2027 ICD-10-CM Diagnosis Code T45.1X1APoisoning by antineoplastic and immunosuppressive drugs, accidental (unintentional), initial encounter
T45.1X1A is a billable ICD-10-CM diagnosis code for poisoning by antineoplastic and immunosuppressive drugs, accidental (unintentional), initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 917 through 918. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under External cause codes: intent of injury, accidental/unintentional; External cause codes: poisoning by drug; and Poisoning by drugs, initial encounter.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Accidental aclarubicin overdose
- Accidental aclarubicin poisoning
- Accidental aminoglutethimide overdose
- Accidental aminoglutethimide poisoning
- Accidental amsacrine overdose
- Accidental amsacrine poisoning
- Accidental azathioprine overdose
- Accidental azathioprine poisoning
- Accidental bleomycin overdose
- Accidental bleomycin poisoning
- Accidental busulfan overdose
- Accidental busulfan poisoning
- Accidental carboplatin overdose
- Accidental carboplatin poisoning
- Accidental carmustine overdose
- Accidental carmustine poisoning
- Accidental chlorambucil overdose
- Accidental chlorambucil poisoning
- Accidental chlormethine overdose
- Accidental chlormethine poisoning
- Accidental cisplatin overdose
- Accidental cisplatin poisoning
- Accidental crisantaspase overdose
- Accidental crisantaspase poisoning
- Accidental cyclophosphamide overdose
- Accidental cyclophosphamide poisoning
- Accidental cyclosporin overdose
- Accidental cyclosporin poisoning
- Accidental cytarabine overdose
- Accidental cytarabine poisoning
- Accidental dacarbazine overdose
- Accidental dacarbazine poisoning
- Accidental dactinomycin overdose
- Accidental dactinomycin poisoning
- Accidental daunorubicin poisoning
- Accidental doxorubicin overdose
- Accidental doxorubicin poisoning
- Accidental epirubicin overdose
- Accidental epirubicin poisoning
- Accidental estramustine overdose
- Accidental estramustine poisoning
- Accidental ethoglucid overdose
- Accidental ethoglucid poisoning
- Accidental etoposide overdose
- Accidental etoposide poisoning
- Accidental fludarabine overdose
- Accidental fludarabine poisoning
- Accidental fluorouracil overdose
- Accidental fluorouracil poisoning
- Accidental formestane poisoning
- Accidental hydroxycarbamide overdose
- Accidental hydroxycarbamide poisoning
- Accidental idarubicin overdose
- Accidental idarubicin poisoning
- Accidental ifosfamide overdose
- Accidental ifosfamide poisoning
- Accidental lomustine overdose
- Accidental lomustine poisoning
- Accidental melphalan overdose
- Accidental melphalan poisoning
- Accidental mercaptopurine overdose
- Accidental mercaptopurine poisoning
- Accidental methotrexate overdose
- Accidental methotrexate poisoning
- Accidental mitobronitol overdose
- Accidental mitobronitol poisoning
- Accidental mitomycin overdose
- Accidental mitomycin poisoning
- Accidental mitoxantrone overdose
- Accidental mitoxantrone poisoning
- Accidental paclitaxel overdose
- Accidental paclitaxel poisoning
- Accidental pentostatin overdose
- Accidental pentostatin poisoning
- Accidental plicamycin overdose
- Accidental plicamycin poisoning
- Accidental poisoning by carbamates
- Accidental poisoning by carbamic ester
- Accidental poisoning caused by corticosteroid and/or corticosteroid derivative
- Accidental procarbazine overdose
- Accidental procarbazine poisoning
- Accidental razoxane overdose
- Accidental razoxane poisoning
- Accidental thioguanine overdose
- Accidental thioguanine poisoning
- Accidental thiotepa overdose
- Accidental thio-TEPA poisoning
- Accidental treosulfan overdose
- Accidental treosulfan poisoning
