LSD (acid) is short for d-lysergic acid diethylamide. LSD itself is not found naturally, but is considered semi-synthetic, as it was first prepared by Albert Hofmann by altering a molecule found in the ergot fungus. Hofmann discovered its unexpected properties when testing it on himself in 1943.

LSD usually comes in little paper squares (blotter) which have been soaked in tiny quantities of LSD solution and dried. Instead of paper, LSD has also been found in coloured gelatine pieces (gel tabs), tablets or very tiny pills called microdots. Once common was the use of sugar cubes which had a drop of LSD solution put on them. Alternatively, a solution can be directly dropped onto the tongue from a dropper bottle. When dealing with an actual LSD solution, there is a risk of taking much more than intended.

However it comes, the drug is held under the tongue and/or chewed. Few people would want to take LSD very regularly, people usually take it seriously and treat a trip as an infrequent and special experience.

Sometimes, doses of ‘LSD’ have turned out to be other chemicals such as the NBOMe drugs. This is a serious problem, because taking too much of these is much more dangerous than taking too much LSD, and could even kill.

LSD is a psychedelic lysergamide hallucinogen. How LSD produces its psychoactive effects is very poorly understood, partly because the action of LSD is so diverse. However, the psychoactive effects of LSD in humans shares many key features observed with psilocybin (magic mushrooms) and mescaline (e.g. peyote cactus). Studies have hinted that psilocybin might suppress the connectivity between brain areas, perhaps changing the way sensory information is filtered by the brain.

As it stands much more research is needed to fully understand how LSD and other hallucinogenic drugs produce their psychoactive effects.

LSD (as well as other hallucinogens like psilocybin) does not necessarily produce a selection of fairly predictable, repeatable sensations and effects like some drugs that belong to other classes such as stimulants. LSD produces a psychedelic experience, often called a ‘trip’, and no two LSD ‘trips’ are the same.

Some people have reported the psychedelic experience to be one of the most intense experiences of their lives. LSD experiences might well be experienced as positive, frequently ‘mystical’, and personally meaningful (and usually draining). However, overwhelming experiences of this nature can be miserable or terrifying too, with horrible effects which may last anywhere from a few moments or several hours.

LSD does not kick in straight away but effects usually come on within an hour. The peak of the trip might last for over 4 hours, with decreasing effects continuing for up to 12 hours afterwards.

With LSD, some people have become anxious, panicky and confused (especially if a very large dose has been taken). Occasionally, a trip can be traumatising.

Passing unpleasant moments are common during a strong trip. Long-forgotten or traumatic events might come to the surface. Longer lasting horrible effects are usually the result of an inappropriately high dose, an inappropriate setting (see ‘set’ and ‘setting’ below), anxieties and other negative emotions present in the user’s mind-set, or pre-existing mental health issues. Even so, it is also possible for unpleasant experiences to happen for no apparent reason, even if the user is well-prepared.

A big enough dose of LSD will produce a powerful psychedelic experience where how you think, see and feel is radically altered. Even with small doses people may experience hallucinations such as patterns on wallpaper moving, and changes in the way they think. Like all drugs a larger dose of LSD will produce a more intense effect. However, due to the high potency of LSD and the varying amounts present in a particular product, it is very difficult to measure how big an effect the drug will have.

More so than other drugs, an individual’s expectations and choices strongly affect the experience.

The experience is often emotionally, physically and mentally draining, and it is common to feel worn out for a day or so after use.  Some feel detached or even alienated from reality. Some report feeling fuzzy-headed. Alternatively, a trip can give people an emotional lift that lasts days.

A great deal of misunderstanding surrounds the phenomenon of ‘flashbacks’ after using LSD. Although these are poorly researched, there is no evidential basis for the myths that years after using LSD, people suddenly start tripping violently for no reason, causing all sorts of chaos like car crashes. However, in the days after a psychedelic experience, particularly after high doses, it may be surprisingly common, based on survey data, to get echoes of the trip experiences coming back, which may feel like momentarily tripping again. Such ‘flashbacks’ are usually not unpleasant or problematic. They are often brought on by alcohol or cannabis.

Much more rarely, long-lasting changes in perception called HPPD can happen (see below), this could be a seriously disabling condition at worst, unlike the brief flashbacks people get as an after-effect of tripping on LSD.

The first two decades following the discovery of LSD yielded intense research activities. These included LSD’s experimental use in psychotherapy, in the attempt to help with the treatment of a range of psychological problems and psychiatric illnesses. Although to modern eyes, some of this activity fell short of ethical and methodological standards, these years yielded some promising results.

Following the legislative control of LSD, clinical research ground to a halt, and regulatory and financial obstacles currently stand in the way of research on the therapeutic potential of LSD. Despite this, small steps have been taken in exploring the use of LSD in psychotherapy and in the treatment of cluster headaches, and there has been renewed interest in the use of LSD in the treatment of alcoholism.

