A living will, also sometimes called an "advance health care directive," is a document that says what treatments you do or do not want if you become unable to make or express these choices in the future.
In Ontario, health care providers, such as doctors, cannot take directions from a living will or advance directive. If you become mentally incapable of making health care or personal care decisions yourself, doctors and others must get consent from your "substitute decision-maker" (SDM). While you are still mentally capable, you can choose who your SDM will be by naming them in a special document called a Power of Attorney for Personal Care.
Your SDM must follow any wishes that you expressed while you were mentally capable. So you can include these wishes in your Power of Attorney for Personal Care or other document, or you can express them in some other way.
You can also find information on this topic in CLEO's Every resident: Bill of Rights for people who live in Ontario long-term care homes.