ICD-10 Z codes are used to document which of the following?

• A. Current injury or illness
• B. Family history of disease
• C. The reason for encounter related to social determinants of health
• D. Medication allergies

Answer: (C)

Z codes capture factors that influence health status and contact with health services, not the patient’s actual disease or injury. The best fit is documenting the reason for the encounter in the context of social determinants of health, because these codes are specifically used to record how social conditions like housing, employment, or access to resources contribute to why a patient is seeking care. This helps providers document barriers or facilitators to health and care, beyond the medical diagnosis itself. Other options describe conditions or concerns coded differently—for example, illness or injury is captured with diagnostic codes, and medication allergies are recorded with allergy-related codes—so they don’t align with the primary purpose of Z codes.