2026 ICD-10-CM Diagnosis Code T36.AX6D
Underdosing of fluoroquinolone antibiotics, subsequent encounter
- ICD-10-CM Code:
- T36.AX6D
- ICD-10 Code for:
- Underdosing of fluoroquinolone antibiotics, subs
- Is Billable?
- Yes - Valid for Submission
- Code Navigator:
T36.AX6D is a billable diagnosis code used to specify a medical diagnosis of underdosing of fluoroquinolone antibiotics, subsequent 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. The code is exempt from present on admission (POA) reporting for inpatient admissions to general acute care hospitals.
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.AX6D is a subsequent encounter code, includes a 7th character and should be used after the patient has completed active treatment for a condition like underdosing of fluoroquinolone antibiotics. According to ICD-10-CM Guidelines a "subsequent encounter" occurs when the patient is receiving routine care for the condition during the healing or recovery phase of treatment. Subsequent diagnosis codes are appropriate during the recovery phase, no matter how many times the patient has seen the provider for this condition. If the provider needs to adjust the patient's care plan due to a setback or other complication, the encounter becomes active again.
Coding Guidelines
Underdosing refers to taking less of a medication than is prescribed by a provider or a manufacturer's instruction. Codes for underdosing should never be assigned as principal or first-listed codes. If a patient has a relapse or exacerbation of the medical condition for which the drug is prescribed because of the reduction in dose, then the medical condition itself should be coded.
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.AX6D 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.
Present on Admission (POA)
T36.AX6D is exempt from POA reporting - The Present on Admission (POA) indicator is used for diagnosis codes included in claims involving inpatient admissions to general acute care hospitals. POA indicators must be reported to CMS on each claim to facilitate the grouping of diagnoses codes into the proper Diagnostic Related Groups (DRG). CMS publishes a listing of specific diagnosis codes that are exempt from the POA reporting requirement. Review other POA exempt codes here.
CMS POA Indicator Options and Definitions
POA Indicator: Y
Reason: Diagnosis was present at time of inpatient admission.
CMS Pays CC/MCC DRG? YES
POA Indicator: N
Reason: Diagnosis was not present at time of inpatient admission.
CMS Pays CC/MCC DRG? NO
POA Indicator: U
Reason: Documentation insufficient to determine if the condition was present at the time of inpatient admission.
CMS Pays CC/MCC DRG? NO
POA Indicator: W
Reason: Clinically undetermined - unable to clinically determine whether the condition was present at the time of inpatient admission.
CMS Pays CC/MCC DRG? YES
POA Indicator: 1
Reason: Unreported/Not used - Exempt from POA reporting.
CMS Pays CC/MCC DRG? NO
Replacement Code
T36AX6D replaces the following previously assigned ICD-10-CM code(s):
- T36.8X6D - Underdosing of other systemic antibiotics, subs encntr
Table of Drugs and Chemicals
The parent code T36.AX6 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
