Skip to main content

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

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

Coding at a Glance

Tabular directives
4 inclusion terms · 3 Excludes2 · 1 use-additional code

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 769 — POSTPARTUM AND POST ABORTION DIAGNOSES WITH O.R. PROCEDURES (MDC 14)
  • MS-DRG 776 — POSTPARTUM AND POST ABORTION DIAGNOSES WITHOUT O.R. PROCEDURES (MDC 14)

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 O91.23 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 O91.23 itself; “inherited from” names the category or block whose note applies here.

Inclusion Terms

Alternative terms the tabular list files under this code.

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

Excludes2 — Not Included Here

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

Source: inherited from O85-O92

Use Additional Code

Supplementary codes the tabular list directs you to add.

  • Use additional code to identify infection

Source: inherited from O91

Coder workflow for O91.23

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

Before you code O91.23

  1. O91.23’s title joins a condition with an associated condition or complication. Confirm each component is documented. Where the classification presumes the link through the “with” convention, only a provider statement that the conditions are unrelated defeats it. A combination code is assigned only when it fully identifies the documented conditions; a required second code for the stage, type or manifestation is still reported when the notes ask for it (Guidelines I.B.9, I.A.15).

    Guide: Combination codes →

  2. Confirm the condition is documented as complicating the pregnancy, childbirth, or the puerperium, and check the trimester where the code carries one and the fetus character where the category requires it. Chapter 15 codes belong on the maternal record only and take sequencing priority over codes from other chapters. It is the provider’s responsibility to state that a condition is not affecting the pregnancy; the trimester is assigned from the documentation (Guidelines I.C.15.a, I.C.15.a.1, I.C.15.a.3).

    Guide: How to choose an ICD-10-CM code →

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).
Trimester
Assigned from the documented trimester at the encounter, or the trimester in which the condition developed for inpatient stays (Guidelines I.C.15.a.3).
The associated condition or complication
Whether the associated condition the title names is documented; the “with” convention presumes some links, and a provider statement that the conditions are unrelated defeats it (Guidelines I.A.15).
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.

Official instructions as workflow

  • Excludes2 — not part of O91.23(3 notes)

    Coding workflow: The conditions named in this note are not included in O91.23. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

    CompareF53, A34, M83.0

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

  • Use Additional Code — after identifying O91.23(1 note)

    Coding workflow: Check whether the documentation supports the additional code(s) the note names, and report them with O91.23 when it does. Where the instruction is conditional (“if applicable”, “if known”), it applies only when the record documents the condition.

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

Coding decision scenarios

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

Documentation: Only one of the components this code’s title joins is documented.

Coding question: Is O91.23 supported?

Path: Review the code for the documented component on its own.

Reason: A combination code is assigned only when it fully identifies the documented conditions; otherwise the documented component takes its own code (Guidelines I.B.9).

Documentation: A condition the Use Additional Code note names is documented.

Coding question: Is a second code reported with O91.23?

Path: Review the Use Additional Code note and the code it names.

Reason: The additional code is reported when the record documents the condition; a conditional instruction applies only when its condition is met (Guidelines I.A.13).

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

Nonpurulent mastitis associated with lactation is a billable ICD-10-CM diagnosis code (O91.23).

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

  • Age-restricted: the Medicare Code Editor lists this as a maternity (age 9-64) diagnosis; other ages are presumed incorrect.

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 O91.23 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 7 Excludes1 notes: N60 — Benign mammary dysplasia (via O91.-), N60-N65 — Disorders of breast (N60-N65) (via O91.-), N61 — Inflammatory disorders of breast (via O91.-), N62 — Hypertrophy of breast (via O91.-), N63 — Unspecified lump in breast (via O91.-), N64 — Other disorders of breast (via O91.-), N65 — Deformity and disproportion of reconstructed breast (via O91.-).

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

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 2 MS-DRGs: DRG 769 (MDC 14), DRG 776 (MDC 14).

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

Clinical classification (AHRQ CCSR):PRG027 — Complications specified during the puerperium (default); GEN017 — Nonmalignant breast conditions.

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 categories (Complications specified during the puerperium, Nonmalignant breast conditions).

