Now she has become a household name after Congress and the president entered the legal battle to prolong her life against her husband's insistence that she would have preferred to die rather than live with severe brain damage.
The documents can go a long way toward helping family members who must make hard choices on behalf of loved ones who are unable to speak for themselves. But even if you've done everything right, it doesn't guarantee that your family won't be embroiled in a nasty court fight.
J. Joseph Hart, chaplain and director of spiritual support services at the Greater Baltimore Medical Center, said he has seen how difficult it is for families without such documents to make decisions in emergencies.
"We are asking them medical questions. 'What do you want us to do? Do you want to keep doing CPR? Is this what your loved one would want? How far do you want us to go?' " Hart said. "It is tortuous for these family members who have never had these conversations."
Most of us have thought about this as an issue for the elderly, but Schiavo, Karen Ann Quinlan and Nancy Cruzan - all high-profile right-to-die cases - were in their 20s when they suffered brain damage. That's why legal experts advise that anyone age 18 or older should have these documents.
The documents are also necessary for unmarried couples who want their partners, rather than a relative, to make medical decisions for them, said Jeff Gonya, an estate planning lawyer in Baltimore.
The documents, and even their names, vary from state to state. Basically, you need two. A health care power of attorney lets you name a person or health care agent who would make medical decisions on your behalf if you became incapacitated. A living will allows you to express what life-prolonging measures you want, or don't want, if you fall into, say, a persistent vegetative state.
In some states, these are two separate documents. In Maryland, they are rolled into one, called an advance directive.
You don't need an attorney to draw up documents, although some suggest that a lawyer can make sure your forms comply with state law if you have questions.
The forms are available from doctors, private and public hospitals and on the Internet. Maryland's attorney general's office explains the advance directive and posts forms online at www.oag.state.md.us/Healthpol/.
Healthcare and Elder Law Programs, a California-based nonprofit, offers a booklet to help people weigh their medical choices and communicate their desires to their health care agents. You can order two free copies - one for you and one for your agent - online at www.better-endings.org or by calling 310-533-1996.
States generally honor one another's advance directives. Delays or problems can occur, however, if patients moved from, say, Maryland to California years ago but never got California documents, said Ed Long, executive director of H.E.L.P.
If you divide your time between two states, fill out documents for both, lawyers recommend.
One of the most important decisions you'll make is the choice of health care agent. This is your medical advocate for end-of-life treatment and for more basic care decisions, such as the choice of doctor.
Choose someone who shares your values and would be able to carry out your wishes.
"Sometimes spouses are not the best persons to be the health care agent ... because they are too emotional," Hart said. You want "someone who could remain objective despite their own personal desires for the patient," he said.
But even with the right documents, there's no guarantee that your wishes will be carried out.