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 New Hampshire, a living will is legally recognized as an Advance Directive for Health Care. This document allows an individual, known as the principal, to outline their preferences for medical treatment in the event that they are unable to communicate their wishes due to a medical emergency. The New Hampshire Advance Directive consists of two parts: a 'Living Will' and a 'Durable Power of Attorney for Health Care.' The Living Will portion specifies the types of life-sustaining treatments that the principal wishes to receive or not receive if they are in a terminal condition or permanently unconscious. The Durable Power of Attorney for Health Care allows the principal to appoint an agent to make health care decisions on their behalf if they are incapacitated. New Hampshire's laws regarding Advance Directives are found in the New Hampshire Revised Statutes Annotated (RSA) under Title XVIII, Section 137-J. It is important for individuals to comply with the specific requirements set forth in these statutes to ensure that their Advance Directive is legally valid and can be enforced by health care providers.