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J18.9 ICD-10-CM Code: Pneumonia, unspecified organism

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Coding at a Glance

Tabular directives
6 Excludes1 · 14 Excludes2 · 1 use-additional code · 1 code-first instruction · 2 code-also instructions

Inpatient Payment Groups (MS-DRG)

Potential MS-DRG participation — not a DRG assignment.

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v44, Appendix B.

  • MS-DRG 193 — SIMPLE PNEUMONIA AND PLEURISY WITH MCC (MDC 04)
  • MS-DRG 194 — SIMPLE PNEUMONIA AND PLEURISY WITH CC (MDC 04)
  • MS-DRG 195 — SIMPLE PNEUMONIA AND PLEURISY WITHOUT CC/MCC (MDC 04)
  • MS-DRG 791 — PREMATURITY WITH MAJOR PROBLEMS (MDC 15)
  • MS-DRG 793 — FULL TERM NEONATE WITH MAJOR PROBLEMS (MDC 15)
  • MS-DRG 974 — HIV WITH MAJOR RELATED CONDITION WITH MCC (MDC 25)
  • MS-DRG 975 — HIV WITH MAJOR RELATED CONDITION WITH CC (MDC 25)
  • MS-DRG 976 — HIV WITH MAJOR RELATED CONDITION WITHOUT CC/MCC (MDC 25)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for J18.9 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2027Effective: October 1, 2026

Trace:FY2027 changesChange historyRelease, file and checksum

Notes without a marker are published on J18.9 itself; “inherited from” names the category or block whose note applies here.

Excludes1 — Not Coded Here

Conditions generally not reported together with this code (Excludes1) -- an error unless the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Source: inherited from J18

Excludes2 — Not Included Here

Conditions not covered by this code, but which may be reported alongside it when both are present.

Code First

Underlying conditions that must be sequenced before this code.

Source: inherited from J18

Code Also

Additional codes that may be required to fully describe the encounter.

  • Code also, if applicable, any associated condition such as:
  • aspiration pneumonia (J69.-)

Source: inherited from J18

Use Additional Code

Supplementary codes the tabular list directs you to add.

  • Use additional code, if applicable, to identify resistance to antimicrobial drugs (Z16.-)

Source: inherited from J09-J18

Coder workflow for J18.9

MedCoder structured workflow — derived from this code’s own official record

Before you code J18.9

  1. Unspecified does not mean incorrect. When the record gives no greater specificity, J18.9 may be the appropriate code. Check the record for detail that supports a more specific sibling. An unspecified code is for records that do not provide the detail a more specific code needs; a query, not an assumption, is the route to specificity (Guidelines I.A.9.b, I.B.18).

    See the relationships section · Guide: Other vs unspecified (NEC vs NOS) →

  2. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with J18.9. Excludes1 conditions are not reported together with this code unless the record shows they are unrelated (Guidelines I.A.12.a).

    See the official tabular notes

Choose the right path

  1. Does the record document the detail a more specific sibling code needs?
    Yes → Review the specific siblings in this subcategory.
    No → Continue — J18.9 is appropriate when the documentation goes no further.
  2. Does the documentation support a condition named in J18.9’s Excludes1 note?
    Yes → Do not simply proceed: review the excluded code. Both are reported only when the record shows the two conditions are unrelated.
    No → Continue.

    ReviewP23.0, J84.9, P24, J68.0, J84.178

  3. Is the underlying (etiologic) condition the Code First note names documented?
    Yes → Sequence the underlying condition first, then J18.9.
    No → Continue; do not add an underlying condition the record does not document.

    ReviewJ09.X1, J10.0, J11.0

Consider J18.9. Then work the Use Additional Code note and review the Code Also note, and confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement
Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).
The underlying (etiologic) condition
Named in the Code First note; sequenced before this code when documented (Guidelines I.A.13).
The conditions the Use Additional Code note names
Reported with this code when documented; a conditional instruction (“if applicable”, “if known”) applies only when the record supports it.
Any detail beyond this code’s title
What the record states that a more specific sibling code would capture — or its absence, which itself supports the unspecified code.