It may be tempting for people to try to self-treat with LSD. Evidence that LSD can be an effective treatment with manageable risks only applies to the controlled procedures used in clinical studies, where professional psychotherapists help guide the patient’s experience. LSD alone (or any other psychedelic substance for that matter) is not the treatment because the idea is that LSD should be combined with professional psychotherapy. Without the appropriate safeguards, LSD may in fact worsen conditions like anxiety and other mental health issues.

LSD is less likely to cause physical harm to your life and health than many drugs with less fearsome reputations such as alcohol. However, the experience is often challenging and can be traumatic.

Risks of physical harm or death

Because it is so potent, the tiny dose used to trip on LSD is far below the quantity that would be toxic, so people do not fatally overdose on LSD. However, some other drugs with both hallucinogenic and stimulant (amphetamine-type) effects are sometimes sold as LSD or confused with LSD, and overdoses of these can cause unpleasant effects (e.g. trips lasting for much more than a day), or can cause harm or death. One such drug, DOB, can take 3 hours to kick in, potentially leading to overdoses if the user mistakes the effects for weak LSD and takes too much. It is important to be very cautious and suspicious of illegal drugs as the quality and authenticity of drugs is entirely unregulated. More recently, a newer group of highly potent phenethylamines (e.g. NBOMe analogues) have been detected on blotters and these might also be sold as LSD. In this case, details about their activity and toxicity are currently unclear.

Another risk of harm and death from LSD is the risk of accidents and injuries caused by odd behaviour and a lack of judgement. Common stories of people on LSD doing stupid things like blinding themselves by looking at the sun, or jumping out of high windows believing they can fly, are mostly mythological, but psychedelics do make people do strange things. People tripping on psychedelics are at risk of walking into roads for example, and a handful of suicides, suicide attempts, and self-injuries have been associated with the effects of LSD (though mostly in people with previous history of mental health problems).

Injuries and even deaths have resulted from encounters with police whilst tripping. On LSD you may lack the insight to understand and comply with police and therefore make yourself a victim of police violence and forcible restraint.

Risk of psychological or mental harm 

Rarely, people do have a prolonged and devastating bad trip, sometimes called a ‘psychedelic crisis’, and this can be very traumatic and even psychologically harmful. It may be impossible to entirely eliminate the risk of this happening, but certain factors make it more likely. If someone is going through a difficult time emotionally when they take psychedelics, if they are in an unfamiliar and chaotic setting with people that they do not know or trust, or if they take a very high dose, they are at far greater risk of having a bad experience.

As with any severe health problem caused by drugs, it is important to get medical help if you are with someone who seems to be undergoing a psychedelic crisis which you cannot relieve by supportive involvement. A trip cannot be turned off once it has started, and so sedation with benzodiazepines is usually used to lessen the traumatic effects and prevent the individual from hurting themselves or others.

People usually recover well from a psychedelic crisis when the drug wears off, or shortly thereafter. However, in very rare cases, psychotic episodes might persist even after the drug effects should have passed. The risk of this happening is negligible to people without a history of psychiatric problems, but people with pre-existing mental health problems or a predisposition to mental health problems (such as close relatives with anxiety, depression or schizophrenia) are thought to be at risk of lasting symptoms or relapses of existing conditions if they take psychedelics. The lack of sufficient evidence makes it difficult to quantify this risk.


HPPD or ‘Hallucinogen Persisting Perception Disorder’ is a very unusual and potentially harmful effect of LSD and other hallucinogens. HPPD is most often experienced as re-appearance of some of the effects experienced during the previously occurring hallucinogenic drug experience after some time without the drug. In most cases HPPD follows a traumatic hallucinogenic drug experience (‘bad trip’). In some cases, sufferers may feel detached from normality or the world.

HPPD was reported occasionally as longer-lasting, though complete or partial recovery usually occurs after weeks or months. Lingering HPPD has been reported more often following the use of LSD rather than other hallucinogens, higher doses and drug combinations. This kind of HPPD may occur in people with underlying psychiatric conditions or genetic vulnerabilities, but the evidence is very incomplete.

Mental health issues, such as anxiety and depression, even if never formally diagnosed, increase your chance of a bad experience or psychological harm. The chance of triggering psychotic episodes  is very low for most people, (especially when the user takes steps to contemplate and minimise the risks, see ‘set’ and ‘setting’ below) but higher for people who have, or have ever had a psychotic conditions such as schizophrenia, or their close relatives.

LSD should not be taken by those who are on psychiatric medications in order to exclude any potential for adverse drug interactions.

