ICD-10-CM 2027
ICD-10 code for chlamydial disease
From the official ICD-10-CM alphabetic index entry “Disease, diseased › chlamydial”. Page updated September 29, 2026.
About coding chlamydial disease
The ICD-10-CM code for chlamydial disease is A74.9 (Chlamydial infection, unspecified). The official index lists 1 more specific code, so check the documentation for details such as type, cause, site or severity before settling on A74.9.
Within A74, choose A74.9 (Chlamydial infection, unspecified) only when documentation doesn't support a more specific option: chlamydial conjunctivitis (A74.0) and other chlamydial diseases (A74.8).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 865 (Viral Illness with MCC, relative weight 1.3485) and DRG 866 (Viral Illness without MCC, relative weight 0.8692), in MDC 18 (Infectious and Parasitic Diseases, Systemic or Unspecified Sites), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
More specific chlamydial disease codes (official index)
- specified NEC A74.89 — Other chlamydial diseases
Common questions about chlamydial disease ICD-10 codes
What is the ICD-10 code for chlamydial disease?
- A74.9 — Chlamydial infection, unspecified. More specific codes apply when the documentation supports them: A74.89.
Is A74.9 billable?
- Yes. A74.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can A74.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict A74.9 as a principal diagnosis.
Is A74.9 a CC or MCC?
- No. A74.9 is neither a CC nor an MCC under MS-DRG v44.0.