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 Illinois, a living will is recognized under the Illinois Living Will Act (755 ILCS 35/). This document allows an individual, known as the declarant, to express their wishes regarding medical treatment in the event they are unable to communicate due to a terminal condition. The living will can specify whether the declarant wants life-sustaining treatments to be administered, withheld, or withdrawn if they are diagnosed with a terminal condition and if death is imminent. The living will must be signed by the declarant and witnessed by two individuals who are not beneficiaries of the declarant's estate. Illinois also recognizes other advance directives such as the Power of Attorney for Health Care, which allows an individual to appoint an agent to make health care decisions on their behalf, and Do Not Resuscitate (DNR) orders, which instruct medical personnel not to perform CPR if the patient's breathing or heart stops. It's important for individuals to ensure that their living will and other advance directives comply with Illinois law to be legally effective.