T36.1X3 vs T36.1X6

T36.1X3 (Poisoning by cephalosporins and other beta-lactam antibiotics, assault) compared with T36.1X6 (Underdosing of cephalosporins and other beta-lactam antibiotics), from the official CMS tabular data. T36.1X3 and T36.1X6 code the same substance (Aztreonam) with a different intent. MedCoder-derived

Relationship

Informational

Drug table relationship

T36.1X3

Poisoning by cephalosporins and other beta-lactam antibiotics, assault

↔

T36.1X6

Underdosing of cephalosporins and other beta-lactam antibiotics

Same substance, different circumstance of exposure.

Same substance — underdosing (Aztreonam)

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. T36.1X3 and T36.1X6 code the same substance (Aztreonam) with a different circumstance of exposure.

From the CMS/CDC 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

	T36.1X3Poisoning by cephalosporins and other beta-lactam antibiotics, assault	T36.1X6Underdosing of cephalosporins and other beta-lactam antibiotics
Billing status	Non-billable header Report instead: T36.1X3A, T36.1X3D, T36.1X3S	Non-billable header Report instead: T36.1X6A, T36.1X6D, T36.1X6S
Classification	S00-T88 — Injury, poisoning and certain other consequences of external causes	S00-T88 — Injury, poisoning and certain other consequences of external causes
Definition	Poisoning by cephalosporins and other beta-lactam antibiotics, assault is a non-billable ICD-10-CM category code (T36.1X3).	Underdosing of cephalosporins and other beta-lactam antibiotics is a non-billable ICD-10-CM category code (T36.1X6).
7th character	The appropriate 7th character is to be added to each code from category T36	The appropriate 7th character is to be added to each code from category T36
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