1. Performance of services and procedures required by the patient, indispensable, and consistent with the diagnosis in accordance with standards of good medical practice, performed at the proper level, and provided in the most appropriate setting. Medical necessity must be established (via diagnostic and/or other information presented on the individual claim under consideration) before the carrier may make payment. 2. Cal. Wel. & Inst. Code 14059.5 defines medical necessity when it is reasonable and necessary to protect life, to prevent significant illness or significant disability, or to alleviate severe pain. Also see medically necessary care .