T45.521A – Poisoning by antithrombotic drugs, accidental (unintentional), initial encounter

ICD-10-CM 2027 diagnosis code · Poisoning by, adverse effects of and underdosing of drugs, medicaments and biological substances

Billable code

ICD-10-CM code T45.521A

Code: T45.521A (claims format: T45521A)
Description: Poisoning by antithrombotic drugs, accidental (unintentional), initial encounter
Short description: Poisoning by antithrombotic drugs, accidental, init
Billable: Yes – valid for HIPAA-covered transactions
Valid for: Dates of service October 1, 2026 – September 30, 2027 (FY2027)
Chapter: 19. Injury, poisoning and certain other consequences of external causes (S00-T88)
Block: T36-T50 Poisoning by, adverse effects of and underdosing of drugs, medicaments and biological substances
Parent codes: T45 › T45.5 › T45.52 › T45.521

7th character values

Codes in this category need a 7th character to describe the encounter or episode of care.

Character	Meaning
`A`	initial encounter
`D`	subsequent encounter
`S`	sequela

Notes inherited from parent codes

Instructional notes at a category or block level apply to every code below it.

T45 – Poisoning by, adverse effect of and underdosing of primarily systemic and hematological agents, not elsewhere classified

7th character note:

The appropriate 7th character is to be added to each code from category T45

T45.52 – Poisoning by, adverse effect of and underdosing of antithrombotic drugs

Applicable to:

Poisoning by, adverse effect of and underdosing of antiplatelet drugs

Excludes2 (not included here):

poisoning by, adverse effect of and underdosing of aspirin (T39.01-)
poisoning by, adverse effect of and underdosing of acetylsalicylic acid (T39.01-)

T45.521 – Poisoning by antithrombotic drugs, accidental (unintentional)

Applicable to:

Poisoning by antithrombotic drug NOS

Block T36-T50

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

Excludes1 (not coded here):

toxic reaction to local anesthesia in pregnancy (O29.3-)

Excludes2 (not included here):

abuse and dependence of psychoactive substances (F10-F19)
abuse of non-dependence-producing substances (F55.-)
immunodeficiency due to drugs (D84.821)
drug reaction and poisoning affecting newborn (P00-P96)
pathological drug intoxication (inebriation) (F10-F19)

Code first:

, for adverse effects, the nature of the adverse effect, such as:
adverse effect NOS (T88.7)
aspirin gastritis (K29.-)
blood disorders (D56-D76)
contact dermatitis (L23-L25)
dermatitis due to substances taken internally (L27.-)
nephropathy (N14.0-N14.2)

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)
underdosing of medication regimen (Z91.12-, Z91.13-)

Notes:

The drug giving rise to the adverse effect should be identified by use of codes from categories T36-T50 with fifth or sixth character 5.

Related codes in T45.521

Frequently asked questions

What is ICD-10 code T45.521A?

T45.521A is the ICD-10-CM code for poisoning by antithrombotic drugs, accidental (unintentional), initial encounter, in the block T36-T50 (Poisoning by, adverse effects of and underdosing of drugs, medicaments and biological substances).

Is T45.521A a billable code?

Yes. T45.521A is a billable/specific code that can be used to indicate a diagnosis for reimbursement purposes.

What category does T45.521A belong to?

It belongs to category T45 – Poisoning by, adverse effect of and underdosing of primarily systemic and hematological agents, not elsewhere classified.

Source: CDC/NCHS ICD-10-CM FY2027 code files, tabular list and index. Reference only – code assignment must follow the official ICD-10-CM guidelines and documentation in the medical record.