Md. Code, State Personnel and Pensions § 9-504

(a) An employee who uses sick leave for 5 or more consecutive workdays for personal illness or disability or the illness or disability of a member of the employee's immediate family may not receive payment under this subtitle unless the employee gives the employee's immediate supervisor an original certificate of illness or disability.

(b) The certificate required under subsection (a) of this section shall be signed by one of the following:

(1) a medical doctor who is authorized to practice medicine or surgery by the state in which the doctor practices;

(2) if authorized to practice in a state and performing within the scope of that authority:

(i) a chiropractor;

(ii) a clinical psychologist;

(iii) a dentist;

(iv) a licensed certified social worker – clinical;

(v) a nurse midwife;

(vi) a nurse practitioner;

(vii) an oral surgeon;

(viii) an optometrist;

(ix) a physical therapist;

(x) a podiatrist; or

(xi) a licensed professional counselor – clinical;

(3) an accredited Christian Science practitioner; or

(4) a health care provider as defined by the federal Family Medical Leave Act.

(c) The certificate required under subsection (a) of this section due to an employee's illness or disability shall include a prognosis about the employee's ability to return to work.