S.C. Code Ann. § 44-26-50

If the client is found incompetent to consent to or refuse major medical treatment, the decisions concerning his health care must be made pursuant to Section 44-66-30 of the Adult Health Care Consent Act. An authorized designee of the Office of Intellectual and Developmental Disabilities may make a health care decision pursuant to Section 44-66-30(A)(9) of the Adult Health Care Consent Act. The person making the decision must be informed of the need for major medical treatment, alternative treatments, and the nature and implications of the proposed health care and shall consult the attending physician before making decisions. When feasible, the person making the decision shall observe or consult with the client found to be incompetent.