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A49.9 ICD-10-CM Code: Bacterial infection, unspecified

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

Coding at a Glance

Tabular directives
5 Excludes1 · 1 Excludes2

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 v43, Appendix B.

  • MS-DRG 867 — OTHER INFECTIOUS AND PARASITIC DISEASES DIAGNOSES WITH MCC (MDC 18)
  • MS-DRG 868 — OTHER INFECTIOUS AND PARASITIC DISEASES DIAGNOSES WITH CC (MDC 18)
  • MS-DRG 869 — OTHER INFECTIOUS AND PARASITIC DISEASES DIAGNOSES WITHOUT CC/MCC (MDC 18)

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 A49.9 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Notes without a marker are published on A49.9 itself; “inherited from” names the category or block whose note applies here.

This page already reflects the FY2027 tabular note taking effect October 1, 2026.

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).

Excludes2 — Not Included Here

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

Source: inherited from A49

Coder workflow for A49.9

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

Before you code A49.9

  1. Unspecified does not mean incorrect. When the record gives no greater specificity, A49.9 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 A49.9. 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 — A49.9 is appropriate when the documentation goes no further.
  2. Does the documentation support a condition named in A49.9’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.

    ReviewR78.81, A39.9, A79.9, A69.9

Consider A49.9. Then 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).
Anatomical site
At the most specific level the record states; a site the classification separates cannot be assumed from a procedure or a measurement.
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 A49.9(5 notes)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with A49.9: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareR78.81, A39.9, A79.9, A69.9

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

  • Excludes2 — not part of A49.9(1 note)

    Coding workflow: The conditions named in this note are not included in A49.9. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

    CompareA74.9

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

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 A49.9 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).

ReviewR78.81, A39.9, A79.9, A69.9

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.

Code Overview

Bacterial infection, unspecified is a billable ICD-10-CM diagnosis code (A49.9).

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 (5)

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.

Verify Before Coding

  • No Medicare Code Editor or MS-DRG Definitions Manual restrictions apply to this code.

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

MS-DRG Grouper Relationships (FY2026)

Potential MS-DRG participation — not a DRG assignment.

FY2026 MS-DRG: not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity for that release.

Named in the grouper logic of 3 MS-DRGs: DRG 867 (MDC 18), DRG 868 (MDC 18), DRG 869 (MDC 18).

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

Clinical classification (AHRQ CCSR):INF003 — Bacterial infections (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 category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Bacterial infections).

+399 more

Same Index main term, other category

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

A09 — Infectious gastroenteritis and colitis, unspecified (in, enteritis, infectious NEC), A18.01 — Tuberculosis of spine (tuberculous, spine), A18.02 — Tuberculous arthritis of other joints (tuberculous), A24.0 — Glanders (due to or associated with, glanders), A25.1 — Streptobacillosis (epidemic erythema), A30.9 — Leprosy, unspecified (in, leprosy), A31.8 — Other mycobacterial infections (due to or associated with, mycobacteria), A39.83 — Meningococcal arthritis (meningococcal), A39.84 — Postmeningococcal arthritis (postmeningococcal), A46 — Erysipelas (due to or associated with, erysipelas), A50.55 — Late congenital syphilitic arthropathy (syphilitic, congenital), A52.16 — Charcôt's arthropathy (tabetic) (syphilitic), A54.42 — Gonococcal arthritis (gonococcal), A69.23 — Arthritis due to Lyme disease (in, Lyme disease), A92.1 — O'nyong-nyong fever (in, O'nyong-nyong), B06.82 — Rubella arthritis (rubella), B26.85 — Mumps arthritis (in, mumps), B34.9 — Viral infection, unspecified (in, viral disease NEC), B42.82 — Sporotrichosis arthritis (in, sporotrichosis), B49 — Unspecified mycosis (mycotic NEC), +194 more

Contextual Map

Every relationship of A49.9 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 A49.9 with this related code in Claim Check

Hierarchy

Excludes1

  • R78.81 — Bacteremia[Excludes1]: “bacteremia NOS (R78.81)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Clinical classification (CCSR)

MS-DRG Grouper

MDC crossing

  • MDC 18 — Infectious and Parasitic Diseases, Systemic or Unspecified Sites[MDC crossing]: “Infectious and Parasitic Diseases, Systemic or Unspecified Sites — 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. 1 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026

Index entries

  • Arthritis, arthritic (acute) (chronic) (nonpyogenic) (subacute), in (due to), bacterial disease[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Disease, diseased, bacterial[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Infection, infected, infective (opportunistic), Bacillus[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Infection, infected, infective (opportunistic), bacterial NOS[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Infection, infected, infective (opportunistic), gram-negative bacilli NOS[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026

Nearest codes

Change history (3)

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 FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v43.1 (April 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 — v43 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. "A49.9 — Bacterial infection, unspecified." ICD-10-CM FY2026. https://medcoder.ai/icd10/code/a49.9-bacterial-infection-unspecified

Change history

  • Upcoming · effective FY2027 — October 1, 2026
    Excludes2 note will be added
    chlamydial infection NOS (A74.9)
    FY2027 changes
  • Upcoming · effective FY2027 — October 1, 2026
    Excludes1 note will be removed
    chlamydial infection NOS (A74.9)
    FY2027 changes
  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Bacterial infection, unspecified

Nearest Codes in This Family

Official ICD-10-CM classifications closest to A49.9 in its code family, with their registry titles.

View all codes in the A49 family