2026 ICD-10-CM Diagnosis Code T39.1X3APoisoning by 4-Aminophenol derivatives, assault, initial encounter

ICD-10-CM Codes›S00–T88›T36-T50›T39

ICD-10-CM T39.1X3A
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

T39.1X3A is a billable ICD-10-CM diagnosis code for poisoning by 4-Aminophenol derivatives, assault, 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under External cause codes: intent of injury, assault; External cause codes: poisoning by drug; and Poisoning by drugs, initial encounter.

Code Identity

ICD-10-CM Code
T39.1X3A
Billable Status
Yes — Valid for Submission
Code Describes
Poisoning by 4-Aminophenol derivatives, assault, initial encounter
Short Description
Poisoning by 4-Aminophenol derivatives, assault, init encntr
Parent Code
T39.1X3
Poisoning by 4-Aminophenol derivatives, assault

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionT36-T50Poisoning by, adverse effect of and underdosing of drugs, medicaments and biological substances
CategoryT39Poisoning by, adverse effect of and underdosing of nonopioid analgesics, antipyretics and antirheumatics
This CodeT39.1X3APoisoning by 4-Aminophenol derivatives, assault, initial encounter

Coding GuidelinesGuidance

When coding a poisoning or reaction to the improper use of a medication (e.g., overdose, wrong substance given or taken in error, wrong route of administration), first assign the appropriate code from categories T36-T50. The poisoning codes have an associated intent as their 5th or 6th character (accidental, intentional self-harm, assault and undetermined). If the intent of the poisoning is unknown or unspecified, code the intent as accidental intent. The undetermined intent is only for use if the documentation in the record specifies that the intent cannot be determined. Use additional code(s) for all manifestations of poisonings.

The appropriate 7th character is to be added to each code from block Poisoning by, adverse effect of and underdosing of nonopioid analgesics, antipyretics and antirheumatics (T39). 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 EXT022
External cause codes: intent of injury, assault
Default principal diagnosis: inpatient No · outpatient No
CCSR EXT014
External cause codes: poisoning by drug
Default principal diagnosis: inpatient No · outpatient No
CCSR INJ022
Poisoning by drugs, initial encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Acetaminophen

    analgesic antipyretic derivative of acetanilide. it has weak anti-inflammatory properties and is used as a common analgesic, but may cause liver, blood cell, and kidney damage.

  • Arylsulfotransferase

    a sulfotransferase that catalyzes the sulfation of a phenol in the presence of 3'-phosphoadenylylsulfate as sulfate donor to yield an aryl sulfate and adenosine 3',5'-bisphosphate. a number of aromatic compounds can act as acceptors; however, organic hydroxylamines are not substrates. sulfate conjugation by this enzyme is a major pathway for the biotransformation of phenolic and catechol drugs as well as neurotransmitters. ec 2.8.2.1.

  • Cytochrome P-450 CYP1A2

    a cytochrome p450 enzyme subtype that has specificity for relatively planar heteroaromatic small molecules, such as caffeine and acetaminophen.

  • Phenacetin

    a phenylacetamide that was formerly used in analgesics but nephropathy and methemoglobinemia led to its withdrawal from the market. (from smith and reynard, textbook of pharmacology,1991, p431)

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.

SubstanceAccidentalSelf-harmAssaultUndeter­minedAdverse
Effect		Under­dosing
P-AcetamidophenolT39.1X1T39.1X2T39.1X3T39.1X4T39.1X5T39.1X6
AcetaminophenT39.1X1T39.1X2T39.1X3T39.1X4T39.1X5T39.1X6
AcetaminosalolT39.1X1T39.1X2T39.1X3T39.1X4T39.1X5T39.1X6
AcetanilideT39.1X1T39.1X2T39.1X3T39.1X4T39.1X5T39.1X6
AcetophenetedinT39.1X1T39.1X2T39.1X3T39.1X4T39.1X5T39.1X6
4-Aminophenol derivativesT39.1X1T39.1X2T39.1X3T39.1X4T39.1X5T39.1X6
Bromo-seltzerT39.1X1T39.1X2T39.1X3T39.1X4T39.1X5T39.1X6
ExalginT39.1X1T39.1X2T39.1X3T39.1X4T39.1X5T39.1X6
PanadolT39.1X1T39.1X2T39.1X3T39.1X4T39.1X5T39.1X6
Para-acetamidophenolT39.1X1T39.1X2T39.1X3T39.1X4T39.1X5T39.1X6
Para-aminophenol derivativesT39.1X1T39.1X2T39.1X3T39.1X4T39.1X5T39.1X6
ParacetamolT39.1X1T39.1X2T39.1X3T39.1X4T39.1X5T39.1X6
PhenacetinT39.1X1T39.1X2T39.1X3T39.1X4T39.1X5T39.1X6

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 T39.1X3A to ICD-9-CMHistory

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

ICD-9-CM
965.4 Pois-arom analgesics NEC
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
E962.0 Assault-pois w medic agt
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 T39.1X3AOverview

Is T39.1X3A (Poisoning by 4-Aminophenol derivatives, assault) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report poisoning by 4-Aminophenol derivatives, assault, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character A in T39.1X3A mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for poisoning by 4-Aminophenol derivatives, assault, such as an emergency visit or first evaluation.

What MS-DRG does T39.1X3A group to?

When poisoning by 4-Aminophenol derivatives, assault, 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 T39.1X3A?

Under the General Equivalence Mappings, poisoning by 4-Aminophenol derivatives, assault, initial encounter converts to ICD-9-CM 965.4 (pois-arom analgesics NEC) and E962.0 (assault-pois w medic agt). 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.