T43.591A vs T43.591S

T43.591A (Poisoning by other antipsychotics and neuroleptics, accidental (unintentional), initial encounter) compared with T43.591S (Poisoning by other antipsychotics and neuroleptics, accidental (unintentional), sequela), from the official CMS tabular data. T43.591A and T43.591S code the same injury at a different phase of treatment.

Relationship

Review

Encounter relationship

T43.591A

Initial encounter

Poisoning by other antipsychotics and neuroleptics, accidental (unintentional), initial encounter

↔

T43.591S

Sequela

Poisoning by other antipsychotics and neuroleptics, accidental (unintentional), sequela

Same underlying diagnosis, different encounter phase.

The 7th character records the phase of care for the encounter being coded, so a single encounter takes one of these characters, not several. Review whether both phases belong on the same episode of care.

Source: ICD-10-CM Official Guidelines, Section I.C.19.a

Can these codes be reported together?

Same injury, other encounter phase. T43.591A and T43.591S code the same injury at a different phase of treatment, set by the 7th character.

The 7th character records the type of care given at the encounter being coded (ICD-10-CM Official Guidelines, Section I.C.19.a), so one encounter takes one of these, not both.

Side by side

	T43.591APoisoning by other antipsychotics and neuroleptics, accidental (unintentional), initial encounter	T43.591SPoisoning by other antipsychotics and neuroleptics, accidental (unintentional), sequela
Billing status	Billable	Billable
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 other antipsychotics and neuroleptics, accidental (unintentional), initial encounter is a billable ICD-10-CM diagnosis code (T43.591A).	Poisoning by other antipsychotics and neuroleptics, accidental (unintentional), sequela is a billable ICD-10-CM diagnosis code (T43.591S).
7th character	The appropriate 7th character is to be added to each code from category T43	The appropriate 7th character is to be added to each code from category T43
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