LSD is not considered an addictive drug. One factor that makes some drugs, like cocaine, addictive is that users (whether humans or rats) can find it difficult to stop using again and again to recapture the pleasurable features. Whilst LSD can produce intense joy, this cycle of compulsive re-use cannot occur because a dose that produced intense effects will do little or nothing if repeated in the following days. It takes a little while before the brain loses this resistance to psychedelic effects.

Furthermore, whilst lab animals eagerly take cocaine, few animals appear to self-administer LSD. However, some people are very attached to LSD, perhaps finding it an important spiritual tool, and take it frequently.

LSD has low risks to physical health, because it is not addictive and rarely used regularly. However, LSD has the potential to be an overwhelming and profound experience, and not always in a way the user might want. If people understand, as far as is possible, what LSD does, many will come to the conclusion that it is not for them.

Being cautious

Not all of the ‘LSD’ available is actually real LSD, and even the dealer may not know this. LSD has a nearly unique property; exceptionally low toxicity. That means that taking far too much might be incredibly distressing (you might even need medical help), but it will probably not harm your body. However, if the ‘LSD’ is actually another drug like an ‘NBOMe’ chemical, taking much too much could kill you. The trade in LSD is illegal, which makes it especially hard to be entirely sure that the drug is just what it is supposed to be. This risk is particularly high if you intend to take an unusually large dose from a supply you have not used before.

Being prepared

It is difficult to measure doses of LSD reliably as they are very inconsistent, and impossible to fully imagine the effects if you have not tried it before. Therefore, LSD should be avoided if the user is not prepared to have a more overwhelming experience than they might ideally have intended. Many people choose not to take psychedelics because they do not want to feel out of control.

The effects that psychedelics have are normally only controllable to some extent but proper planning is advisable. Whilst many people think that the use of powerful and controlled drugs can never be considered entirely responsible and well-judged, people who are informed about the factors which affect the mood of a trip are certainly less likely to experience unpleasant thoughts and effects.

Set and setting

A useful way of remembering the factors that help determine whether a trip is rewarding or nightmarish is the concept of ‘set’ and ‘setting’.  A person’s ‘set’ (or mind-set) includes their mood, disposition, thoughts and expectations. A person’s ‘setting’, is the specific place and social situation in which they take the drug. If an anxious and miserable person accepts LSD without having planned for this at a chaotic party where they know and trust no-one, then their trip may be a disaster. Taking hallucinogens in a calm, familiar place, with someone you trust to be your sober ‘trip-sitter’ is far less likely to be something regretted for life.

Having a sitter

Psychedelic drugs trigger a complex range of altered states of consciousness which can make people highly suggestible, especially in the presence of other people. This also means that their ideas strongly influence the way that they perceive the world. For example, once the thought has occurred that they might be dying, they may see their skin appearing to go grey and blotchy. However, this suggestibility is not necessarily all bad; it means that a sober helper, (sometimes called a ‘trip sitter’) can often successfully reassure them, or distract them with a change of scene or showing them something. It is essential to remind someone who is showing signs of beginning to have problems that what they are feeling is not real, and that they have taken a drug which will wear off. Reassuring comments and gestures can be helpful.  Have a discussion before you begin as to what to do if things do not go smoothly.

LSD is probably one of the most mythologized and demonised drugs, and its history is full of episodes which are as outlandish as the stories, such as the illegal experiments with the drug carried out by American and British intelligence agencies. Countless urban myths exist about bizarre and frightening things people did whilst tripping.

“Bad Acid”

People have believed in batches of so-called “bad acid” which are blamed for horrible effects and bad trips. Doses of different batches can be very variable and ‘bad’ experiences with LSD can usually be related to unwanted high doses, irresponsibility or unpreparedness and/or the ingestion of a different substance. There are no different types of LSD.

LSD stays in your spinal fluid, causing flashbacks years later

LSD does not stay in your body for long. Flashbacks and HPPD are poorly understood, but the symptoms occur in the absence of LSD.

Orange Juice/ Vitamin C can be used as an antidote to stop a bad trip

This is not true, there are no easy home remedies to end a trip, although doctors use benzodiazepines to ease agitation. However, people are very suggestible when tripping and this can contribute to the perception of such effects.

You can be declared legally insane if you take LSD more than seven times

There is an old rumour that taking LSD more than seven times means that you can be declared legally insane. This is not true and there are plenty of people who have taken LSD more than seven times and are not insane.

People going blind staring at the sun

The rumour about people going blind from taking LSD and staring at the sun was created by a TV show in the 1960s. However, there have been a few case reports of people partially damaging their eyes from staring at the sun whilst on LSD. People do strange things whilst on LSD and LSD dilates your pupils which exposes your eyes to more light than usual.

People think they can fly and jump out of a window

People have fallen out of windows and off cliffs whilst on LSD, but these were probably accidents due to impaired judgement, or suicides, rather than thinking they could fly.

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