Official instructions as workflow

  • Excludes1 — check before selecting J18.9(6 notes)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with J18.9: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareP23.0, J84.9, P24, J68.0, J84.178

    See the official tabular notes · Guidelines I.A.12.a

  • Excludes2 — not part of J18.9(14 notes)

    Coding workflow: The conditions named in this note are not included in J18.9. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

    CompareJ85.1, O74.0, O29, O89.0, J69, J69.0

    See the official tabular notes · Guidelines I.A.12.b

  • Code First — sequencing check(1 note)

    Coding workflow: Check whether the underlying or etiologic condition the note names is documented. When it is, sequence it before J18.9. Do not add an underlying condition the record does not document.

    ReviewJ09.X1, J10.0, J11.0

    See the official tabular notes · Guidelines I.A.13

  • Use Additional Code — after identifying J18.9(1 note)

    Coding workflow: Check whether the documentation supports the additional code(s) the note names, and report them with J18.9 when it does. Where the instruction is conditional (“if applicable”, “if known”), it applies only when the record documents the condition.

    ReviewZ16

    See the official tabular notes · Guidelines I.A.13

  • Code Also — related condition(2 notes)

    Coding workflow: Review the related condition when both are documented and the instruction applies. A Code Also note does not fix sequencing; the order follows the circumstances of the encounter.

    ReviewJ69

    See the official tabular notes · Guidelines I.A.17

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Documentation: The provider documents the condition in the terms of this code’s title and records no further detail.

Coding question: Is a more specific sibling code supportable?

Path: Review the subcategory for a sibling that names the missing detail.

Reason: A more specific code needs documentation of the distinguishing element; without it the unspecified code is appropriate, and a provider query is the route to specificity (Guidelines I.A.9.b, I.B.18).

Documentation: Both the condition J18.9 describes and a condition named in its Excludes1 note are documented for the same encounter.

Coding question: Can both codes be reported?

Path: Review the Excludes1 note and the excluded code, and look for a provider statement on whether the two conditions are related.

Reason: Excludes1 means the two are not coded together; the exception is when the record shows the conditions are unrelated to each other (Guidelines I.A.12.a).

ReviewP23.0, J84.9, P24, J68.0, J84.178

Documentation: The underlying condition the Code First note names is documented alongside this condition.

Coding question: How are the two sequenced?

Path: Review the Code First note.

Reason: The underlying condition is sequenced first and the manifestation follows (Guidelines I.A.13).

ReviewJ09.X1, J10.0, J11.0

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Don’t confuse J18.9 with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of J18.9 — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

  • P23.0— Excludes1 conflict (Excludes1 — generally not reported together)

    Not coded here — the tabular list excludes this pair for the same encounter.

    Not reported together with this code, except where the two conditions are documented as unrelated.

    What moves you there: Documentation of congenital pneumonia moves the case to P23.0; the two are not reported together unless documented as unrelated.

    Full comparison: J18.9 vs P23.0 →

  • J70.2— Excludes1 conflict (Excludes1 — generally not reported together)

    Not coded here — the tabular list excludes this pair for the same encounter.

    Not reported together with this code, except where the two conditions are documented as unrelated.

    What moves you there: Documentation of drug-induced interstitial lung disorder moves the case to J70.2; the two are not reported together unless documented as unrelated.

    Full comparison: J18.9 vs J70.2 →

  • J70.4— Excludes1 conflict (Excludes1 — generally not reported together)

    Not coded here — the tabular list excludes this pair for the same encounter.

    Not reported together with this code, except where the two conditions are documented as unrelated.

    What moves you there: Documentation of drug-induced interstitial lung disorder moves the case to J70.4; the two are not reported together unless documented as unrelated.

