2027 ICD-10-CM Diagnosis Code T57.3X4SToxic effect of hydrogen cyanide, undetermined, sequela
T57.3X4S is a billable ICD-10-CM diagnosis code for toxic effect of hydrogen cyanide, undetermined, sequela. The 7th character S marks it as a sequela code, which reports a problem that remains after the original condition has resolved. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 922 through 923. The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Poisoning/toxic effect/adverse effects/underdosing, sequela.
Code Identity
Code Classification
Present on Admission (POA)Billing
T57.3X4S 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 inorganic substances (T57). 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 T57.3X4S: its own notes plus those printed at T57, 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.
- 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 T57
- Ainitial encounter
- Dsubsequent encounter
- Ssequela this code
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name T57.3X4S, its category, or a range that includes it.
Excludes1 3
These codes carry an Excludes1 note naming T57.3X4S: they are not reported together with it, unless the two conditions are unrelated.
- T61 Toxic effect of noxious substances eaten as seafoodtoxic effect of hydrogen cyanide (T57.3-) names T57.3-, which includes this code
- T62 Toxic effect of other noxious substances eaten as foodtoxic effect of hydrogen cyanide (T57.3-) names T57.3-, which includes this code
- T65.0 Toxic effect of cyanideshydrogen cyanide (T57.3-) names T57.3-, which includes this code
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Hydrogen Cyanide
hydrogen cyanide (hcn); a toxic liquid or colorless gas. it is found in the smoke of various tobacco products and released by combustion of nitrogen-containing organic materials.
Table of Drugs and ChemicalsClinical
Substances in the Table of Drugs and Chemicals that reference this code family. Always confirm in the Tabular List before coding.
| Substance | Accidental | Self-harm | Assault | Undetermined | Adverse Effect | Underdosing |
|---|---|---|---|---|---|---|
| Cyanide (s) (compounds) (potassium) (sodium) NEC::dust or gas (inhalation) NEC | T57.3X1 | T57.3X2 | T57.3X3 | T57.3X4 | – | – |
| Cyanide (s) (compounds) (potassium) (sodium) NEC::hydrogen | T57.3X1 | T57.3X2 | T57.3X3 | T57.3X4 | – | – |
| Gas NEC::cyanide | T57.3X1 | T57.3X2 | T57.3X3 | T57.3X4 | – | – |
| HCN | T57.3X1 | T57.3X2 | T57.3X3 | T57.3X4 | – | – |
| Hexahydrocresol (s)::cyanide | T57.3X1 | T57.3X2 | T57.3X3 | T57.3X4 | – | – |
| Hydrocyanic acid (liquid) | T57.3X1 | T57.3X2 | T57.3X3 | T57.3X4 | – | – |
| Hydrogen::cyanide (salts) | T57.3X1 | T57.3X2 | T57.3X3 | T57.3X4 | – | – |
| Hydrogen::cyanide (salts)::gas | T57.3X1 | T57.3X2 | T57.3X3 | T57.3X4 | – | – |
| Prussic acid::vapor | T57.3X1 | T57.3X2 | T57.3X3 | T57.3X4 | – | – |
Convert T57.3X4S to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T57.3X4SOverview
What is the ICD-10 code for toxic effect of hydrogen cyanide, undetermined, sequela?
The ICD-10-CM code for toxic effect of hydrogen cyanide, undetermined, sequela is T57.3X4S (sometimes written as T573X4S). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is T57.3X4S (Toxic effect of hydrogen cyanide, undetermined) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report toxic effect of hydrogen cyanide, undetermined, sequela on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What does the 7th character S in T57.3X4S mean?
The final character S makes this a sequela code: it reports a lingering problem that remains after the toxic effect of hydrogen cyanide, undetermined itself has resolved, not the original event.
What MS-DRG does T57.3X4S group to?
When toxic effect of hydrogen cyanide, undetermined, sequela is the principal diagnosis on an inpatient stay, it groups to MS-DRG 923, 922, with relative weights from 0.9980 to 1.6248 depending on complications. Higher weights mean higher Medicare reimbursement.
Is T57.3X4S 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 hydrogen cyanide, undetermined, sequela 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.
