This is a statutory form that is provided in the Oklahoma Statutes and provides a means for you to express a variety of health care choices and decisions: specific instructions for life sustaining procedures or treatment, appointment of a health care agent, and the making of anatomical gifts. An individual of sound mind and eighteen (18) years of age or older may execute an advance directive governing the withholding or withdrawal of life sustaining treatment. The advance directive must be signed by the declarant and witnessed by two individuals who are eighteen years of age and who are not legatees, devisees, or heirs at law of the declarant.