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X39.01XS vs Z77.123

X39.01XS (Exposure to radon, sequela) compared with Z77.123 (Contact with and (suspected) exposure to radon and other naturally occurring radiation), 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 should not be reported together because X39.01XS’s tabular entry lists Z77.123 under Excludes1.

Official rule
What is different?

The conditions named and chapter.X39.01XS is “Exposure to radon, sequela”; Z77.123 is “Contact with and (suspected) exposure to radon and other naturally occurring radiation”. X39.01XS sits in V00-Y99 — External Causes of Morbidity (V00-Y99); Z77.123 in Z00-Z99 — Factors Influencing Health Status and Contact with Health Services (Z00-Z99).

Registry fact

Can these codes be reported together?

No.X39.01XS’s entry carries an Excludes1 note covering Z77.123: “contact with and (suspected) exposure to radon and other naturally occurring radiation (Z77.123)”. Both may be reported only when the documentation shows the two conditions are unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Official ruleGuide: Excludes1 vs Excludes2

Is there an Excludes1 relationship?

Yes.X39.01XS’s tabular entry: “contact with and (suspected) exposure to radon and other naturally occurring radiation (Z77.123)”. The note covers Z77.123.

Official ruleGuide: Excludes1 vs Excludes2

Is there an Excludes2 relationship?

Yes.Z77.123’s tabular entry: “radiation exposure as the cause of a confirmed condition (W88-W90, X39.0-)”. The note covers X39.01XS.

Official ruleGuide: Excludes1 vs Excludes2

Nothing found in 3 other checks; 1 check does not apply
Is one more specific?

Not comparable.The codes sit in different categories; specificity is only comparable within one category.

Is one a parent or header code?

No.Both are billable codes, and neither contains the other.

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?

Excludes1 — generally not reported together

Excludes1 conflict

X39.01XS
Exposure to radon, sequela
↔
Z77.123
Contact with and (suspected) exposure to radon and other naturally occurring radiation

What we found

No — do not report together.X39.01XS carries an Excludes1 note covering Z77.123: “contact with and (suspected) exposure to radon and other naturally occurring radiation (Z77.123)”

Sole exception: when the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

What to review

Report one of the two. Both may be reported only when the documentation shows the two conditions are unrelated to each other.

Guide: Excludes1 vs Excludes2Check these on a claim

Why it matters

An Excludes1 note means the two conditions are not ordinarily reported together for the same encounter, because the classification treats them as mutually exclusive forms of the same condition. The documented exception is when the two conditions are unrelated to each other.

Source / rule

CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a

Informational

Excludes2 relationship

Z77.123
Contact with and (suspected) exposure to radon and other naturally occurring radiation
↔
X39.01XS
Exposure to radon, sequela

What we found

Yes, when both are documented.Z77.123 carries an Excludes2 note covering X39.01XS: “radiation exposure as the cause of a confirmed condition (W88-W90, X39.0-)”

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.a — Excludes1 · applies to: Excludes1

    A type 1 Excludes note is a pure excludes note. It means “NOT CODED HERE!” An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition. An exception to the Excludes1 definition is the circumstance when the two conditions are unrelated to each other. If it is not clear whether the two conditions involving an Excludes1 note are related or not, query the provider. For example, code F45.8, Other somatoform disorders, has an Excludes1 note for "sleep related teeth grinding (G47.63)," because "teeth grinding" is an inclusion term under F45.8. Only one of these two codes should be assigned for teeth grinding. However psychogenic dysmenorrhea is also an inclusion term under F45.8, and a patient could have both this condition and sleep related teeth grinding. In this case, the two conditions are clearly unrelated to each other, and so it would be appropriate to report F45.8 and G47.63 together.

    ICD-10-CM Official Guidelines FY2027

  • 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
X39.01XS

Exposure to radon, sequela

Z77.123

Contact with and (suspected) exposure to radon and other naturally occurring radiation

StatusSame for both
Billable
Excludes1Differs
X39.01XS
  • contact with and (suspected) exposure to radon and other naturally occurring radiation (Z77.123)
  • exposure to man-made radiation (W88-W90)
  • exposure to sunlight (X32)
Z77.123

None at this code

Excludes2Differs
X39.01XS

None at this code

Z77.123
  • radiation exposure as the cause of a confirmed condition (W88-W90, X39.0-)
  • radiation sickness NOS (T66)
  • contact with and (suspected) exposure to communicable diseases (Z20.-)
  • exposure to (parental) (environmental) tobacco smoke in the perinatal period (P96.81)
  • newborn affected by noxious substances transmitted via placenta or breast milk (P04.-)
  • occupational exposure to risk factors (Z57.-)
  • retained foreign body (Z18.-)
  • retained foreign body fully removed (Z87.821)
  • toxic effects of substances chiefly nonmedicinal as to source (T51-T65)
Code alsoDiffers
X39.01XS

None at this code

Z77.123
  • any follow-up examination (Z08-Z09)
CategoryDiffers
X39.01XS

X39 Exposure to other forces of nature

Z77.123

Z77 Other contact with and (suspected) exposures hazardous to health

ChapterDiffers
X39.01XS

V00-Y99 — External Causes of Morbidity (V00-Y99)

Z77.123

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

IncludesDiffers
X39.01XS

None at this code

Z77.123
  • contact with and (suspected) exposures to potential hazards to health
7th characterDiffers
X39.01XS
  • The appropriate 7th character is to be added to each code from category X39
Z77.123

None at this code

No Code first and Use additional code 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.

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