LSD

What it feels like

A trip as it unfolds, what it does to seeing, hearing and feeling, and how the very first one went.

Over the hours

• The first hour, Coming up: Taken by mouth, it reaches its highest level in the blood at about an hour and a half.
• About 2½ hours, The peak: The effects are at their strongest.
• 8–12 hours, Coming back: About eight hours after 100 µg, and eleven or twelve after 200.

What you see, as the dose rises

• Low, Noticeable: 25 µg. Already measurable, and in one trial nearly half of people noticed changes in what they saw.
• Light, Alive: 50 µg. Colour richer, texture sharper and starting to move; bright lights glow.
• Full, Breathing: 100 µg, a full dose: surfaces undulate and pattern grows out of texture, and moving lights leave trails of separate, stationary images.
• Strong, Geometry: 150 µg. Pattern spreads over anything textured, and sound reshapes what you see.
• Very strong, Latticework: 200 µg. Flowing latticework can fill the view; the self dissolves further, and anxiety becomes more likely. On 250 µg, LSD's discoverer saw everything waver as if in a curved mirror.

What it can feel like

• Sound into sight: Sounds changing what you see is one of its main effects.
• Music: Music hits harder — more wonder, transcendence, power and tenderness — and songs that meant nothing to you can suddenly feel personal.
• Closeness: Well-being, happiness, openness, trust and feeling close to others all rose in volunteers.
• Unreal: The world or yourself can feel unreal — derealisation and depersonalisation — though volunteers mostly experienced it positively.
• Self: At 200 µg the sense of being a separate self dissolves more than at 100.

The first deliberate trip was a hard one. On 19 April 1943, Hofmann took 0.25 mg, which he thought the smallest amount that could do anything — more than the top dose, 200 µg, in a modern dose study. At its worst he feared he was going insane or dying, the furniture took threatening forms, and his neighbour seemed a witch in a coloured mask. As it eased, he began to enjoy the images, and the next morning, he wrote, the garden "glistened and sparkled in a fresh light".

What tips a trip one way or the other? Going in open, accepting and surrendered predicts good experiences; going in preoccupied, apprehensive or confused predicts hard ones.

What's happening in the brain

One receptor, held for hours, and a visual cortex that starts talking to everything. The model lights each one as you read.

One lock, held tight

LSD switches on the serotonin 5-HT2A receptor: block it with ketanserin and the trip is blocked. It binds that receptor more potently than psilocin, mescaline or DMT, and comes off it very slowly — a loop of the receptor closes over it like a lid, which researchers suggest could be part of why it lasts so long.

The visual cortex, talking to everything

Scanned with eyes closed, blood flow to the visual cortex rose, and the primary visual cortex began communicating with far more of the brain — the more it did, the more vivid the imagery people reported. Its alpha rhythm weakened, too.

The thalamus

The thalamus relays what your eyes see on to the visual cortex. On LSD its connections across the brain strengthen, and the sensory networks become more connected while the brain's higher, associative networks become less so — all of it blocked by ketanserin.

The self coming loose

The default mode network, which this hub anchors, held together less in step with ego dissolution; and the weaker the link between the parahippocampus and the retrosplenial cortex, the more people's sense of self and of meaning changed.

Fear, quietened

LSD lowered the amygdala's response to fearful faces, and the lower it went, the stronger the drug's effects felt.

As a medicine

Two recent trials for anxiety, and what microdosing studies found.

In a 2023 trial, 42 people with anxiety, some facing a life-threatening illness, had two LSD-assisted therapy sessions. Sixteen weeks later their anxiety, and their depression, had fallen far more than with placebo.

In a 2025 trial of 198 adults with generalised anxiety disorder, a single dose of LSD with no therapy at all cut anxiety more than placebo at 100 and 200 µg, though not at 25 or 50; at 100 µg the gap was still there twelve weeks later. The trial was sponsored by the company developing the drug, and its results are meant to guide larger trials.

Why to read these results carefully

A full dose of LSD is hard to mistake for a placebo, and psychedelic trials rarely check whether people could tell what they got, so their benefits are probably overestimated.

Microdosing — taking a fraction of a dose too small to trip — is a different story. When 191 people blinded themselves with look-alike placebo capsules, they improved about as much on placebo as on microdoses.

Risks and staying safe

Physically gentle; the risks are in the mind, in what you do, and in what's really on the paper.

At normal doses of 50–200 µg, LSD is non-toxic. Deaths blamed on it have turned out to be massive overdoses, people restrained face-down, or a different drug. Its safety margin is estimated as among the widest of any drug, though that figure rests on animal data. Psychedelics don't generally lead to addiction, and in a survey of 135,095 adults, psychedelic use wasn't linked to more mental health problems.

The real risks

• A hard trip: The most likely problem, and it can lead to dangerous behaviour. On LSD it can last ten hours or more.
• Not LSD at all: In one analysis, 21 of 70 blotters marked as LSD held 25I-NBOMe, which, unlike LSD, is highly toxic.
• Higher doses: At 200 µg, anxiety becomes significant, with no gain in the good effects.
• Psychosis: Rarely, a trip sets off a prolonged psychotic reaction.
• Lithium: In reports of psychedelics taken on lithium, nearly half described seizures.
• Lasting visuals: Uncommon, but visual disturbances can persist for months or years — reported most after LSD.
• Tolerance: Taken daily, tolerance builds within days, and the tolerance carries over to mushrooms.
• The law: In Canada, LSD is a Schedule III controlled substance.

Set and setting

• Go in calm and open, with a clear intention.
• A safe, familiar place, with someone sober you trust, for the whole of it — most of a day.
• Skip it if you or close family have had psychosis, or if you're on lithium.
• If it gets hard: it does end, and letting go goes better than fighting it.

Check what you know

Five questions about what acid is doing.

• A friend took 100 µg of LSD at 8 pm. At midnight they ask why it isn't wearing off. What's going on? Nothing's wrong: 100 µg typically lasts about eight hours. In a controlled study, 100 µg of LSD lasted 8.2 hours on average.
• One volunteer takes 100 µg of LSD; another takes a strong 30 mg dose of psilocybin. How different are their trips? Very similar — the clearest difference is how long the LSD lasts. The two produced qualitatively and quantitatively very similar effects; LSD lasted clearly longer.
• Someone says: "If 100 µg is good, 200 will be twice as good." What did the dose study find? The good effects topped out at 100 µg; at 200, ego dissolution and anxiety rose. Good drug effects hit a ceiling at 100 µg, and 200 µg brought significant anxiety.
• A blotter is sold as acid. Can you be sure that's what it is? No — some blotters sold as LSD hold NBOMes, which are far more toxic. In one analysis, 21 of 70 blotters marked as LSD contained 25I-NBOMe, linked to seizures and deaths.
• On LSD with eyes closed, someone sees vivid, detailed scenes. What did brain scans find going on? The primary visual cortex was communicating with far more of the brain than usual. Its connectivity rose with many regions, and the more it did, the more vivid the imagery.