    Full comparison: J18.9 vs J70.4 →

  • J84.9— Excludes1 conflict (Excludes1 — generally not reported together)

    Not coded here — the tabular list excludes this pair for the same encounter.

    Not reported together with this code, except where the two conditions are documented as unrelated.

    What moves you there: Documentation of interstitial pneumonia NOS moves the case to J84.9; the two are not reported together unless documented as unrelated.

    Full comparison: J18.9 vs J84.9 →

  • P24— Excludes1 conflict (Excludes1 — generally not reported together)

    Not coded here — the tabular list excludes this pair for the same encounter.

    Not reported together with this code, except where the two conditions are documented as unrelated.

    What moves you there: Documentation of neonatal aspiration pneumonia moves the case to P24; the two are not reported together unless documented as unrelated.

    Full comparison: J18.9 vs P24 →

  • J68.0— Excludes1 conflict (Excludes1 — generally not reported together)

    Not coded here — the tabular list excludes this pair for the same encounter.

    Not reported together with this code, except where the two conditions are documented as unrelated.

    What moves you there: Documentation of pneumonitis due to fumes and vapors moves the case to J68.0; the two are not reported together unless documented as unrelated.

    Full comparison: J18.9 vs J68.0 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Code Overview

Pneumonia, unspecified organism is a billable ICD-10-CM diagnosis code (J18.9).

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Indexed Clinical Terms (3)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

Official Coding Guidelines

Official source data — quoted verbatim from the CMS/NCHS Official Guidelines

Official source data — quoted verbatim from the CMS/NCHS Official Guidelines

Verbatim excerpts from the ICD-10-CM Official Guidelines for Coding and Reporting (CMS/NCHS) that govern this code.

Chapter 10: Diseases of the Respiratory System (J00-J99), U07.0 a. Chronic Obstructive Pulmonary Disease [COPD] and Asthma 1) Acute exacerbation of chronic obstructive bronchitis and asthma

Code J95.851, Ventilator associated pneumonia, should be assigned only when the provider has documented ventilator associated pneumonia (VAP). An additional code to identify the organism (e.g., Pseudomonas aeruginosa, code B96.5) should also be assigned. Do not assign an additional code from categories J12-J18 to identify the type of pneumonia.

Chapter 10: Diseases of the Respiratory System (J00-J99), U07.0 a. Chronic Obstructive Pulmonary Disease [COPD] and Asthma 1) Acute exacerbation of chronic obstructive bronchitis and asthma

2) Ventilator associated Pneumonia Develops after Admission A patient may be admitted with one type of pneumonia (e.g., code J13, Pneumonia due to Streptococcus pneumonia) and subsequently develop VAP. In this instance, the principal diagnosis would be the appropriate code from categories J12-J18 for the pneumonia diagnosed at the time of admission. Code J95.851, Ventilator associated pneumonia, would be assigned as an additional diagnosis when the provider has also documented the presence of ventilator associated pneumonia.

Decision Points

The directives on this code's own record, as a pre-claim checklist.

  1. Sequencing: 1 Code First instruction — the underlying condition is sequenced before this code when present. See the Code First notes
  2. 1 Use Additional Code instruction — report the named additional code(s) when the documentation supports them. See the Use Additional Code notes
  3. 2 Code Also notes — a second code may apply; the guidelines leave its sequencing to the circumstances of the encounter. See the Code Also notes
  4. 6 Excludes1 entries — codes named there are generally not reported together with this code (Guidelines I.A.12.a). See the Excludes1 notes
  5. 14 Excludes2 entries — those conditions are not part of this code and may be reported additionally when documented. See the Excludes2 notes

Checklist rows are derived from this code's own official directives; the wording of each check is MedCoder editorial. The official notes themselves are in the sections each row links to.

Verify Before Coding

  • MCC as a secondary diagnosis (FY2027). Can raise the stay's MS-DRG severity tier.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name J18.9 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 1 Excludes1 note: J16 — Pneumonia due to other infectious organisms, not elsewhere classified.

