Preauthorization (also known as precertification, authorization, certification, prior authorization, guarantee of payment (GOP), or letter of authorization (LOA)) is when your medical treatment and costs are checked and then approved by Aetna International before they take place. This makes sure that you are covered and not subject to any unexpected bills. The services that need preauthorization include: A treatment or service that costs more than USD 500 (or the equivalent) A medical evacuation Inpatient admission and daycare treatment Psychiatric treatment Drug prescription lasting longer than three months Providers in the Aetna International network will usually seek preauthorization on the patient’s behalf. If the provider is not going to do this or if it is not part of the approved Aetna International network, customers will have to arrange preauthorization by contacting Aetna International themselves.