- Accidental vinblastine overdose
- Accidental vinblastine poisoning
- Accidental vincristine overdose
- Accidental vincristine poisoning
- Accidental vindesine overdose
- Accidental vindesine poisoning
- Aclarubicin overdose
- Aclarubicin poisoning
- Alkylating drug overdose
- Aminoglutethimide overdose
- Aminoglutethimide poisoning
- Amsacrine overdose
- Amsacrine poisoning
- Antimetabolite overdose
- Antineoplastic overdose
- Azathioprine overdose
- Bleomycin overdose
- Busulfan overdose
- Calcineurin inhibitor poisoning
- Capecitabine overdose
- Carbamate overdose
- Carboplatin overdose
- Carboplatin poisoning
- Carmustine overdose
- Carmustine poisoning
- Chemotherapy changed - acute chemotherapy toxicity
- Chlorambucil overdose
- Chlormethine overdose
- Chlormethine poisoning
- Chronic disease - treatment changed
- Cisplatin overdose
- Cisplatin poisoning
- Crisantaspase overdose
- Crisantaspase poisoning
- Cyclophosphamide overdose
- Cyclosporin overdose
- Cyclosporin poisoning
- Cytarabine overdose
- Cytotoxic antibiotic overdose
- Dacarbazine overdose
- Dacarbazine poisoning
- Dactinomycin overdose
- Doxorubicin overdose
- Doxorubicin poisoning
- Enzyme overdose
- Epirubicin overdose
- Epirubicin poisoning
- Estramustine overdose
- Estramustine poisoning
- Ethoglucid overdose
- Ethoglucid poisoning
- Etoposide overdose
- Etoposide poisoning
- Fludarabine overdose
- Fludarabine poisoning
- Fluorouracil overdose
- Formestane poisoning
- Hydroxycarbamide overdose
- Hydroxycarbamide poisoning
- Idarubicin overdose
- Idarubicin poisoning
- Ifosfamide overdose
- Ifosfamide poisoning
- Immunosuppressant overdose
- Lomustine overdose
- Lomustine poisoning
- Melphalan overdose
- Melphalan poisoning
- Mercaptopurine overdose
- Methotrexate overdose
- Methotrexate poisoning
- Mitobronitol overdose
- Mitobronitol poisoning
- Mitomycin overdose
- Mitoxantrone overdose
- Mitoxantrone poisoning
- Nitrogen mustard derivative overdose
- Nitrogen mustard derivative poisoning
- Nitrosurea overdose
- Nitrosurea poisoning
- Paclitaxel overdose
- Paclitaxel poisoning
- Pentostatin overdose
- Pentostatin poisoning
- Plicamycin overdose
- Plicamycin poisoning
- Poisoning by actinomycin
- Poisoning by azathioprine
- Poisoning by bleomycin
- Poisoning by busulfan
- Poisoning by cactinomycin
- Poisoning by chlorambucil
- Poisoning by cyclophosphamide
- Poisoning by cytarabine
- Poisoning by daunorubicin
- Poisoning by fluorouracil
- Poisoning by L-asparaginase
- Poisoning by mercaptopurine
- Poisoning by mitomycin
- Poisoning by thiotepa
- Procarbazine overdose
- Procarbazine poisoning
- Razoxane overdose
- Razoxane poisoning
- Reason for change in planned chemotherapy treatment
- Thalidomide poisoning
- Thioguanine overdose
- Thioguanine poisoning
- Thiotepa overdose
- Toxicity due to chemotherapy
- Treosulfan overdose
- Treosulfan poisoning
- Triazene antineoplastic overdose
- Vinblastine overdose
- Vinblastine poisoning
- Vinca alkaloid overdose
- Vinca alkaloid poisoning
- Vincristine overdose
- Vincristine poisoning
- Vindesine overdose
- Vindesine poisoning
Coding GuidelinesGuidance
When coding a poisoning or reaction to the improper use of a medication (e.g., overdose, wrong substance given or taken in error, wrong route of administration), first assign the appropriate code from categories T36-T50. The poisoning codes have an associated intent as their 5th or 6th character (accidental, intentional self-harm, assault and undetermined). If the intent of the poisoning is unknown or unspecified, code the intent as accidental intent. The undetermined intent is only for use if the documentation in the record specifies that the intent cannot be determined. Use additional code(s) for all manifestations of poisonings.