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Referenced by 1 Use Additional Code instruction: J95.89 — Other postprocedural complications and disorders of respiratory system, not elsewhere classified (via J18.-).

These codes instruct coders to additionally report this code when it applies.

Referenced by 1 Code Also instruction: D81.82 — Activated Phosphoinositide 3-kinase Delta Syndrome [APDS] (via J18.-).

These codes suggest coding this condition alongside when both are present.

MS-DRG Grouper Relationships (FY2027)

Potential MS-DRG participation — not a DRG assignment.

FY2027 MS-DRG: MCC — Major Complication or Comorbidity. Reported as a secondary diagnosis, this code raises the stay's MS-DRG severity tier — except when the principal diagnosis is one of 129 clinically related codes on its CMS exclusion list. Does not count toward severity when the stay groups to DRGs 974-976 (HIV with Major Related Condition).

Named in the grouper logic of 8 MS-DRGs: DRG 193 (MDC 04), DRG 194 (MDC 04), DRG 195 (MDC 04), DRG 791 (MDC 15), DRG 793 (MDC 15), DRG 974 (MDC 25), DRG 975 (MDC 25), DRG 976 (MDC 25).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):RSP002 — Pneumonia (except that caused by tuberculosis) (default).

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same clinical process (MS-DRG)

Acts as MCC — raises the severity of other admissions. CMS groups these diagnoses into one MS-DRG principal-diagnosis exclusion process — a CC/MCC on this list never raises severity when the principal diagnosis is also on it.

J15.61 — Pneumonia due to Acinetobacter baumannii, J15.69 — Pneumonia due to other Gram-negative bacteria, J15.7 — Pneumonia due to Mycoplasma pneumoniae, J15.8 — Pneumonia due to other specified bacteria, J15.9 — Unspecified bacterial pneumonia, J16.0 — Chlamydial pneumonia, J16.8 — Pneumonia due to other specified infectious organisms, J18.0 — Bronchopneumonia, unspecified organism, J18.1 — Lobar pneumonia, unspecified organism, J18.8 — Other pneumonia, unspecified organism, J22 — Unspecified acute lower respiratory infection, J44.81 — Bronchiolitis obliterans and bronchiolitis obliterans syndrome, J44.89 — Other specified chronic obstructive pulmonary disease, J44.9 — Chronic obstructive pulmonary disease, unspecified, J47.0 — Bronchiectasis with acute lower respiratory infection, J47.1 — Bronchiectasis with (acute) exacerbation, J47.9 — Bronchiectasis, uncomplicated, J4A.0 — Restrictive allograft syndrome, J4A.8 — Other chronic lung allograft dysfunction, J4A.9 — Chronic lung allograft dysfunction, unspecified, +108 more

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Pneumonia (except that caused by tuberculosis)).

J15.211 — Pneumonia due to Methicillin susceptible Staphylococcus aureus, J15.212 — Pneumonia due to Methicillin resistant Staphylococcus aureus, J15.29 — Pneumonia due to other staphylococcus, J15.3 — Pneumonia due to streptococcus, group B, J15.4 — Pneumonia due to other streptococci, J15.5 — Pneumonia due to Escherichia coli, J15.6 — Pneumonia due to other Gram-negative bacteria, J15.61 — Pneumonia due to Acinetobacter baumannii, J15.69 — Pneumonia due to other Gram-negative bacteria, J15.7 — Pneumonia due to Mycoplasma pneumoniae, J15.8 — Pneumonia due to other specified bacteria, J15.9 — Unspecified bacterial pneumonia, J16.0 — Chlamydial pneumonia, J16.8 — Pneumonia due to other specified infectious organisms, J17 — Pneumonia in diseases classified elsewhere, J18.0 — Bronchopneumonia, unspecified organism, J18.1 — Lobar pneumonia, unspecified organism, J18.8 — Other pneumonia, unspecified organism, J85.1 — Abscess of lung with pneumonia, J95.851 — Ventilator associated pneumonia, +48 more

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main term “Pneumonia”; these codes share that main term but sit in a different category of the Tabular List.

