2026 ICD-10-CM Diagnosis Code T36.94XAPoisoning by unspecified systemic antibiotic, undetermined, initial encounter

ICD-10-CM Codes›S00–T88›T36-T50›T36

ICD-10-CM T36.94XA
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

T36.94XA is a billable ICD-10-CM diagnosis code for poisoning by unspecified systemic antibiotic, undetermined, 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, undetermined; External cause codes: poisoning by drug; and Poisoning by drugs, initial encounter.

Code Identity

ICD-10-CM Code
T36.94XA
Billable Status
Yes — Valid for Submission
Code Describes
Poisoning by unspecified systemic antibiotic, undetermined, initial encounter
Short Description
Poisoning by unsp systemic antibiotic, undetermined, init
Parent Code
T36.94
Poisoning by unspecified systemic antibiotic, undetermined

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
CategoryT36Poisoning by, adverse effect of and underdosing of systemic antibiotics
This CodeT36.94XAPoisoning by unspecified systemic antibiotic, undetermined, 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 systemic antibiotics (T36). 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 EXT023
External cause codes: intent of injury, undetermined
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

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
Antibiotic NECT36.91T36.92T36.93T36.94T36.95T36.96
Antibiotic NEC::aminoglycosideT36.91T36.92T36.93T36.94T36.95T36.96
Antibiotic NEC::anticancerT36.91T36.92T36.93T36.94T36.95T36.96
Antibiotic NEC::antifungalT36.91T36.92T36.93T36.94T36.95T36.96
Antibiotic NEC::antimycobacterialT36.91T36.92T36.93T36.94T36.95T36.96
Antibiotic NEC::antineoplasticT36.91T36.92T36.93T36.94T36.95T36.96
Antibiotic NEC::cephalosporin (group)T36.91T36.92T36.93T36.94T36.95T36.96
Antibiotic NEC::chloramphenicol (group)T36.91T36.92T36.93T36.94T36.95T36.96
Antibiotic NEC::ENTT36.91T36.92T36.93T36.94T36.95T36.96
Antibiotic NEC::eyeT36.91T36.92T36.93T36.94T36.95T36.96
Antibiotic NEC::fungicidal (local)T36.91T36.92T36.93T36.94T36.95T36.96
Antibiotic NEC::intestinalT36.91T36.92T36.93T36.94T36.95T36.96
Antibiotic NEC::b-lactam NECT36.91T36.92T36.93T36.94T36.95T36.96
Antibiotic NEC::localT36.91T36.92T36.93T36.94T36.95T36.96
Antibiotic NEC::macrolidesT36.91T36.92T36.93T36.94T36.95T36.96
Antibiotic NEC::polypeptideT36.91T36.92T36.93T36.94T36.95T36.96
Antibiotic NEC::specified NECT36.91T36.92T36.93T36.94T36.95T36.96
Antibiotic NEC::tetracycline (group)T36.91T36.92T36.93T36.94T36.95T36.96
Antibiotic NEC::throatT36.91T36.92T36.93T36.94T36.95T36.96

Patient EducationClinical

Antibiotics

Antibiotics are medicines that fight bacterial infections in people and animals. They work by killing the bacteria or by making it hard for the bacteria to grow and multiply.

The full article covers:

  • What are antibiotics?
  • What do antibiotics treat?
  • Do antibiotics treat viral infections?
  • What are the side effects of antibiotics?
  • Why is it important to take antibiotics only when they're needed?
  • How do I use antibiotics correctly?

Read the full article at MedlinePlus

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

Convert T36.94XA to ICD-9-CMHistory

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

ICD-9-CM
960.9 Poisoning-antibiotic NOS
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
E980.4 Undet pois-med agnt NEC
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 T36.94XAOverview

Is T36.94XA (Poisoning by unspecified systemic antibiotic, undetermined) a billable code?

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

What does the 7th character A in T36.94XA mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for poisoning by unspecified systemic antibiotic, undetermined, such as an emergency visit or first evaluation.

What MS-DRG does T36.94XA group to?

When poisoning by unspecified systemic antibiotic, undetermined, 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 T36.94XA?

Under the General Equivalence Mappings, poisoning by unspecified systemic antibiotic, undetermined, initial encounter converts to ICD-9-CM 960.9 (poisoning-antibiotic NOS) and E980.4 (undet pois-med agnt NEC). 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.