A living will is your protection when and if you become incapable of making or communicating decisions about your health care. When you're incapable of making or communicating the necessary health care decision. In other words, when you have lost the capacity to give informed consent. If you could speak for yourself, you wouldn't need that piece of paper. For health care purposes, a person with capacity would be one who is able to understand the illness, the nature and effect of the proposed treatment, and the risk in accepting or refusing it.
Several states impose restrictions on the use of living wills.
In most states, the statutes say a living will may be used only if the patient is terminal and death is imminent. The intent of these statutes is to preclude using the living will to refuse treatment for a patient who is seriously ill and with no hope of recovery, but not on the brink of death. Thus, a person in an irreversible coma or with advanced Alzheimer's might be given artificial hydration and nutrition even against his or her wishes. Language such as this is clearly not binding. Under the Cruzan decision, you have the right to refuse treatment, through stating your wishes or through your living will, whether you are in a terminal condition or not.