Alphabetic Index FY2027

T58

Toxic effect of carbon monoxide

FY2027Chapter 19: Injury, poisoning and certain other consequences of external causes/T51–T65 Toxic effects of substances chiefly nonmedicinal as to source

Non-billable headerNot valid on its own. Use one of the more specific codes under it.

T58 is a non-billable ICD-10-CM code category for toxic effect of carbon monoxide. Report a more specific code from it instead. It is part of the FY2027 code set, effective October 1, 2026. The more specific codes under it are T58.0 Toxic effect of carbon monoxide from motor vehicle exhaust, T58.1 Toxic effect of carbon monoxide from utility gas, T58.2 Toxic effect of carbon monoxide from incomplete combustion of other domestic fuels, T58.8 Toxic effect of carbon monoxide from other source and 1 more. Its coding notes include a Use additional code instruction, 1 Excludes1 entry and 2 Excludes2 entries.

7th characters

Every code below needs one of these.

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

  • Ainitial encounter
  • Dsubsequent encounter
  • Ssequela

Guidelines tips

From the FY2027 Official Guidelines. ICD10Ref adds no rules of its own.

The 7th character depends on whether the patient is in active treatment, not on who sees the patient. An aftercare Z code is not used for injury aftercare.

Guidelines I.C.19.aInjuries: application of 7th charactersRead the official text

T36-T65 codes already include the substance and the intent, so no additional external cause code is required. Do not code directly from the Table of Drugs and Chemicals.

Guidelines I.C.19.ePoisoning, adverse effects and the Table of DrugsRead the official text

Use additional code

Add the listed code as a secondary code, if known.

Also from chapter/block level (5 notes)
Inherited from T51–T65 Toxic effects of substances chiefly nonmedicinal as to source
  • 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.-)
Inherited from Chapter 19 Injury, poisoning and certain other consequences of external causes
  • code to identify any retained foreign body, if applicable (Z18.-)

Excludes1

Not coded here. The listed conditions generally should not be reported together.

Also from chapter/block level (1 note)
Inherited from T51–T65 Toxic effects of substances chiefly nonmedicinal as to source
  • contact with and (suspected) exposure to toxic substances (Z77.-)

Excludes2

Not included here. Both codes may be reported if the patient has both conditions.

Also from chapter/block level (2 notes)
Inherited from Chapter 19 Injury, poisoning and certain other consequences of external causes
  • birth trauma (P10-P15)
  • obstetric trauma (O70-O71)

Includes

Further defines or gives examples of the content of the category.

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

Notes

Also from chapter/block level (3 notes)
Inherited from T51–T65 Toxic effects of substances chiefly nonmedicinal as to source
  • When no intent is indicated code to accidental. Undetermined intent is only for use when there is specific documentation in the record that the intent of the toxic effect cannot be determined.
Inherited from Chapter 19 Injury, poisoning and certain other consequences of external causes
  • Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
  • The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.

More specific codes under T58 5