T58 ICD-10-CM Code: Toxic effect of carbon monoxide

T58 is the ICD-10-CM diagnosis code for toxic effect of carbon monoxide. T58 sits in the ICD-10-CM chapter for injury, poisoning and certain other consequences of external causes (s00-t88), within the section covering toxic effects of substances chiefly nonmedicinal as to source (t51-t65).

Header codes like T58 cannot be reported on claims directly, they organize child codes that share clinical context but the actual diagnosis must be coded to the highest level of specificity supported by the documentation. Coders should look at T58's child codes and select the one that matches the patient's documented presentation, since payers reject header codes submitted as the primary diagnosis. For risk adjustment workflows, header codes never contribute to a Medicare Advantage member's RAF score on their own; only billable child codes that happen to map to a payment HCC affect risk-adjusted plan payments.