2027 ICD-10-CM Diagnosis Code T59.821DToxic effect of hexamethylene diisocyanate, accidental (unintentional), subsequent encounter
T59.821D is a billable ICD-10-CM diagnosis code for toxic effect of hexamethylene diisocyanate, accidental (unintentional), subsequent encounter. The 7th character D marks it as a subsequent encounter code, used during routine care in the healing or recovery phase. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 949 through 950. The code is exempt from POA reporting.
Code Identity
Code Classification
Present on Admission (POA)Billing
T59.821D is exempt from POA reporting on inpatient claims to general acute care hospitals. Review the other POA exempt codes in Toxic effects of substances chiefly nonmedicinal as to source (T51-T65).
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Toxic effect of other gases, fumes and vapors (T59). Use the following options for the applicable episode of care:
- A - initial encounter
- D - subsequent encounter
- S - sequela
Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027, published by CMS and the National Center for Health Statistics.
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to T59.821D: its own notes plus those printed at T59, block T51-T65, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
- chlorofluorocarbons (T53.5)
- contact with and (suspected) exposure to toxic substances (Z77.-)
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
Use Additional Code
Add a second code, after this one, to fully describe the condition.
- code to identify any retained foreign body, if applicable (Z18.-)
Notes
General instructions on how these codes are used.
- 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.
- 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.
7th Character
Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.
- The appropriate 7th character is to be added to each code from category T59
- Ainitial encounter
- Dsubsequent encounter this code
- Ssequela
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name T59.821D, its category, or a range that includes it.
Table of Drugs and ChemicalsClinical
Code History & ChangesHistory
New Code T59.821D was added to the ICD-10-CM code set for FY 2027, effective October 1, 2026.
Replacement T59.821D replaces the following previously assigned code(s):
- T59.891D - Toxic effect of gases, fumes and vapors, accidental, subs
Questions About T59.821DOverview
Is T59.821D a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report toxic effect of hexamethylene diisocyanate, accidental (unintentional), subsequent encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What does the 7th character D in T59.821D mean?
The final character D marks a subsequent encounter: use it for routine care while the toxic effect of hexamethylene diisocyanate, accidental (unintentional) is healing, after active treatment has ended.
What MS-DRG does T59.821D group to?
When toxic effect of hexamethylene diisocyanate, accidental (unintentional), subsequent encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 950, 949, with relative weights from 0.7661 to 1.1231 depending on complications. Higher weights mean higher Medicare reimbursement.
Is T59.821D exempt from POA reporting?
Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for toxic effect of hexamethylene diisocyanate, accidental (unintentional), subsequent encounter on inpatient claims. The code appears in the Toxic effects of substances chiefly nonmedicinal as to source (T51-T65) range of the CMS exempt list.
Can T59.821D be reported with T53.5?
Not as a rule. The Excludes1 note at T59, which applies to T59.821D, lists "chlorofluorocarbons (T53.5)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
