Z Codes That May be Principal/First-Listed Diagnosis

Published 02/23/2018

Z codes are for use in any healthcare setting. Z codes may be used as either a first-listed (principal diagnosis code in the inpatient setting) or secondary code, depending on the circumstances of the encounter. Certain Z codes may only be used as first-listed or principal diagnosis. For example, there are three observation Z code categories for use in very limited circumstances.

Z Codes indicate a reason for an encounter and are not procedure codes. A corresponding procedure code must accompany a Z code to describe any procedure performed.  For further information, you may refer to ICD-10-CM Official Guidelines for Coding and Reporting, FY 2018 (PDF, 980 KB).

Z Codes That May be Principal/First-Listed Diagnosis
Z codes are a special group of codes provided in ICD-10-CM for the reporting of factors influencing health status and contact with health services. Z codes are designated as the principal/first listed diagnosis in specific situations such as:

  • To indicate that a person with a resolving disease, injury or chronic condition is being seen for specific aftercare
  • To indicate that a person is seen for the sole purpose of special therapy, such as chemotherapy, immunotherapy and radiation therapy
  • To indicate that a person not currently ill is encountering the health service for a specific reason, such as to act as an organ donor, encounter for medical observation for suspected diseases and conditions ruled out, administrative examinations (pre-employment exam, recruitment to armed forces), plastic and reconstructive surgery following medical procedures or healed injury (breast reconstruction following mastectomy)
  • To indicate the birth status of newborns

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