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ICD-10-CM 2027 diagnosis code

T59.821Toxic effect of hexamethylene diisocyanate, accidental (unintentional)

Not billable — use a more specific codeNew for 2027Requires 7th character

T59.821 is a header code, so it can't be reported by itself. Choose one of the 3 more specific codes beneath it and add the required 7th character.Short description: Toxic effect of hexamethylene diisocyanate, accidental

Code last changed in FY2027 (effective October 1, 2026). Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About T59.821

T59.821 is the ICD-10-CM diagnosis code for toxic effect of hexamethylene diisocyanate, accidental (unintentional). It belongs to category T59 (toxic effect of other gases, fumes and vapors), block T51-T65 (toxic effects of substances chiefly nonmedicinal as to source) and chapter 19 (injury, poisoning and certain other consequences of external causes). It is a header code, so it can't be reported by itself; one of its 3 subcodes must be used instead.

Within T59.82 (toxic effects of hexamethylene diisocyanate), T59.821 is specifically for toxic effect of hexamethylene diisocyanate, accidental (unintentional). Related codes cover intentional self-harm (T59.822), assault (T59.823) and undetermined (T59.824).

Codes in this range require a 7th character: A for initial encounter, D for subsequent encounter and S for sequela. Use placeholder "X" characters to fill any empty positions before the 7th character.

It was added in FY2027, effective October 1, 2026.

7th character

The appropriate 7th character is to be added to each code from category T59

Coding notes

Applicable toConditions and synonyms classified to this code
  • Toxic effects of hexamethylene diisocyanate NOS

Notes that apply from higher levels

Instructions written at a parent level also apply to T59.821.

› From T59 Toxic effect of other gases, fumes and vapors
Includes
  • aerosol propellants
Excludes1
  • chlorofluorocarbons (T53.5)

Broader instructions also apply from T51-T65 Toxic effects of substances chiefly nonmedicinal as to source and Chapter 19: Injury, poisoning and certain other consequences of external causes.

Table of Drugs & Neoplasms entries

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2027 (effective 10/1/2026): Added

Common questions about T59.821

Is T59.821 billable?

No. T59.821 is a header code. Report one of its more specific subcodes instead.

Did T59.821 change for 2027?

Yes. For FY2027 (effective October 1, 2026) it was added to the code set.