2026 ICD-10-CM Diagnosis Code T63.591AToxic effect of contact with other venomous fish, accidental (unintentional), initial encounter

ICD-10-CM Codes›S00–T88›T51-T65›T63

ICD-10-CM T63.591A
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

T63.591A is a billable ICD-10-CM diagnosis code for toxic effect of contact with other venomous fish, accidental (unintentional), initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 917 through 918. Coders also document this condition as fish sting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under External cause codes: bites; initial encounter; External cause codes: intent of injury, accidental/unintentional; and Toxic effects, initial encounter.

Code Identity

ICD-10-CM Code
T63.591A
Billable Status
Yes — Valid for Submission
Code Describes
Toxic effect of contact with other venomous fish, accidental (unintentional), initial encounter
Short Description
Toxic effect of contact w oth venomous fish, acc, init
Parent Code
T63.591
Toxic effect of contact with other venomous fish, accidental (unintentional)

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionT51-T65Toxic effects of substances chiefly nonmedicinal as to source
CategoryT63Toxic effect of contact with venomous animals and plants
This CodeT63.591AToxic effect of contact with other venomous fish, accidental (unintentional), initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Fish sting
  • Poisoning by venomous fish
  • Poisoning due to sting of lion fish spine
  • Poisoning due to sting of weever fish spine
  • Sting by stone fish spine
  • Sting by weever fish spine

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Toxic effect of contact with venomous animals and plants (T63). 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.

CCSR EXT012
External cause codes: bites; initial encounter
Default principal diagnosis: inpatient No · outpatient No
CCSR EXT020
External cause codes: intent of injury, accidental/unintentional
Default principal diagnosis: inpatient No · outpatient No
CCSR INJ023
Toxic effects, initial encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Animal Bites

Wild animals usually avoid people. They might attack, however, if they feel threatened, are sick, or are protecting their young or territory. Attacks by pets are more common. Animal bites rarely are life-threatening, but if they become infected, you can develop serious medical problems.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert T63.591A to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
989.5 Toxic effect venom
ApproximateCombination The match is approximate, and more than one code can be needed to describe the source diagnosis. Confirm with contextual judgment.
ICD-9-CM
E905.6 Venom sea animals/plants
ApproximateCombination The match is approximate, and more than one code can be needed to describe the source diagnosis. Confirm with contextual judgment.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About T63.591AOverview

Is T63.591A a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report toxic effect of contact with other venomous fish, accidental (unintentional), initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character A in T63.591A mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for toxic effect of contact with other venomous fish, accidental (unintentional), such as an emergency visit or first evaluation.

What MS-DRG does T63.591A group to?

When toxic effect of contact with other venomous fish, accidental (unintentional), initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 917, 918, with relative weights from 0.8571 to 1.5684 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of T63.591A?

Under the General Equivalence Mappings, toxic effect of contact with other venomous fish, accidental (unintentional), initial encounter converts to ICD-9-CM 989.5 (toxic effect venom) and E905.6 (venom sea animals/plants). 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.