The Living Will is a document used to provide instructions directly to a doctor regarding your desires for being placed on life-support. This document allows you to specify what kinds of medical treatment you would wish to accept or reject if you should become irreversibly or terminally ill and are unable at that time to make your wishes known.
Some people would prefer to have this decision made by a family member or loved one, while other people would prefer to leave the decision to a doctor rather than putting a family member through the emotional stress of making such a difficult decision.
The creation of a living will is a very personal decision. Some people are strongly in favor of it, while others are opposed. If you have a Medical Power of Attorney, then the agent who you have granted the power has the authority to make the decision whether or not to authorize or deny life support. The Living Will is a directive from a patient to the doctor, the only way that the doctor will know about the Living Will is for the doctor to have been supplied with a copy by you or a family member. Because emergency hospitalizations happen, you should discuss your desires related to life support with your family members and friends so that they can act accordingly in the event of an unforeseen tragedy.