2027 ICD-10-CM Diagnosis Code T45.1X5AAdverse effect of antineoplastic and immunosuppressive drugs, initial encounter
T45.1X5A is a billable ICD-10-CM diagnosis code for adverse effect of antineoplastic and immunosuppressive drugs, 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 791, 793, 917 through 918. The code is not accepted as a principal diagnosis by the Medicare Code Editor. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Adverse effects of drugs and medicaments, initial encounter.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for T45.1X5A.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Accelerated rheumatoid nodulosis
- Accelerated rheumatoid nodulosis caused by methotrexate
- Aclarubicin adverse reaction
- Acquired pancytopenia
- Acral erythema due to cytotoxic therapy
- Acute promyelocytic leukemia, FAB M3
- Adverse reaction to antineoplastic antibiotics
- Adverse reaction to dimethyl sulfoxide and/or idoxuridine
- Adverse reaction to rituximab administered by infusion
- Adverse reaction to sarilumab
- Adverse reaction to trastuzumab administered by infusion
- Adverse reaction to triazene
- Agranulocytosis
- Agranulocytosis due to and following administration of antineoplastic agent
- Aldesleukin adverse reaction
- Alkylating drug adverse reaction
- Amifostine adverse reaction
- Amsacrine adverse reaction
- Anemia caused by antineoplastic agent
- Antimetabolite adverse reaction
- Antineoplastic adverse reaction
- Aplastic anemia caused by antineoplastic agent
- Aplastic anemia due to drugs
- Azathioprine adverse reaction
- Azoospermia caused by chemotherapy
- Bleomycin adverse reaction
- Busulfan adverse reaction
- Carboplatin adverse reaction
- Cardiomyopathy caused by drug
- Carmustine adverse reaction
- Cellular atypia caused by antineoplastic agent
- Chlorambucil adverse reaction
- Chlormethine adverse reaction
- Chronic cyclosporin A nephrotoxicity
- Chronic drug-induced renal disease
- Chronic painful polyneuropathy
- Chronic painful polyneuropathy following chemotherapy
- Chronic peripheral neuropathic pain
- Cirrhosis of liver caused by methotrexate
- Cisplatin adverse reaction
- Complication of chemotherapy
- Crisantaspase adverse reaction
- Cyclophosphamide adverse reaction
- Cyclosporin adverse reaction
- Cytarabine adverse reaction
- Cytotoxic antibiotic adverse reaction
- Dacarbazine adverse reaction
- Dactinomycin adverse reaction
- Dermatosis caused by immunosuppressant
- Dermatosis due to cytotoxic therapy
- Differentiation syndrome due to and following chemotherapy co-occurrent with acute promyelocytic leukemia
- Dilated cardiomyopathy caused by anthracycline
- Dilated cardiomyopathy caused by drug
- Dimethyl sulfoxide adverse reaction
- Disorder of kidney caused by cisplatin
- Disorder of skin caused by epidermal growth factor receptor inhibitor
- Doxorubicin adverse reaction
- Drug-induced cirrhosis of liver
- Drug-induced immunodeficiency
- Drug-induced tubulointerstitial nephritis
- Epirubicin adverse reaction
- Esophagitis due to chemotherapy
- Estramustine adverse reaction
- Ethoglucid adverse reaction
- Etoposide adverse reaction
- Fatigue due to chemotherapy
- Fludarabine adverse reaction
- Fluorouracil adverse reaction
- Gonad regulating hormone adverse reaction
- Goserelin adverse reaction
- Growing teratoma syndrome
- Heart failure following administration of antineoplastic agent
- Hematologic complication of procedure
- Hydroxycarbamide adverse reaction
- Iatrogenic immunodeficiency-associated lymphoproliferative disorder
- Idarubicin adverse reaction
- Ifosfamide adverse reaction
- Immune system complication of procedure
- Immunodeficiency caused by long term therapeutic use of drug
- Immunodeficiency caused by long term therapeutic use of immunosuppressant
- Immunodeficiency secondary to chemotherapy
- Immunosuppressant adverse reaction
- Inflammation of mucous membrane due to and following chemotherapy
- Leuprorelin adverse reaction
- Lomustine adverse reaction
- Lymphoproliferative disorder caused by methotrexate
- Malignant neoplasm after immunosuppressive therapy
- Melphalan adverse reaction
- Mercaptopurine adverse reaction
- Methotrexate adverse reaction
- Methotrexate poisoning
- Methyl CCNU nephropathy
- Mitobronitol adverse reaction
- Mitomycin adverse reaction
- Mitoxantrone adverse reaction
- Myelopathy post intrathecal injection of chemotherapeutic agent
- Myelosuppression
- Myelosuppression due to chemotherapy
- Nephritis caused by drug
- Nephropathy induced by cyclosporine
- Nephropathy induced by tacrolimus
- Neurological pain disorder
- Neurotoxicity caused by L-asparaginase