The appropriate 7th character is to be added to each code from block Poisoning by, adverse effect of and underdosing of primarily systemic and hematological agents, not elsewhere classified (T45). Use the following options for the applicable episode of care:
- A - initial encounter
- D - subsequent encounter
- S - sequela
Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027, published by CMS and the National Center for Health Statistics.
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to T45.1X1A: its own notes plus those printed at T45.1, T45, block T36-T50, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- 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: the excluded code is never reported together with this one, unless the two conditions are unrelated.
- toxic reaction to local anesthesia in pregnancy (O29.3-)
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
Code First
The underlying condition named in the note is sequenced before this code.
Use Additional Code
Add a second code, after this one, to fully describe the condition.
- code to identify any retained foreign body, if applicable (Z18.-)
Notes
General instructions on how these codes are used.
- Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
- The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.
7th Character
Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.
- The appropriate 7th character is to be added to each code from category T45
- Ainitial encounter this code
- Dsubsequent encounter
- Ssequela
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name T45.1X1A, its category, or a range that includes it.
Excludes1 3
These codes carry an Excludes1 note naming T45.1X1A: they are not reported together with it, unless the two conditions are unrelated.
- T36 Poisoning by, adverse effect of and underdosing of systemic antibioticsantineoplastic antibiotics (T45.1-) names T45.1-, which includes this code
- T37.5 Poisoning by, adverse effect of and underdosing of antiviral drugscytarabine (T45.1-) names T45.1-, which includes this code
- T45.A Poisoning by, adverse effect of and underdosing of immune checkpoint inhibitors and immunostimulant drugspoisoning by, adverse effect of and underdosing of antineoplastic and immunosuppressive drug (T45.1) names T45.1, which includes this code
Code Also 3
These codes say T45.1X1A may also be needed to fully describe the condition. The note gives no sequencing direction.
- J34.81 Nasal mucositis (ulcerative)antineoplastic and immunosuppressive drugs (T45.1X-) names T45.1X-, which includes this code
- K92.81 Gastrointestinal mucositis (ulcerative)antineoplastic and immunosuppressive drugs (T45.1X-) names T45.1X-, which includes this code
- N76.81 Mucositis (ulcerative) of vagina and vulvaantineoplastic and immunosuppressive drugs (T45.1X-) names T45.1X-, which includes this code
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Table of Drugs and ChemicalsClinical
Substances in the Table of Drugs and Chemicals that reference this code family. Always confirm in the Tabular List before coding.
Patient EducationClinical
Medication Errors
Medicines treat infectious diseases, prevent problems from chronic diseases, and ease pain. But medicines can also cause harmful reactions if not used correctly. Errors can happen in the hospital, at the health care provider's office, at the pharmacy, or at home. You can help prevent errors by:
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T45.1X1A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T45.1X1AOverview
Is T45.1X1A a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report poisoning by antineoplastic and immunosuppressive drugs, accidental (unintentional), initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What does the 7th character A in T45.1X1A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for poisoning by antineoplastic and immunosuppressive drugs, accidental (unintentional), such as an emergency visit or first evaluation.
What MS-DRG does T45.1X1A group to?
When poisoning by antineoplastic and immunosuppressive drugs, accidental (unintentional), initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 918, 917, with relative weights from 0.8716 to 1.5698 depending on complications. Higher weights mean higher Medicare reimbursement.
Can T45.1X1A be reported with T45.A?
Not as a rule. The Excludes1 note at T45.1, which applies to T45.1X1A, lists "poisoning by, adverse effect of and underdosing of immune checkpoint inhibitors and immunostimulant drugs (T45.A)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
What is the ICD-9 equivalent of T45.1X1A?
Under the General Equivalence Mappings, poisoning by antineoplastic and immunosuppressive drugs, accidental (unintentional), initial encounter converts to ICD-9-CM 963.1 (pois-antineopl/immunosup) and E858.1 (acc poisn-systemic agent). The mapping is approximate, so confirm the match fits the documentation.
