Also known as acid, trips, microdots.

LSD is a chemical – lysergic acid diethylamide – sold in the form of tablets or tiny pieces of blotting paper impregnated with the drug. These `blotters' are often printed with a pattern to distinguish them from other brands of LSD. It is a Class A drug.

LSD begins to take effect 30 to 60 minutes after it is taken, and the trip begins to intensify, lasting for six to eight hours. The effect will then begin to fade, although the length of the trip depends on the strength of the LSD; a trip can quite easily last longer if a large quantity is used.

LSD has an extremely dramatic effect on all the senses in most people. Once again the effects are dose related. Users report visual effects such as intensified colours, distorted shapes and sizes, and movement in stationary objects. Perceptions will change and these will depend on the mood of the user, the setting in which the drug is taken and the company in which the user takes the drug. Sometimes the trip will be extremely euphoric, but on other occasions it might be terrifying.

Individuals who haven't used the drug before would be well advised to start with a half or even a quarter of a tab in order to become accustomed to the extraordinary effects of the drug, which can be intensely frightening for the uninitiated.

Individuals are able to influence the progress of the trip, as are companions of the drug user, so if an individual appears to be having a bad trip it is very important that companions look after the user, and guide them to a safe place, mentally and physically. Friendly reassurance and physical contact are very helpful in this state.

LSD can cause `flashbacks', short–lived, vivid re–experiences of part of a previous trip long after the drug's effect has ceased. Other psychological reactions can include the worsening of mental illness in people with underlying mental conditions.

LSD is not thought to affect the immune system, although many people report feelings of exhaustion after a trip. The drug is not thought to affect unborn children.