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T58.94XS ICD-10-CM Code: Toxic effect of carbon monoxide from unspecified source, undetermined, sequela

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

Coding at a Glance

7th character
Required — see the character table on this page
Tabular directives
2 inclusion terms · 1 Excludes1 · 4 use-additional codes

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 922 — OTHER INJURY, POISONING AND TOXIC EFFECT DIAGNOSES WITH MCC (MDC 21)
  • MS-DRG 923 — OTHER INJURY, POISONING AND TOXIC EFFECT DIAGNOSES WITHOUT MCC (MDC 21)

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 T58.94XS in the official ICD-10-CM tabular list, quoted as published.

Notes without a marker are published on T58.94XS itself; “inherited from” names the category or block whose note applies here.

Includes

Conditions the official ICD-10-CM tabular list includes under this code.

  • asphyxiation from carbon monoxide
  • toxic effect of carbon monoxide from all sources

Source: inherited from T58

Excludes1 — Not Coded Here

Conditions generally not reported together with this code (Excludes1) -- an error unless the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Source: inherited from T51-T65

Use Additional Code

Supplementary codes the tabular list directs you to add.

  • Use additional 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.-)

Source: inherited from T51-T65

7th Character Guide

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

  • A — initial encounter
  • D — subsequent encounter
  • S — sequela (this page’s code)

How the encounter character is assigned. “Initial encounter” means the patient is receiving active treatment for the condition — it is not limited to the first visit, and a different or new provider giving active treatment still assigns it. “Subsequent encounter” covers care during the healing or recovery phase after active treatment. “Sequela” is for complications or conditions that arise as a direct result of the original condition.

ICD-10-CM Official Guidelines for Coding and Reporting, Section I.C.19.a (paraphrased by MedCoder).

Variant codes in this family

T58.94XA, T58.94XD, T58.94XS

Character meanings are CMS's official 7th-character extensions for this family, as carried in each variant code's official description; variant codes are registry rows. The explanation of how the encounter character is assigned is MedCoder editorial, distinct from the official content above it.

Code Overview

Toxic effect of carbon monoxide from unspecified source, undetermined, sequela is a billable ICD-10-CM diagnosis code (T58.94XS).

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Decision Points

The directives on this code's own record, as a pre-claim checklist.

  1. A 7th character applies in this family. Confirm the documented encounter matches the character assigned. See the official 7th-character definitions and this code’s variants
  2. 4 Use Additional Code instructions — report the named additional code(s) when the documentation supports them. See the Use Additional Code notes
  3. 1 Excludes1 entry — codes named there are generally not reported together with this code (Guidelines I.A.12.a). See the Excludes1 notes

Checklist rows are derived from this code's own official directives; the wording of each check is MedCoder editorial. The official notes themselves are in the sections each row links to.

Verify Before Coding

  • No Medicare Code Editor or MS-DRG Definitions Manual restrictions apply to this code.

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

Other codes that name T58.94XS 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 2 Excludes1 notes across 2 chapters: R09.0 — Asphyxia and hypoxemia (via T58.-), T71 — Asphyxiation (via T58.-).

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

Referenced by 11 Excludes2 notes across 2 chapters: T80 — Complications following infusion, transfusion and therapeutic injection (via T58.-), T80-T88 — Complications of surgical and medical care, not elsewhere classified (T80-T88) (via T58.-), T81 — Complications of procedures, not elsewhere classified (via T58.-), T82 — Complications of cardiac and vascular prosthetic devices, implants and grafts (via T58.-), T83 — Complications of genitourinary prosthetic devices, implants and grafts (via T58.-), T84 — Complications of internal orthopedic prosthetic devices, implants and grafts (via T58.-), T85 — Complications of other internal prosthetic devices, implants and grafts (via T58.-), T86 — Complications of transplanted organs and tissue (via T58.-), T87 — Complications peculiar to reattachment and amputation (via T58.-), T88 — Other complications of surgical and medical care, not elsewhere classified (via T58.-), Z77 — Other contact with and (suspected) exposures hazardous to health (via T58.-).

These codes’ tabular lists name this diagnosis as distinct — both may be reported when both are documented.

Referenced by 68 Code First instructions across 14 chapters: D61.2 — Aplastic anemia due to other external agents (via T58.-), D64.2 — Secondary sideroblastic anemia due to drugs and toxins (via T58.-), E03.2 — Hypothyroidism due to medicaments and other exogenous substances (via T58.-), E09 — Drug or chemical induced diabetes mellitus (via T58.-), F02 — Dementia in other diseases classified elsewhere (via T58.-), G21.2 — Secondary parkinsonism due to other external agents (via T58.-), G62.2 — Polyneuropathy due to other toxic agents (via T58.-), G70.1 — Toxic myoneural disorders (via T58.-), G72.2 — Myopathy due to other toxic agents (via T58.-), G92.8 — Other toxic encephalopathy (via T58.-), G92.9 — Unspecified toxic encephalopathy (via T58.-), H10.21 — Acute toxic conjunctivitis (via T58.-), H35.38 — Toxic maculopathy (via T58.-), H46.3 — Toxic optic neuropathy (via T58.-), H91.0 — Ototoxic hearing loss (via T58.-), I42.7 — Cardiomyopathy due to drug and external agent (via T58.-), J68 — Respiratory conditions due to inhalation of chemicals, gases, fumes and vapors (via T58.-), J69.1 — Pneumonitis due to inhalation of oils and essences (via T58.-), J69.8 — Pneumonitis due to inhalation of other solids and liquids (via T58.-), J70.8 — Respiratory conditions due to other specified external agents (via T58.-), +48 more.

Each of these codes carries a Code First note naming this condition — when that code is reported, THIS code is sequenced first, ahead of it.

MS-DRG Grouper Relationships (FY2026)

Not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity.

Potential MS-DRG participation — not a DRG assignment.

Named in the grouper logic of 2 MS-DRGs: DRG 922 (MDC 21), DRG 923 (MDC 21).

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

Clinical classification (AHRQ CCSR):INJ075 — Poisoning/toxic effect/adverse effects/underdosing, sequela (default).

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 injury, other encounter phase

Same injury, coded at a different phase of treatment via the 7th character.

T58.94XA — Toxic effect of carbon monoxide from unspecified source, undetermined, initial encounterCompare T58.94XS vs T58.94XA →, T58.94XD — Toxic effect of carbon monoxide from unspecified source, undetermined, subsequent encounter

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Poisoning/toxic effect/adverse effects/underdosing, sequela).

+1606 more

Contextual Map

Every relationship of T58.94XS 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 T58.94XS with these 18 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes

  • R09.0 — Asphyxia and hypoxemia[Excludes1](via T58.-): “asphyxia due to carbon monoxide (T58.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
  • T71 — Asphyxiation[Excludes1](via T58.-): “asphyxia from carbon monoxide (T58.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Referenced by Excludes2 notes (11)

Referenced by Code First instructions (68)

Clinical classification (CCSR)

MS-DRG Grouper

MDC crossing

  • MDC 21 — Injuries, Poisonings and Toxic Effects of Drugs[MDC crossing]: “Injuries, Poisonings and Toxic Effects of Drugs — 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. 32,029 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026

Nearest codes (40)

Change history

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

Common coding questions

Does T58.94XS require a 7th character?

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

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

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Toxic effect of carbon monoxide from unspecified source, undetermined, sequela

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 T58.94XS in its code family, with their registry titles.

View all codes in the T58 family