T45.AX3 vs T45.AX4

T45.AX3 (Poisoning by immune checkpoint inhibitors and immunostimulant drugs, assault) compared with T45.AX4 (Poisoning by immune checkpoint inhibitors and immunostimulant drugs, undetermined), from the official CMS tabular data. T45.AX3 and T45.AX4 code the same substance (Immunostimulant) with a different intent.

Relationship

Informational

Drug table relationship

T45.AX3

Poisoning by immune checkpoint inhibitors and immunostimulant drugs, assault

↔

T45.AX4

Poisoning by immune checkpoint inhibitors and immunostimulant drugs, undetermined

Same substance, different circumstance of exposure.

Same substance — undetermined intent (Immunostimulant)

Accidental poisoning, intentional self-harm, assault, undetermined intent, adverse effect and underdosing are mutually exclusive columns — exactly one applies to a given encounter.

Source: CMS Table of Drugs and Chemicals

Can these codes be reported together?

Same substance, different intent. T45.AX3 and T45.AX4 code the same substance (Immunostimulant) with a different circumstance of exposure.

From the CMS Table of Drugs and Chemicals: accidental poisoning, intentional self-harm, assault, undetermined intent, adverse effect and underdosing are mutually exclusive columns — only one of them applies to a given encounter.

Side by side

	T45.AX3Poisoning by immune checkpoint inhibitors and immunostimulant drugs, assault	T45.AX4Poisoning by immune checkpoint inhibitors and immunostimulant drugs, undetermined
Billing status	Non-billable header	Non-billable header
Classification	S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88)	S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88)
Definition	Poisoning by immune checkpoint inhibitors and immunostimulant drugs, assault is a non-billable ICD-10-CM category code (T45.AX3).	Poisoning by immune checkpoint inhibitors and immunostimulant drugs, undetermined is a non-billable ICD-10-CM category code (T45.AX4).
7th character	The appropriate 7th character is to be added to each code from category T45	The appropriate 7th character is to be added to each code from category T45
Includes	adverse effect of correct substance properly administered poisoning by overdose of substance poisoning by wrong substance given or taken in error underdosing by (inadvertently) (deliberately) taking less substance than prescribed or instructed	adverse effect of correct substance properly administered poisoning by overdose of substance poisoning by wrong substance given or taken in error underdosing by (inadvertently) (deliberately) taking less substance than prescribed or instructed
Use additional code	code(s) to specify: manifestations of poisoning underdosing or failure in dosage during medical and surgical care (Y63.6, Y63.8-Y63.9)	code(s) to specify: manifestations of poisoning underdosing or failure in dosage during medical and surgical care (Y63.6, Y63.8-Y63.9)
Code first	, for adverse effects, the nature of the adverse effect, such as: adverse effect NOS (T88.7)	, for adverse effects, the nature of the adverse effect, such as: adverse effect NOS (T88.7)

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Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources