The main purpose of a medical power of attorney form also known as a health care power of attorney form, is made to give some one the right to control the decisions relating to your medical care if you can not communicate those decisions yourself.
You can also use a medical power of attorney form to establish additional, non-exclusive means for an individual to exercise his or her right to withhold, withdraw, and give consent to medical treatment. This can include mental health treatment, when you can no longer have the capacity to understand or communicate health care decisions.
Another reason to use a medical power of attorney form to protect your wishes to be left on life support. If no medical power of attorney form is declared your present condition is the only factor is whether the health care agent is given authority to take you off life support, as stated in law with the exact definition under G.S. 90-321 article 90 chapter 321.
Your medical power of attorney form will be effective once your physicians decides in writing that you lack the mental capacity to make health care decisions.