Z51.81
Encounter for therapeutic drug level monitoring
This code does not map to a risk-adjusting HCC in the loaded models.
Coding notes
Excludes 1 never coded together · Excludes 2 may co-exist
holiday relief care (Z75.5)
follow-up examination after treatment (Z08-Z09)
condition requiring care
follow-up examination for medical surveillance after treatment (Z08-Z09)
Categories Z40-Z53 are intended for use to indicate a reason for care. They may be used for patients who have already been treated for a disease or injury, but who are receiving aftercare or prophylactic care, or care to consolidate the treatment, or to deal with a residual state
Z codes represent reasons for encounters. A corresponding procedure code must accompany a Z code if a procedure is performed. Categories Z00-Z99 are provided for occasions when circumstances other than a disease, injury or external cause classifiable to categories A00-Y89 are recorded as 'diagnoses' or 'problems'. This can arise in two main ways: (a) When a person who may or may not be sick encounters the health services for some specific purpose, such as to receive limited care or service for a current condition, to donate an organ or tissue, to receive prophylactic vaccination (immunization), or to discuss a problem which is in itself not a disease or injury. (b) When some circumstance or problem is present which influences the person's health status but is not in itself a current illness or injury.
Official Guidelines for Z51.81
FY 2026 ›Sections that reference Z51.81
- I.C.2.aAdmission/Encounter for treatment of primary siteChapter 2
… In that case, assign the appropriate Z51.-- code as the first-listed or principal diagnosis, and the underlying diagnosis or problem for which the service is being …
- I.C.2.e.2)Patient admission/encounter chiefly for administration of antineoplastic chemotherapy, immunotherapy and radiation therapyChapter 2
… 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 …
- I.C.2.e.3)Patient admitted for radiation therapy, chemotherapy or immunotherapy and develops complicationsChapter 2
… 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 …
- I.C.21.c.7)Aftercare
… Z47 Orthopedic aftercare Z48 Encounter for other postprocedural aftercare Z49 Encounter for care involving renal dialysis Z51 Encounter for other aftercare and medical care
- I.C.21.c.15)Z Codes That May Only be Principal/First-Listed Diagnosis
… 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 …
- I.B.3Code or codes from A00.0 through T88.9, Z00-Z99.8, U00-U85Conventions & general rules
The appropriate code or codes from A00.0 through T88.9, Z00-Z99.8, and U00-U85 must be used to identify diagnoses, symptoms, conditions, problems, complaints or other reason(s) for the …
Showing 6 of 9. Search the guidelines for Z51. Sections whose FY 2026 text names Z51.81, its Z51 category, or a range containing it — the chapter guidance above is the authoritative source.
Find Z51.81 in the alphabetic index
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