A living will—also known as an Advance Health Care Directive—is a document in which the declarant or principal (person making the living will) specifies what kind of medical treatment the declarant does and does not want if the declarant has a medical emergency and is unable to communicate those wishes. A living will may direct health care providers to administer, withhold, or withdraw life-sustaining treatments if the declarant is in a terminal or irreversible condition.

Laws and terminology for documents related to living wills, Advance Health Care Directives, Do Not Resuscitate orders (DNRs), and other health care documents vary from state to state. These laws are generally located in a state’s statutes—often in the probate code or estates code.

In California, a living will is known as an Advance Health Care Directive (AHCD). The AHCD allows individuals to specify their preferences for medical treatment in the event that they are unable to communicate due to a medical emergency. This includes directions on administering, withholding, or withdrawing life-sustaining treatment if the individual is in a terminal or irreversible condition. The AHCD can also appoint a health care agent to make decisions on the individual's behalf. California's Probate Code sections 4600-4806 specifically govern the creation and use of Advance Health Care Directives. Additionally, Californians can establish Do Not Resuscitate (DNR) orders, which are separate documents instructing health care providers not to perform CPR if the patient's breathing or heartbeat stops. It's important for individuals to ensure that their AHCD and any other health care documents are properly executed according to California law to be legally effective.