By Lauren Smith

Last updated: 07 June 2024 & medically reviewed by Dr. Kimberly Langdon

LSD, commonly known as acid, is the most potent hallucinogen yet discovered: a drug that induces lengthy psychedelic trips with visual disturbances, sensory distortion, hallucinations, and spiritual experiences. Although not addictive, LSD can be abused. Despite this, the drug has also been explored as a treatment for substance use disorders, especially alcoholism.

Key takeaways:

  • LSD was first synthesized by the Swiss chemist Albert Hofmann in 1938. Working for the Basel-based pharmaceutical company Sandoz, he was researching ergot, a poisonous fungus that grows on rye and some other grains.

  • The United States made possession of LSD illegal in October 1968. The federal Controlled Substances Act of 1971 made LSD a Schedule I drug and therefore illegal to manufacture, distribute, buy, or possess.

  • An LSD trip begins 20 to 90 minutes after you ingest it and lasts between six and 12 hours or even longer. During this time your senses will be amplified or distorted, your emotions heightened, your thinking altered, and your perception of time-warped. 

LSD (Lysergic acid diethylamide)

What is LSD?

LSD is lysergic acid diethylamide. The abbreviation is derived from the German name for the molecule: Lysergsäurediethylamid.

It's a semi-synthetic psychedelic hallucinogen derived from a substance in the fungus ergot. Usually consumed on blotter paper, LSD warps the senses, amplifies emotions, elicits euphoria, and in large doses, brings about hallucinations, ego death, and mystical revelations. An LSD experience, known as a trip, lasts for six to 15 hours.[1]

Associated with the 1960s counterculture and the experiments of Harvard psychologist Timothy Leary, LSD was criminalized later that decade. However, its underground use for recreation and spiritual awakening continued. Recently LSD, along with other psychedelics, is being re-evaluated as a treatment for mental health conditions including depression, anxiety, and addiction.

What other names for LSD are there?

The most common street name for LSD is acid. It may also be called

  • blotter acid

  • dots or microdots: LSD in pill form

  • mellow yellow

  • stars

  • tabs

  • trips, tripper

  • window, window pane: LSD in gelatin tabs

  • Lucy

  • paper mushrooms [2][3]

When was LSD discovered?

LSD was first synthesized by the Swiss chemist Albert Hofmann in 1938. Working for the Basel-based pharmaceutical company Sandoz, he was researching ergot, a poisonous fungus that grows on rye and some other grains (and, decades after Hofmann’s experiments was theorized as a cause of the hysteria about witches in 17th-century Salem). 

Hofmann was looking for a respiratory and circulatory stimulant when he reacted lysergic acid (a derivative of ergotamine, an alkaloid from ergot) with ammonia-derivative diethylamine. But the compound he produced, then known as LSD-25, was dismissed by Sandoz when it appeared to only make lab animals overly excited.

Hofmann himself didn’t recognize the psychedelic properties of the compound until he re-synthesized it in 1943 and accidentally ingested a tiny amount. Within minutes he was experiencing “an uninterrupted stream of fantastic pictures, extraordinary shapes with an intense, kaleidoscopic play of colors.”[4]

After further experiments, many of them on himself, Hofmann decided LSD could be a powerful psychiatric treatment. After the war, that’s how Sandoz began marketing it, as Delysid, a cure for schizophrenia, criminality, ‘sexual perversions, and alcoholism. It also encouraged psychiatrists to take the drug themselves in order to understand the experience of patients with schizophrenia. Eventually, around 40,000 patients were treated with LSD.[5]

Some of those patients were unknowingly and illegally dosed by the CIA. The intelligence agency had purchased the world’s entire supply of the drug in the 1950s, seeking a truth serum and pharmaceutical means of mind control and torture. The clandestine research program, code-named MKUltra, ultimately concluded that LSD’s psychoactive effects were too unpredictable.

The United States made possession of LSD illegal in October 1968. The federal Controlled Substances Act of 1971 made LSD a Schedule I drug and therefore illegal to manufacture, distribute, buy, or possess. While researchers and drug developers are permitted to study it, they must receive the approval of the Drug Enforcement Administration (DEA) and Food and Drug Administration (FDA).

