2026 ICD-10-CM Diagnosis Code A74.9Chlamydial infection, unspecified

ICD-10-CM Codes›A00–B99›A70-A74›A74

ICD-10-CM A74.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A74.9 is a billable ICD-10-CM diagnosis code for chlamydial infection, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 865 through 866. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections.

Code Identity

ICD-10-CM Code
A74.9
Billable Status
Yes — Valid for Submission
Code Describes
Chlamydial infection, unspecified
Short Description
Chlamydial infection, unspecified
Same as the full description in the CMS dataset.
Parent Code
A74
Other diseases caused by chlamydiae

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA70-A74Other diseases caused by chlamydiae
CategoryA74Other diseases caused by chlamydiae
This CodeA74.9Chlamydial infection, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Chlamydia pneumoniae infection
  • Chlamydia trachomatis infection
  • Chlamydia trachomatis infection in mother complicating childbirth
  • Chlamydia trachomatis infection in pregnancy
  • Chlamydial infection
  • Neonatal bacterial conjunctivitis
  • Neonatal chlamydial conjunctivitis
  • Neonatal chlamydial infection
  • Sexually transmitted infectious disease in mother complicating childbirth
  • Trachoma
  • Venereal disease caused by Chlamydia trachomatis
  • Venereal disease in pregnancy

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Chlamydiosis NOS

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.

    • Chlamydia, chlamydial
    • Disease, diseased
      • chlamydial
    • Infection, infected, infective(opportunistic)
      • Chlamydia, chlamydial

Clinical ClassificationClinical

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

CCSR INF003
Bacterial infections
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Trachoma

    a chronic infection of the conjunctiva and cornea caused by chlamydia trachomatis.

  • Chlamydia Trachomatis Antigen Measurement|CTRAG|Chlamydia trachomatis Antigen|Chlamydia trachomatis Antigen

    the determination of the chlamydia trachomatis antigen present in a sample.

  • Chlamydia trachomatis DNA Measurement|CTRDNA|Chlamydia trachomatis DNA|Chlamydia trachomatis DNA

    the determination of the amount of chlamydia trachomatis dna present in a sample.

  • Chlamydia trachomatis IgA Antibody Measurement

    the determination of the amount of chlamydia trachomatis iga antibody present in a sample.

  • Chlamydia trachomatis IgG Antibody Measurement

    the determination of the amount of chlamydia trachomatis igg antibody present in a sample.

  • Chlamydia trachomatis IgM Antibody Measurement

    the determination of the amount of chlamydia trachomatis igm antibody present in a sample.

  • Chlamydia trachomatis Measurement|CTR|Chlamydia trachomatis|Chlamydia trachomatis

    the determination of the amount of chlamydia trachomatis in a biological sample.

  • Chlamydia Trachomatis RNA Measurement|CTRRNA|Chlamydia trachomatis RNA|Chlamydia trachomatis RNA

    the determination of the amount of chlamydia trachomatis rna in a biological sample.

  • Chlamydia trachomatis|CHLAMYDIA TRACHOMATIS|CHLAMYDIA TRACHOMATIS

    a species of facultatively aerobic, gram-negative, coccobacilli assigned to the phylum chlamydiae. this species cannot be grown on an artificial medium, lacks peptidoglycan within the cell wall, forms elementary and reticulate bodies and can be identified using monoclonal antibodies (mabs) to epitopes in the vs 4 region of momp along with dna sequencing. c. trachomatis is an obligate intracellular parasite that can be transmitted through sexual contact causing infections of the genital tract and rectum and infertility in women, as well as cause eye infections.

  • Neonatal Chlamydia Conjunctivitis|Neonatal Chlamydial Conjunctivitis|Neonatal Inclusion Conjunctivitis|Neonatal Trachoma

    inflammation of the conjunctiva in a newborn due to chlamydia trachomatis which was acquired during labor and delivery.

  • Trachoma

    a bacterial infection of the eye caused by chlamydia trachomatis.

Patient EducationClinical

Bacterial Infections

Bacteria are tiny organisms (living things) that have only one cell. Under a microscope, they look like balls, rods, or spirals. They can be found almost everywhere on Earth. There are lots of bacteria in and on your body. In fact, your body has about 10 times more bacteria cells than human cells.

The full article covers:

  • What are bacteria?
  • How do bacterial infections spread?
  • What are the treatments for bacterial infections?
  • Can bacterial infections be prevented?

Read the full article at MedlinePlus

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

Convert A74.9 to ICD-9-CMHistory

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

ICD-9-CM
079.98 Chlamydial infection NOS
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 A74.9Overview

Is A74.9 (Other diseases caused by chlamydiae) a billable code?

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

What MS-DRG does A74.9 group to?

When chlamydial infection, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 865, 866, with relative weights from 0.8696 to 1.4983 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of A74.9?

Under the General Equivalence Mappings, chlamydial infection, unspecified converts to ICD-9-CM 079.98 (chlamydial infection NOS). 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.