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Z79.631 vs Z79.81

Z79.631 (Long term (current) use of antimetabolite agent) compared with Z79.81 (Long term (current) use of agents affecting estrogen receptors and estrogen levels), from the official CMS tabular data.

Current data releases:ICD-10-CM FY2027 · ICD-10-PCS FY2027 · HCPCS October 2026 · MS-DRG v44 · Medicare Code Editor v44.0 · NCCI PTP Q4 2026 · MUE Q4 2026 · NCD code lists 2026-01 · LCD export September 28, 2026 · All releases and sources

Summary

These codes can be reported together when both conditions are documented, because Z79.631 lists Z79.81 under Excludes2, which marks them as distinct conditions.

Official rule
What is different?

Title wording and billing status.The titles share “Long term (current) use of”; Z79.631 says “antimetabolite agent” where Z79.81 says “agents affecting estrogen receptors and estrogen levels”. Z79.81 is a non-billable header; Z79.631 is billable.

Registry fact

Can these codes be reported together?

Yes, when both are documented.Z79.631 lists Z79.81 under Excludes2: “long term (current) use of agents affecting estrogen receptors and estrogen levels (Z79.81-)”. Excludes2 marks distinct conditions that may both be reported when both are documented.

Official ruleGuide: Excludes1 vs Excludes2

Is there an Excludes2 relationship?

Yes.Z79.631’s tabular entry: “long term (current) use of agents affecting estrogen receptors and estrogen levels (Z79.81-)”. The note covers Z79.81.

Official ruleGuide: Excludes1 vs Excludes2

Is one a parent or header code?

One is a header.Z79.81 is a non-billable header, but Z79.631 is not one of its subdivisions.

Registry fact

Nothing found in 4 other checks
Is there an Excludes1 relationship?

None.Neither entry carries an Excludes1 note that names the other code. Z79.81 carries 1 Excludes1 note covering other codes; the side-by-side table quotes them.

Official rule

Is one more specific?

No.Neither is a subdivision of the other, and neither title is the unspecified form; they describe different conditions within category Z79.

Registry fact

Are there sequencing instructions?

None.Neither entry carries a Code First or Use Additional Code note that names the other.

Official rule

Are there other coding relationships?

None found.No laterality, encounter-phase, Table of Neoplasms, Table of Drugs and Chemicals, or history-versus-active-disease relationship links these codes.

MedCoder-derived

Official rule: a tabular instructional note or a section of the ICD-10-CM Official Guidelines, quoted as published. Registry fact: the codes’ own published attributes (titles, billable status, position in the hierarchy, code set). MedCoder-derived: a reading MedCoder computes from those facts; it is not itself a rule. How to read the labels

Can these codes be reported together?

Informational

Excludes2 relationship

Z79.631
Long term (current) use of antimetabolite agent
↔
Z79.81
Long term (current) use of agents affecting estrogen receptors and estrogen levels

What we found

Yes, when both are documented.Z79.631 carries an Excludes2 note covering Z79.81: “long term (current) use of agents affecting estrogen receptors and estrogen levels (Z79.81-)”

Excludes2 marks distinct conditions — both may be reported when both are documented.

What to review

Report both only when the documentation supports both conditions; otherwise report the one documented.

Guide: Excludes1 vs Excludes2Check these on a claim

Why it matters

An Excludes2 note means the excluded condition is not part of the code above it, but a patient can have both. Report both when both are documented.

Source / rule

CMS ICD-10-CM tabular instructional notes

Official guidance behind these answers

  • Section I.A.12.b — Excludes2 · applies to: Excludes2

    A type 2 Excludes note represents “Not included here.” An excludes2 note indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.

    ICD-10-CM Official Guidelines FY2027

Quoted from the ICD-10-CM Official Guidelines for Coding and Reporting in effect for the release shown. The tabular notes above are the code-level instruction; these sections are the convention that says how such a note is applied. Source document (CMS PDF) · Release and checksum

Side by side

Similar descriptions do not make codes interchangeable. The documentation and the official instructions decide which code applies.

Official descriptionDiffers
Z79.631

Long term (current) use of antimetabolite agent

Z79.81

Long term (current) use of agents affecting estrogen receptors and estrogen levels

StatusDiffers
Z79.631
Billable
Z79.81
Non-billable header

A header is not reported on a claim; a code beneath it is.

Report instead: Z79.810, Z79.811, Z79.818

Excludes1Differs
Z79.631

None at this code

Z79.81
  • hormone replacement therapy (Z79.890)
Excludes2Differs
Only at Z79.631
  • long term (current) use of steroids (Z79.5-)
  • long term (current) use of agents affecting estrogen receptors and estrogen levels (Z79.81-)
Only at Z79.81

No note of its own beyond the shared notes

Shared by both codes (2 notes)
  • drug abuse and dependence (F11-F19)
  • drug use complicating pregnancy, childbirth, and the puerperium (O99.32-)
Code firstDiffers
Z79.631

None at this code

Z79.81
  • , if applicable:
  • malignant neoplasm of breast (C50.-)
  • malignant neoplasm of prostate (C61)
Use additional codeDiffers
Z79.631

None at this code

Z79.81
  • code, if applicable, to identify:
  • estrogen receptor positive status (Z17.0)
  • family history of breast cancer (Z80.3)
  • genetic susceptibility to malignant neoplasm (cancer) (Z15.0-)
  • personal history of breast cancer (Z85.3)
  • personal history of prostate cancer (Z85.46)
  • postmenopausal status (Z78.0)
Code alsoSame for both
  • any therapeutic drug level monitoring (Z51.81)
  • any follow-up examination (Z08-Z09)
CategorySame for both

Z79 Long term (current) drug therapy

ChapterSame for both

Z00-Z99 — Factors Influencing Health Status and Contact with Health Services (Z00-Z99)

IncludesDiffers
Only at Z79.631
  • Long term (current) use of 5-fluorouracil
  • Long term (current) use of 6-mercaptopurine
  • Long term (current) use of cytarabine
  • Long term (current) use of methotrexate
Only at Z79.81

No note of its own beyond the shared notes

Shared by both codes (1 note)
  • long term (current) drug use for prophylactic purposes

No 7th character note at either code.

Notes are the code’s own tabular entry, quoted as published. A note that names the other code is the one the verdict above rests on. In a row that differs, each code’s own notes are listed under it, and the notes every code shares are listed once beneath them.

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Derived from the official CMS ICD-10-CM tabular data (FY2027). A coding-rule comparison, not billing advice: payer-specific edits and medical-necessity policy are outside its scope. All data sources