Also in 1971, the United Nations Convention on Psychotropic Substances made LSD a Schedule I drug around the world. That effectively made the prohibition of LSD and other recreational drugs a condition of UN membership.

Under the U.S.’s Controlled Substances Act, Schedule I drugs are thought to have a high potential for abuse, no accepted medical use, and a lack of safety for use under medical supervision. However, later research has cast doubt on the harm of LSD and other psychedelics and suggested they may, as Albert Hofmann believed, have powerful therapeutic use. There has therefore been a push to reclassify the psychedelics LSD, psilocybin (magic mushrooms), and DMT to facilitate further research.[6]

Some U.S jurisdictions have already relaxed laws against LSD. Following a referendum in 2020, Oregon decriminalized the personal possession of small amounts of illicit drugs including LSD (40 or fewer units) on 1 February 2021.[7] Legislators in California have also contemplated a bill that would decriminalize the possession of hallucinogenic drugs including LSD.[8]

The effects of LSD

LSD has a range of effects, from euphoria to panic, elevated heart rate to ego death. Responses vary widely between individuals and doses, so you can’t predict how LSD will affect you.

Short-term effects of LSD

LSD’s mode of action isn’t fully understood. It appears to partly produce its effects by binding to serotonin receptors in the brain, especially the 5-HT2 receptor.

Effects are seen in the prefrontal cortex, including perception, mood, and cognition, and in areas of the brain that govern arousal and physiological responses to stress.[9]

LSD is very potent: doses as low as 20 micrograms (mg) produce noticeable effects.[1]

Short-term effects include:

  • visual disturbances: including intense color, halos, and trails around objects, swirling patterns, and spinning fractals. Objects may appear to move, ripple, morph, or dissolve. They may seem larger than usual. Visual disturbances are seen with eyes open and closed.

  • sensory distortions: things may sound, smell, or taste different than usual. You may experience synesthesia. Time may slow.

  • hallucinations: seeing, hearing, feeling, smelling, and tasting things that aren’t there.

  • mood changes: During good trips: excitement, euphoria, awe, and reduced anxiety. Enhanced capacity for introspection. During bad trips: anxiety, panic, paranoia, confusion, dread, hopelessness, even suicidal ideation, and psychosis. All emotions, positive and negative, may be heightened.

  • physical effects: dilated pupils, wakefulness, elevated heart rate, elevated blood pressure, elevated body temperature sweating, reduced appetite, nausea, dry mouth.

At very high doses, you may experience ego death (the dissolution of the sense of self) and a change in body image.[10]

These effects last, at most, 20 hours. However, you may also experience an afterglow: an improved mood and feeling of social connectedness that lingers for a couple of days after.[11]

Long-term effects of LSD

For most people, the positive and negative effects of an LSD trip will ebb in just a few days. But occasionally there will be lingering effects.

  • flashbacks: Some people may experience flashbacks of their LSD experience for weeks, months, and even years. Usually, these are visual disturbances: halos around objects, trails after images, illusions of movement, and visual snow. In a small number of people, these flashbacks are persistent and a source of distress and are diagnosed as hallucinogen persisting perception disorder (HPPD).[12]

  • worsening of some mental health conditions: While reports about LSD causing people to be permanently psychotic are exaggerated, psychedelics can worsen symptoms or cause a relapse in people who have already experienced mental health conditions involving psychosis. They can also accelerate the onset of schizophrenia in young people predisposed to it and should be approached with caution by people with a family history of psychotic illness.[13] Additionally, bad trips can worsen anxiety and panic disorders.

  • Improved mental health: Conversely, LSD is being studied as a potential treatment for depression, anxiety, and alcohol abuse. Experimental studies have found symptom improvement lasting up to a year after one or two doses.[14]

What does LSD feel like?

An LSD trip begins 20 to 90 minutes after you ingest it and lasts between six and 12 hours or even longer. During this time your senses will be amplified or distorted, your emotions heightened, your thinking altered, and your perception of time-warped. 

Users often report that colors are more intense or unnaturally bright, surfaces seem to ripple or “breath,” or kaleidoscopes of color and geometric patterns overlay their vision and appear behind their closed eyelids. These patterns may shift based on your thoughts, emotions, and music. Music may seem more intense and sound echo-y. 