J15.3 — Pneumonia due to streptococcus, group B (in, Streptococcus, group B), J15.4 — Pneumonia due to other streptococci (streptococcal NEC), J15.5 — Pneumonia due to Escherichia coli (Escherichia coli), J15.61 — Pneumonia due to Acinetobacter baumannii (in, Acinetobacter baumannii), J15.69 — Pneumonia due to other Gram-negative bacteria (Proteus), J15.7 — Pneumonia due to Mycoplasma pneumoniae (Mycoplasma), J15.8 — Pneumonia due to other specified bacteria (anaerobes), J15.9 — Unspecified bacterial pneumonia (bacillus), J16.0 — Chlamydial pneumonia (chlamydial), J16.8 — Pneumonia due to other specified infectious organisms (in, specified, organism NEC), J68.0 — Bronchitis and pneumonitis due to chemicals, gases, fumes and vapors (nitrogen dioxide), J69.0 — Pneumonitis due to inhalation of food and vomit (aspiration), J69.1 — Pneumonitis due to inhalation of oils and essences (lipid, lipoid), J69.8 — Pneumonitis due to inhalation of other solids and liquids (aspiration, due to, solids, liquids NEC), J70.0 — Acute pulmonary manifestations due to radiation (radiation), J82.81 — Chronic eosinophilic pneumonia (eosinophilic), J82.82 — Acute eosinophilic pneumonia (eosinophilic, acute), J82.89 — Other pulmonary eosinophilia, not elsewhere classified (allergic), J84.111 — Idiopathic interstitial pneumonia, not otherwise specified (interstitial, chronic), J84.112 — Idiopathic pulmonary fibrosis (interstitial, usual), +78 more

Lab tests where this diagnosis supports Medicare coverage (NCD)

Medicare's National Coverage Determination (NCD) program lists this diagnosis as medical justification for these lab tests.

Blood Glucose Test, HIV Screening Test

Contextual Map

Every relationship of J18.9 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run J18.9 with these 3 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes

Referenced by Use Additional Code instructions

Referenced by Code Also instructions

Clinical classification (CCSR)

MS-DRG Grouper

MDC crossing

  • MDC 04 — Diseases and Disorders of the Respiratory System[MDC crossing]: “Diseases and Disorders of the Respiratory System — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 4,000 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2027
  • MDC 15 — Newborns and Other Neonates with Conditions Originating in Perinatal Period[MDC crossing]: “Newborns and Other Neonates with Conditions Originating in Perinatal Period — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs.”— CMS MS-DRG Definitions Manual · FY2027

Index entries

  • Infection, infected, infective (opportunistic), lung[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Pneumonia (acute) (double) (migratory) (purulent) (septic) (unresolved)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Pneumonia (acute) (double) (migratory) (purulent) (septic) (unresolved), atypical NEC[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026

Nearest codes

Change history

  • FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Relevant guides

Real-World Coding Questions

Questions working coders have asked about this code, answered from official sources and reviewed by an editor.

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2027 tabular list, index and tables, effective October 1, 2026 Release, file and checksum · Publisher’s page
Coding guidelines Official source data
ICD-10-CM Official Guidelines for Coding and Reporting (FY2027), quoted by section Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v44.0 (October 2026) Release, file and checksum · Publisher’s page
Inpatient payment groups Official source data
CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v44 Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder structured relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "J18.9 — Pneumonia, unspecified organism." ICD-10-CM FY2027. https://medcoder.ai/icd10/code/j18.9-pneumonia-unspecified-organism

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Pneumonia, unspecified organism

No changes since FY2016 — additions, deletions, description changes and billable-status changes are tracked through FY2027, and none are recorded for this code. Note changes are tracked from FY2027 only.

Nearest Codes in This Family

Official ICD-10-CM classifications closest to J18.9 in its code family, with their registry titles.

View all codes in the J18 family