Sputum culture positive for Streptococcus pneumoniae

J13

Pneumonia due to Streptococcus pneumoniae. An organism classifiable to J09–J17 takes the organism-specific code instead of J18.9.

Pneumonitis following aspiration of food or vomit

J69.0

Pneumonitis due to inhalation of food and vomit, where aspiration is the documented mechanism. Category J18 carries an Excludes2 note for aspiration pneumonia. Both codes may be reported when each condition is independently documented.

Pneumocystis pneumonia

B59

Pneumocystosis. Pneumocystis pneumonia is classified to B59 rather than to category J18.

Sepsis with pneumonia as the underlying infection

A41.9

Sepsis, unspecified organism. When sepsis is the reason for admission, the sepsis code is sequenced first and J18.9 follows as the localized infection. When sepsis develops after admission, J18.9 is sequenced first (Guideline I.C.1.d.4).

Tabular notes

USE ADDITIONAL

Category J18 carries no Use additional note for an organism code. A documented organism moves the pneumonia out of category J18 to its organism-specific code in J09–J17 or in Chapter 1, such as B37.1 for Candida and B59 for Pneumocystis. The Index sends Pneumonia, bacterial, specified NEC to J15.8 and Pneumonia, viral, specified NEC to J12.89. Block J09–J18 carries a Use additional note, if applicable, to identify resistance to antimicrobial drugs (the Z16 codes). Chapter 10 carries a Use additional note, where applicable, for tobacco exposure, history, dependence and use.

EXCLUDES1

Congenital pneumonia is excluded from category J18 and is coded to the P23 codes. Neonatal aspiration pneumonia is excluded and is coded to the P24 codes. The note also lists usual interstitial pneumonia (J84.178). The Index sends usual interstitial pneumonia to J84.112, and to J84.178 only when it is due to collagen vascular disease or in diseases classified elsewhere. The note further lists drug-induced interstitial lung disorder (J70.2–J70.4), interstitial pneumonia NOS (J84.9) and pneumonitis due to fumes and vapors (J68.0). An Excludes1 note means the excluded condition is not reported together with J18.9 for the same pneumonia.

EXCLUDES2

Category J18 carries Excludes2 notes for abscess of lung with pneumonia (J85.1), aspiration pneumonia NOS (J69.0), lipid pneumonia (J69.1) and aspiration pneumonia due to solids and liquids (the J69 codes). An Excludes2 note permits dual coding when both conditions are present and independently documented.

FY2027: EFFECTIVE 1 OCTOBER 2026

No codes were added to or deleted from category J18 for FY2026. No Use Additional or Excludes note changes were identified for J18.9 or for the J18 parent category. The FY2027 codes and tabular addenda make no addition, deletion or revision in category J18.

Operational & financial impact

Why specificity matters beyond the chart: risk adjustment, DRG assignment and denial exposure all follow from which code is selected.

CMS-HCC v28 (PY2024+)

J18.9 does not map to any Hierarchical Condition Category under CMS-HCC Model Version 28.

CMS-HCC v28 is fully operative at 100 percent weight for Medicare Advantage payment year 2026.

Unspecified pneumonia is not a risk adjusting condition under the current CMS model.

Pneumonia complicated by sepsis may reach HCC-carrying codes in the A41 sepsis range. Code the sepsis separately when it meets the definition in the ICD-10-CM guidelines.

INPATIENT DRG ASSIGNMENT

J18.9 drives inpatient DRG assignment for pneumonia hospitalizations.

With J18.9 as the principal diagnosis, the case groups to MS-DRG 193, 194 or 195, Simple Pneumonia and Pleurisy, in MDC 04 under the FY2027 MS-DRG v44 grouper.

Sequence J18.9 as the principal or primary diagnosis when pneumonia is the reason for the encounter or the admission.

When sepsis is the reason for admission, the sepsis code is sequenced first under ICD-10-CM guidelines Section I.C.1.d.4, and J18.9 follows as the localized infection. When the patient is admitted with pneumonia and sepsis develops after admission, J18.9 is sequenced first, followed by the sepsis code.

MEDICARE AND COMMERCIAL PAYERS

There is no National Coverage Determination specific to J18.9.

J18.9 generates no HCC risk adjustment weight under CMS-HCC v28.

WHERE SPECIFICITY IS LOST

Assigning J18.9 when an organism-specific code exists, such as J13 for Streptococcus pneumoniae or J12.89 for other viral pneumonia.

Assigning J18.9 as the principal diagnosis when sepsis was the reason for admission.

Reporting J18.9 for COVID-19 pneumonia without U07.1.

Documentation checklist to support J18.9

Chart elements that support code selection and reduce specificity-driven denials.

Provider documentation of pneumonia as a confirmed diagnosis.

A statement that no causative organism was identified, or a record in which no organism is named.

The absence of a documented anatomical pattern such as lobar pneumonia or bronchopneumonia, either of which would direct the encounter to J18.1 or J18.0.

Culture, antigen or other laboratory results, to establish whether an organism-specific code in J09–J17 or Chapter 1 applies instead.

The organism name where one is documented, to support the organism-specific code in J09–J17 or Chapter 1.