You may experience synesthesia, or a cross-wiring of your senses, seeing music, tasting color, etc. Sometimes you’ll experience hallucinations.

The experience can be unpredictable, influenced by the dose, and your personality, mood, imagination, expectations, and surroundings. 

Some LSD experiences are overwhelmingly positive: you may be suffused with joy and wonder, arrive at new insights into yourself, feel at one with others and the universe, and have intense spiritual experiences. With high doses, you may experience ego death, your sense of self temporarily dissolving.

However, some people find the distortions and hallucinations of LSD to be anxiety-inducing or terrifying. During one of these ‘bad trips,’ you may feel you are in a nightmare, going insane, or even dying.

Related: How long does LSD stay in your system?

Types of LSD

When just synthesized, LSD is a crystalline powder. But it’s not usually consumed that way. 

There are several different forms of LSD sold on the street.

Blotter paper

LSD is most commonly ingested on blotter paper, saturated with a liquid dilution of the drug. That paper is divided into 1/4 inch squares known as “tabs,” pre-printed with miniatures designs, such as hearts, butterflies, smiley faces, and strawberries.

The paper is perforated so it can easily be divided into tabs. Each tab has a single dose, usually between 100 and 200 μg. However, the dosage can vary between batches and it’s impossible to tell the strength of a tab before taking it.[15]

Tabs are placed under or on the tongue or anywhere in the mouth and left to absorb for three to 15 minutes. This allows LSD to enter the bloodstream.

Liquid LSD

LSD is water-soluble and can be dissolved in water or alcohol. It’s sold in liquid form in small dropper bottles. Usually, you’re supposed to take one drop, which delivers a dose that should be specified on the bottle but may range from 75 to 300 μg. You can put a drop under your tongue, so it’s absorbed into your bloodstream, or put the drop into food or drink and ingest it that way. Ingested liquid LSD will take longer to reach your bloodstream, especially if you have food in your stomach.[16]


In the 1960s, LSD was most commonly consumed in tablets and the form is still encountered today. The smallest pills are known as “microdots."

Gelatin tabs

Another 1960s form was 'windowpanes': liquid LSD mixed with gelatin and food coloring, poured into a mold, and dried. Gelatin tabs can hold more LSD than paper can absorb: reportedly up to 600-700 mg.

Sugar cubes

Liquid LSD can also be dropped onto sugar cubes. This was the way LSD was first illicitly distributed before demand necessitated mass manufacture.

Read here to learn more about what LSD looks, smells, and tastes like.

Is LSD addictive?

As part of the backlash against the counterculture and in the first decades of criminalization, LSD was portrayed by law enforcement, doctors, and the media as dangerously addictive. However, a softening of attitudes has led to a reassessment of LSD and other hallucinogens and revealed that they don’t lead to compulsive behavior or addiction.

We now understand dopamine to be the root of addiction, and hallucinogens don’t elicit its release. In experiments, animals can’t be trained to self-administer hallucinogens as they can with addictive drugs of abuse.[17]

However, LSD can be abused: used excessively and in a way that disrupts an individual’s life. It can also be taken alongside more addictive drugs as part of polysubstance misuse.

LSD tolerance

Another factor limiting the addictive potential of LSD is how quickly users develop tolerance to it. Tolerance to LSD manifests 24 hours after its first use and peaks around the fourth day. During this time, the mental effects of LSD will be muted, even when the dose is quadrupled. This means everyday usage of LSD is very unlikely. However, tolerance usually ebbs after five days of abstinence so some people may use LSD once per week.[18]

LSD as a treatment for addiction

LSD has been studied as a potential cure for addiction, specifically alcoholism, since the 1950s. In a series of studies conducted in Canada that decade, around half of all alcoholics given one dose of LSD were abstinent one year later.[19] Alcoholics Anonymous founder Bill Wilson himself experimented with LSD and believed the drug could cause a “spiritual awakening” that propelled alcoholics toward recovery.[20]

The success rate of these Canadian studies has never been duplicated, but interest in LSD therapy for addiction has recently been revived. A review of six trials performed on 500 patients in alcoholic treatment programs in the 1960s found that 59% of alcoholics who received one dose of LSD reduced their alcohol misuse compared to 38% of the other group. The effects lasted six months after one dose but had disappeared by a year.[21]

Can LSD kill you?

