2026 ICD-10-CM Diagnosis Code T36.AX5A
Adverse effect of fluoroquinolone antibiotics, initial encounter
- ICD-10-CM Code:
- T36.AX5A
- ICD-10 Code for:
- Adverse effect of fluoroquinolone antibiotics, init
- Is Billable?
- Yes - Valid for Submission
- Code Navigator:
T36.AX5A is a billable diagnosis code used to specify a medical diagnosis of adverse effect of fluoroquinolone antibiotics, initial encounter. The code is valid during the current fiscal year for the submission of HIPAA-covered transactions from October 01, 2025 through September 30, 2026.
This code describes a circumstance which influences the patient's health status but not a current illness or injury. The code is unacceptable as a principal diagnosis.
T36.AX5A is an initial encounter code, includes a 7th character and should be used while the patient is receiving active treatment for a condition like adverse effect of fluoroquinolone antibiotics. According to ICD-10-CM Guidelines an "initial encounter" doesn't necessarily means "initial visit". The 7th character should be used when the patient is undergoing active treatment regardless if new or different providers saw the patient over the course of a treatment. The appropriate 7th character codes should also be used even if the patient delayed seeking treatment for a condition.
Coding Guidelines
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 aplicable episode of care:
- A - initial encounter
- D - subsequent encounter
- S - sequela
New 2026 ICD-10-CM Code
T36.AX5A is new to ICD-10-CM code set for the FY 2026, effective October 1, 2025. The National Center for Health Statistics (NCHS) has published an update to the ICD-10-CM diagnosis codes which became effective October 1, 2025. This is a new and revised code for the FY 2026 (October 1, 2025 - September 30, 2026).
Code Edits
The Medicare Code Editor (MCE) detects errors and inconsistencies in ICD-10-CM diagnosis coding that can affect Medicare claim validity. These Medicare code edits help medical coders and billing professionals determine when a diagnosis code is not appropriate as a principal diagnosis, does not meet coverage criteria. Use this list to verify whether a code is valid for Medicare billing and to avoid claim rejections or denials due to diagnosis coding issues.
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.
Replacement Code
T36AX5A replaces the following previously assigned ICD-10-CM code(s):
- T36.8X5A - Adverse effect of other systemic antibiotics, init encntr
Table of Drugs and Chemicals
The parent code T36.AX5 of the current diagnosis code is referenced in the Table of Drugs and Chemicals, this table contains a classification of drugs, industrial solvents, corrosive gases, noxious plants, pesticides, and other toxic agents.
According to ICD-10-CM coding guidelines it is advised to do not code directly from the Table of Drugs and Chemicals, instead always refer back to the Tabular List when doing the initial coding. Each substance in the table is assigned a code according to the poisoning classification and external causes of adverse effects. It is important to use as many codes as necessary to specify all reported drugs, medicinal or chemical substances. If the same diagnosis code describes the causative agent for more than one adverse reaction, poisoning, toxic effect or underdosing, utilize the code only once.
| Substance | Poisoning Accidental (unintentional) |
Poisoning Accidental (self-harm) |
Poisoning Assault |
Poisoning Undetermined |
Adverse effect |
Underdosing |
|---|---|---|---|---|---|---|
| Fluoroquinolone antibiotics | T36.AX1 | T36.AX2 | T36.AX3 | T36.AX4 | T36.AX5 | T36.AX6 |
Code History
- FY 2026 - Code Added, effective from 10/1/2025 through 9/30/2026
