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  6. 2025 ICD-10-CM Code T45.AX6D

2025 ICD-10-CM Diagnosis Code T45.AX6D

Underdosing of immune checkpoint inhibitors and immunostimulant drugs, subsequent encounter

ICD-10-CM Code:
T45.AX6D
ICD-10 Code for:
Undrdose of immune checkpoint inhibtr/immunostim drugs, subs
Is Billable?
Yes - Valid for Submission
Code Navigator:

T45.AX6D is a billable diagnosis code used to specify a medical diagnosis of underdosing of immune checkpoint inhibitors and immunostimulant drugs, subsequent encounter. The code is valid during the current fiscal year for the submission of HIPAA-covered transactions from October 01, 2024 through September 30, 2025. The code is exempt from present on admission (POA) reporting for inpatient admissions to general acute care hospitals.

T45.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 immune checkpoint inhibitors and immunostimulant drugs. 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.

Code Classification

  • Injury, poisoning and certain other consequences of external causes
    (S00–T88)
    • Poisoning by, adverse effect of and underdosing of drugs, medicaments and biological substances
      (T36-T50)
      • Poisoning by, adverse effect of and underdosing of primarily systemic and hematological agents, not elsewhere classified
        (T45)

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 primarily systemic and hematological agents, not elsewhere classified (T45). Use the following options for the aplicable episode of care:

  • A - initial encounter
  • D - subsequent encounter
  • S - sequela

Present on Admission (POA)

T45.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

T45AX6D replaces the following previously assigned ICD-10-CM code(s):

  • T45.1X6D - Underdosing of antineoplastic and immunosup drugs, subs

Table of Drugs and Chemicals

The parent code T45.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
ImmuneT45.AX1T45.AX2T45.AX3T45.AX4T45.AX5T45.AX6
Immune
  »checkpoint inhibitors
T45.AX1T45.AX2T45.AX3T45.AX4T45.AX5T45.AX6
Immune
  »globulin
T45.AX1T45.AX2T45.AX3T45.AX4T45.AX5T45.AX6
Immune
  »serum globulin
T45.AX1T45.AX2T45.AX3T45.AX4T45.AX5T45.AX6
Immunostimulant drugT45.AX1T45.AX2T45.AX3T45.AX4T45.AX5T45.AX6

Code History