You very likely can’t overdose on LSD. While taking too much might make for a frightening trip, there’s little chance it will physically harm you.

A survey of scientific literature and media reports found just two deaths credibly attributed to “LSD toxicity.” In two cases, the doses consumed were massive—so large they were likely obtained directly from an LSD manufacturer and not street dealers of tabs. One dose was estimated at the equivalent of 320mg intravenously—3,200 times a typical recreational dose. The lethal dose of LSD has been estimated at 100mg.

But even when people take similarly massive doses, they’ve survived with appropriate medical care.[22] 

LSD has also caused death by causing irrational, psychotic, or suicidal behavior. However, these cases are very rare and the role LSD played in them is often unclear.[23]

Most of the time when people refer to LSD overdoses they mean they’ve had a bad trip, experiencing anxiety, panic, and frightening hallucinations. While bad trips are more likely at higher standard doses, you can also experience a bad trip at lower doses. Dosage matters less than your mindset and surroundings.

How much LSD is safe to take?

As little as 20μg (0.02 milligrams) of LSD produces noticeable effects in humans. Normal recreational doses are similarly microscopic: 100-400μg or 0.1 to 0.4 mg.

However, people report taking much higher doses, which led to harrowing trips but didn’t cause them lasting harm.[24]

Can LSD be good for you?

With addiction and overdose unlikely and even physiologically impossible, there’s been a reevaluation of LSD as a medicine and therapy aid, as Hofmann first envisioned.


Some people claim that taking sub-threshold doses of LSD (or psilocybin) one or more days per week enhances their creativity and boosts their energy and mood. At these tiny doses—as little as one-fifteenth of a tab—they don’t experience any sensory distortion or hallucinations. Instead, they claim their focus is actually honed.

There are many anecdotal reports of the benefits of microdosing. However, the first placebo-controlled study of the practice suggests the boost may just be a placebo effect.[25]

LSD therapy

Alongside other psychedelics, LSD is also being considered as an adjunct to psychotherapy. Psychedelics are thought to dissolve the ego and promote neuroplasticity, allowing new, healthier thought patterns to be established—in as little as one dose. They can therefore make the individual more receptive to psychotherapy.

The length of LSD’s trips makes it less suitable for therapeutic use than psilocybin (three to six-hour trips) and DMT (as brief as 15 minutes). However, it’s being studied as a  treatment for anxiety, depression, and addiction, especially alcoholism. One study found that LSD reduced anxiety in patients facing a life-threatening illness and gave them a sense of self-assurance, relaxation, and mental strength which lasted for around 12 months.[26]

Read here to learn more about LSD therapy.

Cluster headaches

Preliminary research indicates that LSD may prevent cluster headaches. Six patients treated with a non-hallucinogenic analog of LSD reported significant reductions in these debilitating headaches, with some free of cluster headaches for weeks or months.[27]

Staying safe with LSD

LSD remains illegal in most of the world. But if you decide to use the drug, you can take steps to minimize the risk to your health.

  • Only trip in a safe place. Your surroundings can influence your experience on LSD. Only take LSD in a comfortable location where you can manage your sensory input and stay away from hazards such as heights, traffic, and bodies of water.

  • Don’t trip in a bad frame of mind. This increases the likelihood of a bad trip.

  • Have a sober ‘sitter.' This person can intervene if you start acting irrationally.

  • Don’t mix LSD and other substances, including prescription medication. Especially drugs and medications, like antidepressants and other psychedelics, that act on serotonin. The combination can overload your nervous system with the neurotransmitter and in severe cases, cause death.

  • Don’t drink alcohol. The combination of alcohol and LSD comes with a risk of bad trips, falls and accidents, and nausea and vomiting. On LSD you might be unable to tell how drunk you are and inadvertently consume more alcohol than you intend.

  • Seek medical attention. If you’re experiencing a terrifying trip, believe you might be a danger to yourself and others or are having any other adverse reaction, you should seek appropriate medical help.