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R09.0 vs T58

R09.0 (Asphyxia and hypoxemia) compared with T58 (Toxic effect of carbon monoxide), 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 R09.0’s tabular entry lists T58 under Excludes1.

Official rule
What is different?

The conditions named and chapter.R09.0 is “Asphyxia and hypoxemia”; T58 is “Toxic effect of carbon monoxide”. R09.0 sits in R00-R99 — Symptoms, Signs and Abnormal Clinical and Laboratory Findings, Not Elsewhere Classified (R00-R99); T58 in S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88).

Registry fact

Can these codes be reported together?

No.R09.0’s entry carries an Excludes1 note covering T58: “asphyxia due to carbon monoxide (T58.-)”. 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.R09.0’s tabular entry: “asphyxia due to carbon monoxide (T58.-)”. The note covers T58.

Official ruleGuide: Excludes1 vs Excludes2

Is one a parent or header code?

Both are headers.Both are non-billable headers, and neither contains the other.

Registry fact

Nothing found in 3 other checks; 1 check does not apply
Is there an Excludes2 relationship?

None.Neither entry carries an Excludes2 note that names the other code. R09.0 carries 1 Excludes2 note covering other codes; the side-by-side table quotes them.

Official rule

Is one more specific?

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

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

R09.0
Asphyxia and hypoxemia
↔
T58
Toxic effect of carbon monoxide

What we found

No — do not report together.R09.0 carries an Excludes1 note covering T58: “asphyxia due to carbon monoxide (T58.-)”

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

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

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
R09.0

Asphyxia and hypoxemia

T58

Toxic effect of carbon monoxide

StatusDiffers
R09.0
Non-billable header

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

Report instead: R09.01, R09.02

T58
Non-billable header

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

Report instead: T58.01XA, T58.01XD, T58.01XS, T58.02XA, T58.02XD

Excludes1Differs
R09.0
  • asphyxia due to carbon monoxide (T58.-)
  • asphyxia due to foreign body in respiratory tract (T17.-)
  • birth (intrauterine) asphyxia (P84)
  • hyperventilation (R06.4)
  • traumatic asphyxia (T71.-)
  • acute respiratory distress syndrome (J80)
  • respiratory arrest of newborn (P28.81)
  • respiratory distress syndrome of newborn (P22.0)
  • respiratory failure (J96.-)
  • respiratory failure of newborn (P28.5)
T58
  • contact with and (suspected) exposure to toxic substances (Z77.-)
Excludes2Differs
R09.0
  • hypercapnia (R06.89)
T58

None at this code

Use additional codeDiffers
R09.0

None at this code

T58
  • code(s):
  • for all associated manifestations of toxic effect, such as: respiratory conditions due to external agents (J60-J70)
  • personal history of foreign body fully removed (Z87.821)
  • to identify any retained foreign body, if applicable (Z18.-)
CategoryDiffers
R09.0

R09 Other symptoms and signs involving the circulatory and respiratory system

T58

Is itself a category

ChapterDiffers
R09.0

R00-R99 — Symptoms, Signs and Abnormal Clinical and Laboratory Findings, Not Elsewhere Classified (R00-R99)

T58

S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88)

IncludesDiffers
R09.0

None at this code

T58
  • asphyxiation from carbon monoxide
  • toxic effect of carbon monoxide from all sources
7th characterDiffers
R09.0

None at this code

T58
  • The appropriate 7th character is to be added to each code from category T58

No Code first and Code also 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