A deferral is a determination and notification that a blood donor is unsuitable to donate blood. Deferrals may occur as a result of test results, high-risk donor activity, physical or historical donor characteristics that would make donation potentially harmful to the donor, or any other factor that disqualifies the donor under either FDA regulations or guidances or AABB Standards. Deferrals may be temporary (with a defined end date), indefinite, or permanent. See “reentry” for a description of the process of regaining eligibility after a deferral.