Not every patient visit involves a disease or injury. Sometimes a person comes in for a routine checkup, to receive a vaccine, or simply because they have a family history of cancer and want to be screened. These encounters still require diagnosis codes — and that is exactly what Z-codes are for. Chapter 21 of ICD-10-CM contains the Z-codes (Z00–Z99), and understanding when and how to use them is essential for both the CPC exam and real-world outpatient coding.
What Are Z-Codes?
Z-codes are ICD-10-CM diagnosis codes that describe factors influencing health status and contact with health services — situations that are not classified as diseases or injuries but still explain why a patient is seeking care or provide important context about their health history. They replaced the V-codes used in ICD-9-CM and serve the same general purpose but with far greater specificity.
Z-codes can be used as first-listed diagnoses, as additional diagnoses, or in some cases only as additional diagnoses — never as the primary reason for a visit. Understanding which role a particular Z-code plays is part of mastering their use.
The Six Main Uses of Z-Codes
1. Contact and Exposure to Communicable Disease
Used when a patient has been exposed to a communicable disease but shows no signs of infection. The patient has not yet contracted the disease — the encounter is for evaluation after potential exposure.
Contact with and exposure to communicable diseases
Example: Z20.828 — Contact with and exposure to COVID-19
2. Inoculations and Vaccinations
Used when the sole reason for the encounter is to receive a vaccine. The Z-code is the first-listed diagnosis and the vaccine administration CPT code captures the procedure.
Encounter for immunization
Used as first-listed diagnosis for all vaccination encounters regardless of vaccine type
3. Status Codes
Status codes indicate that a patient has a particular health status — such as having a device implanted, being a carrier of a disease, or having undergone a past procedure that affects current care. Status codes are typically used as additional codes alongside the primary diagnosis.
Long-term use of insulin
Added when a Type 2 diabetic patient uses insulin — one of the most commonly used status codes
Presence of aortocoronary bypass graft
Documents that the patient has had prior CABG surgery — affects ongoing cardiac care decisions
4. History Codes
History codes capture significant past conditions that no longer exist but are relevant to current care. Personal history codes (Z86–Z87) document the patient’s own past conditions. Family history codes (Z80–Z84) document conditions in blood relatives that increase the patient’s own risk.
Personal history of malignant neoplasm of breast
Used after breast cancer has been successfully treated and is no longer active — important for ongoing surveillance coding
Family history of ischemic heart disease and other diseases of the circulatory system
Documents increased cardiovascular risk based on family history — supports medical necessity for preventive screenings
5. Screening Codes
Screening codes are used when a patient with no signs or symptoms undergoes a test to detect a condition before it causes problems. The screening Z-code is the first-listed diagnosis for these encounters.
Encounter for screening for malignant neoplasm of colon
Used for routine colonoscopy screening in patients with no GI symptoms — the screening code, not a symptom, is first-listed
6. Observation and Evaluation
Used when a patient is observed after a suspected condition that is ultimately ruled out. The patient is observed but no disease or injury is confirmed at the end of the encounter.
Encounter for observation for other suspected diseases and conditions ruled out
Used when a patient is evaluated for a suspected condition that is ultimately not confirmed during the encounter
Most Commonly Tested Z-Codes for the CPC Exam
| Z-Code | Description | First-Listed or Additional? |
|---|---|---|
| Z00.00 | Encounter for general adult medical examination without abnormal findings | First-listed |
| Z23 | Encounter for immunization | First-listed |
| Z12.11 | Encounter for screening for colon cancer | First-listed |
| Z79.4 | Long-term use of insulin | Additional only |
| Z79.01 | Long-term use of anticoagulants | Additional only |
| Z87.891 | Personal history of nicotine dependence | Additional only |
| Z85.3 | Personal history of breast cancer | Additional only |
| Z34.– | Encounter for supervision of normal pregnancy | First-listed |
| Z51.11 | Encounter for antineoplastic chemotherapy | First-listed |
| Z96.641 | Presence of right artificial knee joint | Additional only |