Unlike infants and young children, adults generally have the ability to make medical decisions for themselves. Because of genetic anomalies, illness, or accidents, some children will never acquire that ability as they grow into adults, and some adults lose the ability during their lifetime. This loss of what is called decision-making capacity or competency in an adult family member may be the result of an accident; an acute medical condition, such as a stroke or heart attack; a terminal illness, such as cancer; or a chronic progressive condition, such as Alzheimer's disease, multiple sclerosis (MS), or amyotrophic lateral sclerosis (ALS, or Lou Gehrig's disease). Generally, if an adult loses decision-making capacity, one or more family members will be asked to make decisions for him or her. That person is commonly called a surrogate (or an agent, representative, or proxy).

Medical decisions for family members literally may be about life or death. However, even when they are not, they can have very serious consequences and may be fraught with anxiety, stress, and uncertainty. Nothing can completely eliminate stress from hard decisions about loved ones. Therefore, the aim of this chapter is modest; it is to provide information that will help you if and when you are called upon to be a surrogate for an adult family member. Hopefully, this information will at least reduce the stress and uncertainty you will experience if you need to make health care decisions for a relative.