A living will is a written record of the type of medical care you would want in specific circumstances. It can be used to make treatment decisions if you can no longer communicate your wishes because you are incapacitated by a temporary or permanent injury or illness. Living wills usually take effect after your doctor certifies that you are incapacitated and nearing the end of life. If you have appointed a health care proxy, they should use your living will to make medical decisions on your behalf.