It means that you need a treatment to heal from your illness or injury or to save your life. Discusses incident to guidelines briefly. 2 Lists specific codes 97597 97598 97602 and states these codes cant be used for only a dressing change. . Letter of Medical Necessity LMN Benefit Administration Company PO Box 550 Seattle WA 981110550 2066251800 Under Internal Revenue Service IRS rules some health care services and products are only eligible for. To some degree definitions of medical necessity vary from insurer to insurer and state to state. Under Internal Revenue Service IRS rules some health care services and products are only eligible for reimbursement from a Medical Spending Account when your doctor or other licensed health care provider certifies that they are medically necessary. Medicare for example defines medically necessary as. A service is medically necessary if it is reasonably calculated to prevent diagnose co...