Under New York's health care proxy law, any competent person can authorize another person (often a family member) to make health care decisions, if the patient becomes unable to do so.
You do this by completing the standard health care proxy form, noting the person you are designating to make decisions, noting any specific decision that you want the person you are designating to make, and by signing the document in front of two witnesses.
A health care proxy is also different than a living will, although each serves the same purpose of allowing you to make decisions in advance about your health care. A living will is a document that you sign in advance in which you specifically set forth your decisions about health care treatment. Unlike the health care proxy, however, it does not authorize you to appoint an agent to make decisions that you did not anticipate when you completed the living will. The health care proxy provides specific instructions and also designates a person to make decisions when there are events you did not anticipate.
A health care proxy is different than a power of attorney. A power of attorney primarily authorizes the person you designate to make financial decisions for you. It cannot be used to make health care decisions. You must complete a health care proxy in order to have someone be able to make health care decisions when you are not able.
The health care proxy becomes effective only when you become unable to make decisions, as determined by a physician. Until then, you continue to be in charge of making your own health care decisions. It can be revoked orally, and you always have the right while competent to sign a new health care proxy.