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

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.