2026 ICD-10-CM Diagnosis Code T36.2X5AAdverse effect of chloramphenicol group, initial encounter

ICD-10-CM Codes›S00–T88›T36-T50›T36

ICD-10-CM T36.2X5A
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

T36.2X5A is a billable ICD-10-CM diagnosis code for adverse effect of chloramphenicol group, 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. The code is not accepted as a principal diagnosis by the Medicare Code Editor. Coders also document this condition as chloramphenicol adverse reaction. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Adverse effects of drugs and medicaments, initial encounter.

Code Identity

ICD-10-CM Code
T36.2X5A
Billable Status
Yes — Valid for Submission
Code Describes
Adverse effect of chloramphenicol group, initial encounter
Short Description
Adverse effect of chloramphenicol group, initial encounter
Same as the full description in the CMS dataset.
Parent Code
T36.2X5
Adverse effect of chloramphenicol group

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 CodeT36.2X5AAdverse effect of chloramphenicol group, initial encounter

Code EditsBilling

Medicare Code Editor checks that affect claim validity for T36.2X5A.

Unacceptable principal diagnosis
There are selected codes that describe a circumstance which influences an individual's health status but not a current illness or injury, or codes that are not specific manifestations but may be due to an underlying cause. These codes are considered unacceptable as a principal diagnosis.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Chloramphenicol adverse reaction
  • Chloramphenicol-induced neutropenia
  • Drug-induced neutropenia
  • Thiamphenicol adverse reaction

Coding GuidelinesGuidance

When coding an adverse effect of a drug that has been correctly prescribed and properly administered, assign the appropriate code for the nature of the adverse effect followed by the appropriate code for the adverse effect of the drug.

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 INJ028
Adverse effects of drugs and medicaments, initial encounter
Default principal diagnosis: inpatient No · 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

Drug Reactions

Most of the time, medicines make our lives better. They reduce aches and pains, fight infections, and control problems such as high blood pressure or diabetes. But medicines can also cause unwanted reactions, such as drug interactions, side effects, and allergies.

The full article covers:

  • What is a drug interaction?
  • What are side effects?
  • What are drug allergies?
  • How can I stay safe when taking medicines?

Read the full article at MedlinePlus

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

Convert T36.2X5A to ICD-9-CMHistory

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

ICD-9-CM
995.29 Adv eff med/biol NEC/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
E930.2 Adv eff chloramphenicol
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 T36.2X5AOverview

Is T36.2X5A (Adverse effect of chloramphenicol group) a billable code?

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

What does the 7th character A in T36.2X5A mean?

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

What MS-DRG does T36.2X5A group to?

On inpatient claims, adverse effect of chloramphenicol group, initial encounter maps to MS-DRG 917, 918, with relative weights from 0.8571 to 1.5684 depending on complications. Higher weights mean higher Medicare reimbursement.

Can T36.2X5A be a principal diagnosis?

No. The Medicare Code Editor rejects this code as a principal diagnosis because adverse effect of chloramphenicol group, initial encounter describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.

What is the ICD-9 equivalent of T36.2X5A?

Under the General Equivalence Mappings, adverse effect of chloramphenicol group, initial encounter converts to ICD-9-CM 995.29 (adv eff med/biol NEC/NOS) and E930.2 (adv eff chloramphenicol). 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.