2026 ICD-10-CM Diagnosis Code T59.5X3SToxic effect of fluorine gas and hydrogen fluoride, assault, sequela
T59.5X3S is a billable ICD-10-CM diagnosis code for toxic effect of fluorine gas and hydrogen fluoride, assault, 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 2026 (October 1, 2025 through September 30, 2026) 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
T59.5X3S is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.
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 2026, published by CMS and the National Center for Health Statistics.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Table of Drugs and ChemicalsClinical
Patient EducationClinical
Poisoning
A poison is any substance that is harmful to your body. You might swallow it, inhale it, inject it, or absorb it through your skin. Any substance can be poisonous if too much is taken. Poisons can include:
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T59.5X3S to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T59.5X3SOverview
Is T59.5X3S (Toxic effect of fluorine gas and hydrogen fluoride, assault) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report toxic effect of fluorine gas and hydrogen fluoride, assault, sequela on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character S in T59.5X3S mean?
The final character S makes this a sequela code: it reports a lingering problem that remains after the toxic effect of fluorine gas and hydrogen fluoride, assault itself has resolved, not the original event.
What MS-DRG does T59.5X3S group to?
When toxic effect of fluorine gas and hydrogen fluoride, assault, sequela is the principal diagnosis on an inpatient stay, it groups to MS-DRG 922, 923, with relative weights from 1.0177 to 1.7494 depending on complications. Higher weights mean higher Medicare reimbursement.
Is T59.5X3S 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 fluorine gas and hydrogen fluoride, assault, sequela on inpatient claims.
What is the ICD-9 equivalent of T59.5X3S?
Under the General Equivalence Mappings, toxic effect of fluorine gas and hydrogen fluoride, assault, sequela converts to ICD-9-CM 909.1 (late eff nonmed substanc). The mapping is approximate, so confirm the match fits the documentation.
Footnotes
[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.
