2025 ICD-10-CM Diagnosis Code T45.AX6A
Underdosing of immune checkpoint inhibitors and immunostimulant drugs, initial encounter
- ICD-10-CM Code:
- T45.AX6A
- ICD-10 Code for:
- Undrdose of immune checkpoint inhibtr/immunostim drugs, init
- Is Billable?
- Yes - Valid for Submission
- Code Navigator:
T45.AX6A is a billable diagnosis code used to specify a medical diagnosis of underdosing of immune checkpoint inhibitors and immunostimulant drugs, initial 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.
T45.AX6A is an initial encounter code, includes a 7th character and should be used while the patient is receiving active treatment for a condition like underdosing of immune checkpoint inhibitors and immunostimulant drugs. 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
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
Replacement Code
T45AX6A replaces the following previously assigned ICD-10-CM code(s):
- T45.1X6A - Underdosing of antineoplastic and immunosup drugs, init
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 |
|---|---|---|---|---|---|---|
| Immune | T45.AX1 | T45.AX2 | T45.AX3 | T45.AX4 | T45.AX5 | T45.AX6 |
| Immune »checkpoint inhibitors | T45.AX1 | T45.AX2 | T45.AX3 | T45.AX4 | T45.AX5 | T45.AX6 |
| Immune »globulin | T45.AX1 | T45.AX2 | T45.AX3 | T45.AX4 | T45.AX5 | T45.AX6 |
| Immune »serum globulin | T45.AX1 | T45.AX2 | T45.AX3 | T45.AX4 | T45.AX5 | T45.AX6 |
| Immunostimulant drug | T45.AX1 | T45.AX2 | T45.AX3 | T45.AX4 | T45.AX5 | T45.AX6 |