O91.112 — Abscess of breast associated with pregnancy, second trimester, O91.113 — Abscess of breast associated with pregnancy, third trimester, O91.119 — Abscess of breast associated with pregnancy, unspecified trimester, O91.12 — Abscess of breast associated with the puerperium, O91.13 — Abscess of breast associated with lactation, O91.211 — Nonpurulent mastitis associated with pregnancy, first trimester, O91.212 — Nonpurulent mastitis associated with pregnancy, second trimester, O91.213 — Nonpurulent mastitis associated with pregnancy, third trimester, O91.219 — Nonpurulent mastitis associated with pregnancy, unspecified trimester, O91.22 — Nonpurulent mastitis associated with the puerperium, O92.011 — Retracted nipple associated with pregnancy, first trimester, O92.012 — Retracted nipple associated with pregnancy, second trimester, O92.013 — Retracted nipple associated with pregnancy, third trimester, O92.019 — Retracted nipple associated with pregnancy, unspecified trimester, O92.02 — Retracted nipple associated with the puerperium, O92.03 — Retracted nipple associated with lactation, O92.12 — Cracked nipple associated with the puerperium, O92.13 — Cracked nipple associated with lactation, O92.20 — Unspecified disorder of breast associated with pregnancy and the puerperium, O92.29 — Other disorders of breast associated with pregnancy and the puerperium, +191 more

Same Index main term, other category

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

O90.0 — Disruption of cesarean delivery wound (disruption, cesarean wound), O90.1 — Disruption of perineal obstetric wound (secondary perineal tear), O90.3 — Peripartum cardiomyopathy (cardiomyopathy), O90.41 — Hepatorenal syndrome following labor and delivery (hepatorenal syndrome), O90.49 — Other postpartum acute kidney failure (uremia), O90.5 — Postpartum thyroiditis (thyroiditis), O90.6 — Postpartum mood disturbance (mood disturbance), O90.81 — Anemia of the puerperium (anemia), O90.89 — Other complications of the puerperium, not elsewhere classified (neuritis), O90.9 — Complication of the puerperium, unspecified (disease), O92.02 — Retracted nipple associated with the puerperium (retracted nipple), O92.12 — Cracked nipple associated with the puerperium (fissure, nipple), O92.13 — Cracked nipple associated with lactation (fissure, nipple, associated with lactation), O92.29 — Other disorders of breast associated with pregnancy and the puerperium (induration breast), O92.3 — Agalactia (failure, lactation), O92.4 — Hypogalactia (failure, lactation, partial), O92.6 — Galactorrhea (galactorrhea), O92.70 — Unspecified disorders of lactation (disorder, lactation), O98.03 — Tuberculosis complicating the puerperium (infection, maternal, tuberculosis), O98.13 — Syphilis complicating the puerperium (infection, maternal, syphilis), +79 more

Contextual Map

Every relationship of O91.23 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 O91.23 with these 7 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes

Clinical classification (CCSR)

MS-DRG Grouper

MDC crossing

  • MDC 14 — Pregnancy, Childbirth and the Puerperium[MDC crossing]: “Pregnancy, Childbirth and the Puerperium — 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. 94 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026

Index entries

  • Mastitis (acute) (diffuse) (nonpuerperal) (subacute), obstetric (interstitial) (nonpurulent), associated with, lactation[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Puerperal, puerperium (complicated by, complications), galactophoritis, associated with lactation[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Puerperal, puerperium (complicated by, complications), lymphangitis, breast, associated with lactation[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Puerperal, puerperium (complicated by, complications), mammitis, associated with lactation[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Puerperal, puerperium (complicated by, complications), mastitis, associated with lactation[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026

Nearest codes (24)

Change history

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

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. "O91.23 — Nonpurulent mastitis associated with lactation." ICD-10-CM FY2026. https://medcoder.ai/icd10/code/o91.23-nonpurulent-mastitis-associated-with-lactation

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Nonpurulent mastitis associated with lactation

No changes since FY2016 — additions, deletions, description changes and billable-status changes are tracked through FY2027 (effective October 1, 2026), 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 O91.23 in its code family, with their registry titles.

View all codes in the O91 family