Topic Overview

LSD (lysergic acid diethylamide) is the most widely used hallucinogenic drug. Hallucinogenic drugs cause a person to see vivid images, hear sounds, and feel sensations that seem real but are not. LSD is also called acid, doses, hits, Microdot, sugar cubes, tabs, and trips. It is odourless and colourless and has a slightly bitter taste. It can be obtained as a coloured tablet, clear liquid, or thin square of gelatin (window panes) or on blotter paper. Most often, LSD is licked off blotter paper or taken by mouth. But the gelatin and liquid forms can be put in the eyes.

The effects of LSD are unpredictable and depend on the amount taken; the person's personality, mood, and expectation; and the situation in which the drug is used. Effects are usually felt within 30 to 40 minutes after taking the drug. The LSD experience is often called a "trip" and can last up to 12 hours.

LSD causes:

  • Dilated pupils, increased body temperature, increased heart rate and blood pressure, sweating, loss of appetite, sleeplessness, and dry mouth.
  • Changes in sensations and feelings. The person may feel several different emotions at the same time or rapidly swing from one emotion to another. Also, the person may confuse sensations and feelings, such as "hearing" colours or "seeing" sounds.
  • Loss of time. The person may feel that time is standing still.
  • Delusions and visual hallucinations, if taken in large doses. Delusions are false beliefs, and hallucinations are seeing and hearing things that are not present.

A "bad trip" may contain terrifying thoughts, feelings, and fears. Also, LSD can cause flashbacks, in which the person suddenly relives certain aspects of the experience without having taken the drug. Flashbacks may occur a few days or more than a year after use of LSD.

Serious psychiatric conditions can develop after even one use of LSD. The cause of these effects is not known. The effects include:

  • Drug-induced psychosis. Psychosis is a serious condition in which the person has lost the ability to recognize reality, think rationally, or communicate with others. The person may have dramatic mood swings, ranging from being extremely overactive (mania) to severe depression. Psychosis from LSD may last for years.
  • Hallucinogen-persisting perception disorder (HPPD). With HPPD, the person has flashbacks in which the person experiences recurrences of some of the sensory distortions that occurred while under the influence of the drug. The person may have the same flashback for years after stopping use of LSD.

LSD can lead to substance use disorder. And it does require increasingly higher amounts to obtain the same effect (tolerance).

LSD is typically out of a person's system within 24 hours, and standard drug screens (toxicology tests) are not able to detect it. But special laboratory tests can be used to detect LSD in the blood.

Signs of use

It is difficult to detect LSD use. Things that point to LSD use may include:

  • Dilated pupils, sweating, loss of appetite, sleeplessness, and dry mouth if recently taken.
  • Possession of small squares of blotter paper (sometimes stamped with cartoon characters) or other forms of the drug.


Current as of: November 8, 2021

Author: Healthwise Staff
Medical Review: Patrice Burgess MD - Family Medicine
Brian D. O'Brien MD - Internal Medicine
Adam Husney MD - Family Medicine
Martin J. Gabica MD - Family Medicine
Kathleen Romito MD - Family Medicine
Peter Monti PhD - Alcohol and Addiction
Michael F. Bierer MD - Internal Medicine, Addiction Medicine