John B. Whalen Living Wills Law Blog on Lawyers.com

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A common misunderstanding with a Living Will is that your doctor will, or must, follow your directions.  Unfortunately, this is not true.  However, should this not be the case, your doctor (as well as any health care provider) must inform you if they cannot, for whatever reason, follow your wishes as stated in your Living Will.  Thus, it is important to provide your doctor with a copy of your Living Will to ensure that your doctor will follow your wishes when it is time to do so.

This is one reason why you should give a copy of your living will to your doctor (or any health care provider) when you enter a hospital or other medical facility. If you are incompetent when you are admitted for medical care and have named someone in your living will to make decisions for you, that person must be informed if the wishes contained in your Living Will cannot be honored.

Your doctor (as well as any health care provider) who cannot honor your wishes must then help transfer you to another doctor (or health care provider) who is willing to carry out your directions.