In simple words: This code is used when a doctor needs to record a patient's history of a past illness that isn't the main reason for their visit today.It helps the doctor keep a complete record of the patient's health.

This code captures a patient's personal history of diseases not otherwise specified in other ICD-10-CM categories.It's used when a patient's past medical history includes conditions that might influence their current health status but aren't the reason for the current encounter.This code is supplementary and should be used in conjunction with a code describing the reason for the current visit.If a follow-up examination is the reason for the visit, code Z09 should be sequenced first.

Example 1: A patient presents for an annual physical.During the history, the physician notes a past history of chickenpox (Z86.1).The current encounter is for a routine exam, coded appropriately. Z86.1 is added to document the past infection., A patient with a history of asthma (Z86.0) presents to the emergency room with acute bronchitis. The primary diagnosis is bronchitis, but Z86.0 is added to provide context of a pre-existing respiratory condition. , A patient is seen for a routine gynecological exam. During the history, it is noted that the patient has a personal history of uterine fibroids that were treated surgically in the past. Z86.0 is coded in conjunction with the code for the current exam.

Complete and accurate patient history, including dates of diagnoses and treatment for past illnesses.Clinical notes should clearly state the reason for the current encounter to differentiate from the past illnesses listed in Z86.

** Z86 is a supplementary code and should never be the primary diagnosis unless the patient is specifically seeking care related to a past illness.Always ensure the documentation clearly supports the selection of this code.Specific subcategories within Z86 should be utilized when appropriate for increased specificity.