2026 ICD-10-CM Diagnosis Code O91.23Nonpurulent mastitis associated with lactation

ICD-10-CM Codes›O00-O9A›O85-O92›O91

ICD-10-CM O91.23
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

O91.23 is a billable ICD-10-CM diagnosis code for nonpurulent mastitis associated with lactation. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). The code is restricted by the Medicare Code Editor to maternity cases (age 9 through 64). Coders also document this condition as mastitis associated with lactation. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Complications specified during the puerperium and Nonmalignant breast conditions.

Code Identity

ICD-10-CM Code
O91.23
Billable Status
Yes — Valid for Submission
Code Describes
Nonpurulent mastitis associated with lactation
Short Description
Nonpurulent mastitis associated with lactation
Same as the full description in the CMS dataset.
Parent Code
O91.2
Nonpurulent mastitis associated with pregnancy, the puerperium and lactation

Code Classification

ChapterO00-O9APregnancy, childbirth and the puerperium
SectionO85-O92Complications predominantly related to the puerperium
CategoryO91Infections of breast associated with pregnancy, the puerperium and lactation
This CodeO91.23Nonpurulent mastitis associated with lactation

Code EditsBilling

Medicare Code Editor checks that affect claim validity for O91.23.

Maternity diagnoses
The Medicare Code Editor detects inconsistencies in maternity cases by checking a patient's age and any diagnosis on the patient's record. The maternity code edits apply to patients age ange is 9–64 years inclusive (e.g., diabetes in pregnancy, antepartum pulmonary complication).

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Mastitis associated with lactation
  • Nonpurulent mastitis associated with lactation
  • Obstetric non-purulent mastitis

Tabular List NotesGuidance

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

Inclusion Terms

  • Interstitial mastitis associated with lactation
  • Lymphangitis of breast associated with lactation
  • Mastitis NOS associated with lactation
  • Parenchymatous mastitis associated with lactation

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.

    • Mastitis(acute) (diffuse) (nonpuerperal) (subacute)
      • obstetric (interstitial) (nonpurulent)
        • associated with
          • lactation
    • Puerperal, puerperium(complicated by, complications)
      • galactophoritis
        • associated with lactation
    • Puerperal, puerperium(complicated by, complications)
      • lymphangitis
        • breast
          • associated with lactation
    • Puerperal, puerperium(complicated by, complications)
      • mammitis
        • associated with lactation
    • Puerperal, puerperium(complicated by, complications)
      • mastitis
        • associated with lactation

Clinical ClassificationClinical

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

CCSR PRG027
Complications specified during the puerperium
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR GEN017
Nonmalignant breast conditions
Default principal diagnosis: inpatient No · outpatient No

Patient EducationClinical

Breast Diseases

Breast diseases include various conditions and changes in your breast. Most women experience breast changes at some time. Your age, hormone levels, and medicines you take may cause lumps, bumps, and discharges of fluids that are not breast milk.

The full article covers:

  • What are breast diseases?
  • What are the symptoms of breast disease?
  • How are breast diseases diagnosed?
  • What are the treatments for breast disease?

Read the full article at MedlinePlus

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

Convert O91.23 to ICD-9-CMHistory

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

ICD-9-CM
675.82 Breast inf NEC-del w p/p
Approximate The match is approximate rather than exact.
ICD-9-CM
675.84 Breast inf NEC-postpart
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 O91.23Overview

Is O91.23 a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report nonpurulent mastitis associated with lactation on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Who can O91.23 be reported for?

The Medicare Code Editor checks nonpurulent mastitis associated with lactation against patient demographics: this code is intended for maternity cases (age 9 through 64). Claims outside these limits are flagged as inconsistent.

What is the ICD-9 equivalent of O91.23?

Under the General Equivalence Mappings, nonpurulent mastitis associated with lactation converts to ICD-9-CM 675.82 (breast inf NEC-del w p/p) and 675.84 (breast inf NEC-postpart). 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.