T45.1 – Poisoning by, adverse effect of and underdosing of antineoplastic and immunosuppressive drugs

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

Non-billable header

ICD-10-CM code T45.1

Code: T45.1 (claims format: T451)
Description: Poisoning by, adverse effect of and underdosing of antineoplastic and immunosuppressive drugs
Short description: Antineoplastic and immunosuppressive drugs
Billable: No – use a more specific code below
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

Billable codes under T45.1

T45.1 is a header code and cannot be used on claims. Choose the most specific code:

T45.1X – Poisoning by, adverse effect of and underdosing of antineoplastic and immunosuppressive drugsHeader (more codes below)

7th character values

Codes in this category need a 7th character to describe the encounter or episode of care (use placeholder X for empty positions).

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

Notes for T45.1

Excludes1 (not coded here):

poisoning by, adverse effect of and underdosing of immune checkpoint inhibitors and immunostimulant drugs (T45.A)
poisoning by, adverse effect of and underdosing of tamoxifen (T38.6)

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

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

Frequently asked questions

What is ICD-10 code T45.1?

T45.1 is the ICD-10-CM code for poisoning by, adverse effect of and underdosing of antineoplastic and immunosuppressive drugs, in the block T36-T50 (Poisoning by, adverse effects of and underdosing of drugs, medicaments and biological substances).

Is T45.1 a billable code?

No. T45.1 is a header code with more specific child codes; report one of the billable codes listed above.

What category does T45.1 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.