Z51.12 Encounter for antineoplastic immunotherapy

The ICD-10-CM code for Encounter for antineoplastic immunotherapy is Z51.12 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Chapter

21: Factors influencing health status and contact with health services (Z00-Z99)

Section

Z40-Z53: Encounters for other specific health care (Z40-Z53)

Category Z51

11 codes (8 billable)

FY2026 Status

Stable since FY2024

Also Known As

ICD-10-CM Alphabetic Index entries that lead to Z51.12:

• Encounter (with health service) (for) › immunotherapy for neoplasm
• Immunotherapy (encounter for) › antineoplastic

U.S. Hospital Utilization

• An estimated 10,295 U.S. inpatient stays in 2023 included Z51.12 among the documented diagnoses.
• 7,870 stays listed it as the principal diagnosis.

Source: National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality, 2016–2023. National survey-weighted estimates.

Official Coding Guidelines

Chiefly for antineoplastic chemo/immunotherapy/radiation therapy

2) Patient admission/encounter chiefly for administration of antineoplastic chemotherapy, immunotherapy and radiation therapy If a patient admission/encounter is chiefly for the administration of chemotherapy, immunotherapy or external beam radiation therapy for the treatment of a neoplasm, assign code Z51.0, Encounter for antineoplastic radiation therapy, or Z51.11, Encounter for antineoplastic chemotherapy, or Z51.12, Encounter for antineoplastic immunotherapy as the first-listed or principal diagnosis. If the reason for the encounter is more than one type of antineoplastic therapy, code Z51.0 and codes from subcategory Z51.1 may be assigned together, in which case one of these codes would be reported as a secondary diagnosis. The malignancy for which the therapy is being administered should be assigned as a secondary diagnosis. If a patient admission/encounter is for the insertion or implantation of radioactive elements (e.g., brachytherapy) the appropriate code for the malignancy is sequenced as the principal or first-listed diagnosis. Code Z51.0 should not be assigned.

Complications during admission for chemo/immunotherapy/radiotherapy

3) Patient admitted for radiation therapy, chemotherapy or immunotherapy and develops complications When a patient is admitted for the purpose of external beam radiotherapy, immunotherapy or chemotherapy and develops complications such as uncontrolled nausea and vomiting or dehydration, the principal or first-listed diagnosis is Z51.0, Encounter for antineoplastic radiation therapy, or Z51.11, Encounter for antineoplastic chemotherapy, or Z51.12, Encounter for antineoplastic immunotherapy followed by any codes for the complications.

Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026

References

• CMS — ICD-10-CM Official Code Set and Guidelines, FY2026
• CDC/NCHS — ICD-10-CM Files and Browser Tool
• AHRQ — HCUP National Inpatient Sample, Frequencies by Diagnosis Code (2016–2023)