2026 ICD-10-CM Diagnosis Code T36.2X4APoisoning by chloramphenicol group, undetermined, initial encounter

ICD-10-CM Codes›S00–T88›T36-T50›T36

ICD-10-CM T36.2X4A
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

T36.2X4A is a billable ICD-10-CM diagnosis code for poisoning by chloramphenicol group, 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
T36.2X4A
Billable Status
Yes — Valid for Submission
Code Describes
Poisoning by chloramphenicol group, undetermined, initial encounter
Short Description
Poisoning by chloramphenicol group, undetermined, init
Parent Code
T36.2X4
Poisoning by chloramphenicol group, 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 CodeT36.2X4APoisoning by chloramphenicol group, 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

Clinical InformationClinical

  • Chloramphenicol

    an antibiotic first isolated from cultures of streptomyces venequelae in 1947 but now produced synthetically. it has a relatively simple structure and was the first broad-spectrum antibiotic to be discovered. it acts by interfering with bacterial protein synthesis and is mainly bacteriostatic. (from martindale, the extra pharmacopoeia, 29th ed, p106)

  • Chloramphenicol O-Acetyltransferase

    an enzyme that catalyzes the acetylation of chloramphenicol to yield chloramphenicol 3-acetate. since chloramphenicol 3-acetate does not bind to bacterial ribosomes and is not an inhibitor of peptidyltransferase, the enzyme is responsible for the naturally occurring chloramphenicol resistance in bacteria. the enzyme, for which variants are known, is found in both gram-negative and gram-positive bacteria. ec 2.3.1.28.

  • Chloramphenicol Resistance

    nonsusceptibility of bacteria to the action of chloramphenicol, a potent inhibitor of protein synthesis in the 50s ribosomal subunit where amino acids are added to nascent bacterial polypeptides.

  • Thiamphenicol

    a methylsulfonyl analog of chloramphenicol. it is an antibiotic and immunosuppressive agent.

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
ChloramphenicolT36.2X1T36.2X2T36.2X3T36.2X4T36.2X5T36.2X6
Chloramphenicol::ENT agentT36.2X1T36.2X2T36.2X3T36.2X4T36.2X5T36.2X6
Chloramphenicol::ophthalmic preparationT36.2X1T36.2X2T36.2X3T36.2X4T36.2X5T36.2X6
Chloramphenicol::topical NECT36.2X1T36.2X2T36.2X3T36.2X4T36.2X5T36.2X6
ChloromycetinT36.2X1T36.2X2T36.2X3T36.2X4T36.2X5T36.2X6
Chloromycetin::ENT agentT36.2X1T36.2X2T36.2X3T36.2X4T36.2X5T36.2X6
Chloromycetin::ophthalmic preparationT36.2X1T36.2X2T36.2X3T36.2X4T36.2X5T36.2X6
Chloromycetin::otic solutionT36.2X1T36.2X2T36.2X3T36.2X4T36.2X5T36.2X6
Chloromycetin::topical NECT36.2X1T36.2X2T36.2X3T36.2X4T36.2X5T36.2X6
ClopononeT36.2X1T36.2X2T36.2X3T36.2X4T36.2X5T36.2X6
CloramfenicolT36.2X1T36.2X2T36.2X3T36.2X4T36.2X5T36.2X6
ThiamphenicolT36.2X1T36.2X2T36.2X3T36.2X4T36.2X5T36.2X6

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 T36.2X4A to ICD-9-CMHistory

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

ICD-9-CM
960.2 Poison-chloramphenicol
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 T36.2X4AOverview

Is T36.2X4A (Poisoning by chloramphenicol group, undetermined) a billable code?

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

What does the 7th character A in T36.2X4A mean?

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

What MS-DRG does T36.2X4A group to?

When poisoning by chloramphenicol group, 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 T36.2X4A?

Under the General Equivalence Mappings, poisoning by chloramphenicol group, undetermined, initial encounter converts to ICD-9-CM 960.2 (poison-chloramphenicol) 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.