- Neurotoxicity caused by methotrexate
- Neurotoxicity caused by procarbazine
- Neurotoxicity caused by vinblastine
- Neurotoxicity caused by vincristine
- Nitrogen mustard derivative adverse reaction
- Nitrosurea adverse reaction
- Paclitaxel adverse reaction
- Palmar erythema
- Pancytopenia caused by immunosuppressant
- Pancytopenia caused by medication
- Pentostatin adverse reaction
- Peripheral neuropathic pain
- Peripheral neuropathy due to and following antineoplastic therapy
- Plicamycin adverse reaction
- Poisoning by L-asparaginase
- Post-immunosuppression viral warts
- Procarbazine adverse reaction
- Procarbazine poisoning
- Razoxane adverse reaction
- Retinoid adverse reaction
- Ruxolitinib withdrawal
- Stomatitis due to cytotoxic therapy
- Stomatitis medicamentosa
- Terpenes adverse reaction
- Therapy related acute myeloid leukemia due to and following administration of antineoplastic agent
- Therapy-related myelodysplastic syndrome
- Thioguanine adverse reaction
- Thiotepa adverse reaction
- Thrombophilia due to antineoplastic agent therapy
- Toxic cardiomyopathy
- Toxic dilated cardiomyopathy
- Treosulfan adverse reaction
- Triptorelin adverse reaction
- Ulcer of skin caused by methotrexate
- Ulcerative inflammation of oral mucous membrane due to and following administration of antineoplastic agent
- Ulcerative stomatitis
- Vinblastine adverse reaction
- Vinblastine poisoning
- Vinca alkaloid adverse reaction
- Vincristine adverse reaction
- Vincristine poisoning
- Vindesine adverse reaction
- Warts in immune-deficient state
Coding GuidelinesGuidance
When coding an adverse effect of a drug that has been correctly prescribed and properly administered, assign the appropriate code for the nature of the adverse effect followed by the appropriate code for the adverse effect of the drug.
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 T45.1X5A: 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 T45.1X5A, its category, or a range that includes it.
Excludes1 3
These codes carry an Excludes1 note naming T45.1X5A: 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
Use Additional Code 4
These codes say to use an additional code from the note, and T45.1X5A is one of the codes named.
- D70.1 Agranulocytosis secondary to cancer chemotherapycode for adverse effect, if applicable, to identify drug (T45.1X5) names T45.1X5, which includes this code
- D75.81 Myelofibrosiscode for adverse effect, if applicable, to identify drug (T45.1X5) names T45.1X5, which includes this code
- E88.3 Tumor lysis syndromecode for adverse effect, if applicable, to identify drug (T45.1X5) names T45.1X5, which includes this code
- K12.31 Oral mucositis (ulcerative) due to antineoplastic therapycode for adverse effect, if applicable, to identify antineoplastic and immunosuppressive drugs (T45.1X5) names T45.1X5, which includes this code
Code Also 3
These codes say T45.1X5A 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
Drug Reactions
Most of the time, medicines make our lives better. They reduce aches and pains, fight infections, and control problems such as high blood pressure or diabetes. But medicines can also cause unwanted reactions, such as drug interactions, side effects, and allergies.
The full article covers:
- What is a drug interaction?
- What are side effects?
- What are drug allergies?
- How can I stay safe when taking medicines?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T45.1X5A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T45.1X5AOverview
Is T45.1X5A (Adverse effect of antineoplastic and immunosuppressive drugs) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report adverse effect of antineoplastic and immunosuppressive drugs, initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What does the 7th character A in T45.1X5A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for adverse effect of antineoplastic and immunosuppressive drugs, such as an emergency visit or first evaluation.
What MS-DRG does T45.1X5A group to?
On inpatient claims, adverse effect of antineoplastic and immunosuppressive drugs, initial encounter maps to MS-DRG 793, 791, 918, 917, with relative weights from 0.8716 to 4.2192 depending on complications. Higher weights mean higher Medicare reimbursement.
Can T45.1X5A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because adverse effect of antineoplastic and immunosuppressive drugs, initial encounter describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.
Can T45.1X5A be reported with T45.A?
Not as a rule. The Excludes1 note at T45.1, which applies to T45.1X5A, 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).
