Lysergic acid diethylamide (LSD), also known as acid, is a psychedelic drug known for its psychological effects, which may include altered awareness of one’s surroundings, perceptions, and feelings as well as sensations and images that seem real though they are not. It is used mainly as a recreational drug and for spiritual reasons. LSD is typically either swallowed or held under the tongue. It is often sold on blotter paper, a sugar cube, or gelatin. It can also be injected.