Any complete estate plan should include a medical directive. This term may encompass a number of different documents, including a health care proxy, a durable power of attorney for health care, a living will, and medical instructions. The exact document or documents will depend on your state's laws and the choices you make.
Both a health care proxy and a durable power of attorney for health care designate someone you choose to make health care decisions for you if you are unable to do so yourself. A living will instructs your health care provider to withdraw life support if you are terminally ill or in a vegetative state. A broader medical directive may include the terms of a living will, but will also provide instructions if you are in a less serious state of health, but are still unable to direct your health care yourself.
For more information, see End-of-Life Care Decision Making.