Any documented aspiration of food, vomit, oils or other solids and liquids, which directs the encounter to the J69 codes.

Whether sepsis criteria are met and when sepsis developed. The sepsis code is sequenced before J18.9 when sepsis is the reason for admission.

For outpatient encounters, a confirmed diagnosis only. Possible or probable pneumonia is coded to the presenting symptoms in the outpatient setting.

FAQ

Is J18.9 a billable code?

Yes. J18.9 is a valid billable code. It is the unspecified organism code for pneumonia, used when no causative organism is identified and no anatomical pattern is documented.

When should I use J18.9 instead of J13?

Use J13 when the record identifies Streptococcus pneumoniae as the cause. Use J18.9 when no causative organism is identified in the record. An organism classifiable to J09–J17 always takes the organism-specific code.

Which organism code do I add to J18.9?

No organism code is added to J18.9. Category J18 carries no Use additional note for an organism, because J18.9 is the code for an unidentified organism. A documented organism moves the pneumonia to its organism-specific code, such as J13 for Streptococcus pneumoniae. The Index sends some organisms to Chapter 1 instead, such as Candida to B37.1 and Pneumocystis to B59. The Index sends other specified bacterial pneumonia to J15.8 and other specified viral pneumonia to J12.89. Block J09–J18 carries a Use additional note, if applicable, for resistance to antimicrobial drugs (the Z16 codes).

Does J18.9 map to an HCC?

No. J18.9 does not map to any category in CMS-HCC Model Version 28. Unspecified pneumonia is not a risk adjusting condition under the current CMS model. CMS-HCC v28 is fully operative at 100 percent weight for payment year 2026.

What must the note show to support J18.9?

The note must show pneumonia documented as a confirmed diagnosis, no identified causative organism and no documented anatomical pattern such as lobar pneumonia or bronchopneumonia.

How do I sequence J18.9 when the patient also has sepsis?

Sequence the sepsis code first when sepsis criteria are met, under ICD-10-CM guidelines Section I.C.1.d. J18.9 follows as the underlying infection site. Code J18.9 alone when sepsis is not documented or the criteria are not met.

Can I code probable pneumonia?

Probable pneumonia is not coded as confirmed in the outpatient setting. Code the presenting symptoms such as cough or fever when the diagnosis is not confirmed. On the inpatient side, probable or suspected pneumonia documented at discharge may be coded under the UHDDS uncertain diagnosis guidelines.

Did J18.9 change in FY2027?

J18.9 is unchanged in the FY2027 update. No codes were added to or deleted from category J18 for FY2026. No Use Additional or Excludes note changes were identified for J18.9 or for the J18 parent category. The FY2027 codes and tabular addenda, effective October 1, 2026, make no addition, deletion or revision in category J18 either.

Related codes

Codes in the same family as J18.9. Only codes with a published page render as links.

Sibling codes in the J18 family

J18.0: Bronchopneumonia, unspecified organism.
J18.1: Lobar pneumonia, unspecified organism.
J18.2: Hypostatic pneumonia, unspecified organism.
J18.8: Other pneumonia, unspecified organism.

Additional codes to consider

Codes outside the J18 family considered alongside J18.9.

Companion: code alongside when documented

A41.9: Sepsis, unspecified organism, sequenced before J18.9 when sepsis is the reason for admission.

Consider instead

J13: Pneumonia due to Streptococcus pneumoniae.
J14: Pneumonia due to Hemophilus influenzae.
J15.1: Pneumonia due to Pseudomonas.
J12.89: Other viral pneumonia, where a virus other than COVID-19 is identified.
J69.0: Pneumonitis due to inhalation of food and vomit, where aspiration is the documented mechanism.
B59: Pneumocystosis, for Pneumocystis pneumonia.

U07.1: COVID-19, sequenced first when the pneumonia is documented as due to COVID-19.

J84.178: Other interstitial pulmonary diseases with fibrosis in diseases classified elsewhere, for usual interstitial pneumonia due to collagen vascular disease or in diseases classified elsewhere.
J84.112: Idiopathic pulmonary fibrosis, where the Index sends usual interstitial pneumonia NOS.

Sources

All claims on this page derive from government and professional-standards sources.

National Center for Health Statistics. (2026). International classification of diseases, tenth revision, clinical modification (ICD-10-CM) FY2027 files. https://www.cdc.gov/nchs/icd/icd-10-cm/files.html
Centers for Medicare & Medicaid Services and National Center for Health Statistics. (2026). ICD-10-CM official guidelines for coding and reporting FY2027. https://ftp.cdc.gov/pub/Health_Statistics/NCHS/Publications/ICD10CM/2027/ICD-10-CM-October-1-2026-FY27-Guidelines.pdf
Centers for Medicare & Medicaid Services. (2025). 2026 model software/ICD-10 mappings. https://www.cms.gov/medicare/payment/medicare-advantage-rates-statistics/risk-adjustment/2026-model-software-icd-10-mappings
Centers for Medicare & Medicaid Services. (2026). MS-DRG classifications and software, version 44. https://www.cms.gov/medicare/payment/prospective-payment-systems/acute-inpatient-pps/ms-drg-classifications-and-software