Z51.1 Encounter for antineoplastic chemotherapy and immunotherapy

The ICD-10-CM code for Encounter for antineoplastic chemotherapy and immunotherapy is Z51.1 (FY2026). It is a non-billable category code — select a more specific code below for claims.

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

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.

List of Z codes (partial; preceding guideline context missing)

Z31.81 Encounter for male factor infertility in female patient Z31.83 Encounter for assisted reproductive fertility procedure cycle Z31.84 Encounter for fertility preservation procedure Z34 Encounter for supervision of normal pregnancy Z39 Encounter for maternal postpartum care and examination Z38 Liveborn infants according to place of birth and type of delivery Z40 Encounter for prophylactic surgery Z42 Encounter for plastic and reconstructive surgery following medical procedure or healed injury Z51.0 Encounter for antineoplastic radiation therapy Z51.1- Encounter for antineoplastic chemotherapy and immunotherapy Z52 Donors of organs and tissues Except: Z52.9, Donor of unspecified organ or tissue Z76.1 Encounter for health supervision and care of foundling Z76.2 Encounter for health supervision and care of other healthy infant and child Z99.12 Encounter for respirator [ventilator] dependence during power failure

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