Mich. Comp. Laws § 600.2157
Except as otherwise provided by law, a person duly authorized to practice medicine or surgery shall not disclose any information that the person has acquired in attending a patient in a professional character, if the information was necessary to enable the person to prescribe for the patient as a physician, or to do any act for the patient as a surgeon. If the patient brings an action against any defendant to recover for any personal injuries, or for any malpractice, and the patient produces a physician as a witness in the patient's own behalf who has treated the patient for the injury or for any disease or condition for which the malpractice is alleged, the patient shall be considered to have waived the privilege provided in this section as to another physician who has treated the patient for the injuries, disease, or condition. If a patient has died, the heirs at law of the patient, whether proponents or contestants of the patient's will, shall be considered to be personal representatives of the deceased patient for the purpose of waiving the privilege under this section in a contest upon the question of admitting the patient's will to probate. If a patient has died, the beneficiary of a life insurance policy insuring the life of the patient, or the patient's heirs at law, may waive the privilege under this section for the purpose of providing the necessary documentation to a life insurer in examining a claim for benefits.
MCL 600.2157