“Doing acid” means taking LSD (lysergic acid diethylamide), a powerful psychedelic drug that alters perception, mood, and sense of self for roughly 10 to 12 hours. It’s one of the most potent psychoactive substances known, active at doses measured in millionths of a gram. A single experience, commonly called a “trip,” can range from euphoric and deeply meaningful to frightening and disorienting, sometimes within the same session.
How LSD Works in the Brain
LSD is structurally similar to serotonin, one of the brain’s key chemical messengers. When you take it, the drug binds to serotonin receptors, particularly a type called 5-HT2A. Activating these receptors is what triggers the hallucinations, shifts in thinking, and altered sense of time that define the experience. LSD also interacts with dopamine and other receptor systems, but research has firmly established that the 5-HT2A receptor is the one responsible for the psychedelic effects. Blocking that receptor cancels the trip entirely.
What makes LSD unusual, even among drugs that target the same receptor, is the specific way it activates certain signaling pathways inside brain cells. Not every compound that binds to 5-HT2A produces hallucinations. LSD triggers a secondary signaling chain that non-hallucinogenic compounds don’t, which helps explain why such a tiny amount of the substance produces such dramatic effects.
What the Experience Feels Like
Effects begin gradually, typically 30 to 60 minutes after taking LSD. The peak hits between 2 and 4 hours in, then slowly fades over the remaining hours. The full experience lasts 10 to 12 hours, which is significantly longer than most other psychedelics.
The hallmark effects are visual: colors appear more vivid, surfaces may seem to breathe or ripple, and geometric patterns can appear with eyes open or closed. Some people experience synesthesia, where senses blend together, like “seeing” music or “hearing” colors. Time perception warps considerably. Minutes can feel like hours, or an hour can seem to pass in moments.
Beyond the sensory changes, LSD profoundly shifts how you experience your own identity. Many users report that the boundary between themselves and the outside world feels thinner or disappears entirely. Researchers describe this as “ego dissolution,” a state where the ordinary sense of being a distinct “I” weakens or temporarily vanishes. At lower intensities, this might feel like a deep sense of connection to other people or nature. At higher intensities, it can feel like merging with everything around you, sometimes described as “cosmic consciousness.” This can be profoundly moving or deeply unsettling depending on the person and the circumstances.
Emotional effects are equally pronounced. Clinical studies have found that LSD increases feelings of well-being, happiness, closeness to others, openness, and trust. But the drug amplifies whatever emotional state is present, so anxiety, paranoia, and confusion are also possible, especially in uncomfortable environments or anxious mindsets. A difficult experience, often called a “bad trip,” can involve intense fear, loops of negative thinking, or a feeling of losing control.
Physical Effects on the Body
LSD is primarily a mental experience, but it does produce measurable physical changes. Clinical research on healthy volunteers has documented increases in blood pressure, heart rate, body temperature, and pupil dilation. The drug also raises levels of cortisol (a stress hormone) and epinephrine (adrenaline), which is why many people feel physically energized or jittery during a trip. Some users experience nausea, jaw tension, or muscle tremors, particularly during the come-up phase.
In controlled settings, these physical effects have been mild and fully resolved within 72 hours. LSD does not cause overdose deaths in the way opioids or stimulants do. There is no established lethal dose in humans. The primary physical danger comes from impaired judgment during the experience, not from the drug’s direct effects on organs.
Dosage and Potency
LSD is measured in micrograms, a unit one thousand times smaller than a milligram. The threshold dose, the minimum needed to feel any effect, is around 15 micrograms. A common recreational dose falls somewhere between 75 and 200 micrograms, while 300 micrograms is considered a heavy dose with intense effects. For perspective, these amounts are invisible to the naked eye, which is why LSD is typically absorbed onto small squares of paper (called “blotter tabs”), dissolved in liquid, or pressed into tiny pellets.
Because the active amounts are so small, it’s impossible to gauge potency by looking at a tab. Street doses vary widely, and what’s sold as LSD sometimes contains other compounds entirely. One significant risk is NBOMe, a family of synthetic drugs that fit on blotter paper and mimic some of LSD’s effects but can cause seizures, organ failure, and death at high doses. Unlike LSD, NBOMe has a bitter, metallic taste. Reagent testing kits, particularly Ehrlich and Hofmann tests, can help verify that a substance is actually LSD. Ehrlich reagent turns pink or violet in the presence of LSD, while a Marquis test showing an orange or red reaction suggests a potentially dangerous substitute.
Tolerance and Habit Formation
LSD builds tolerance rapidly. Taking the same dose two days in a row produces significantly weaker effects on the second day. Full tolerance can develop after just a few consecutive uses and takes roughly one to two weeks of abstinence to reset. This built-in tolerance makes daily use essentially impractical, which is one reason LSD is not considered physically addictive. It does not produce withdrawal symptoms or compulsive drug-seeking behavior in the way alcohol, opioids, or stimulants do.
Risks and Lasting Effects
The most common negative outcome is a psychologically difficult trip. Intense fear, confusion, or paranoia during a 10-to-12-hour experience can be genuinely traumatic, particularly for someone who wasn’t prepared for the drug’s power or who took it in an unpredictable setting.
A less common but more persistent risk is hallucinogen persisting perception disorder (HPPD), a condition where visual disturbances from the trip continue long after the drug has left the body. Symptoms can include trailing images, halos around objects, flickering in peripheral vision, or visual “snow.” The DSM-5 estimates a prevalence of about 4.2% among hallucinogen users, though this number is debated and likely varies depending on frequency of use and individual susceptibility. HPPD can be temporary or, in rarer cases, persist for months or years.
LSD can also trigger or worsen psychotic episodes in people with a personal or family history of schizophrenia or other psychotic disorders. This risk is not limited to heavy use. A single dose can be enough in someone who is predisposed.
Legal Status
LSD is a Schedule I controlled substance under U.S. federal law, the most restrictive category, classified alongside heroin. Possession carries serious criminal penalties in most jurisdictions. Unlike psilocybin mushrooms, which several U.S. cities and states have moved to decriminalize, LSD has seen almost no decriminalization activity. A few state-level proposals in California, Massachusetts, Missouri, and Vermont have included LSD in broader psychedelic reform bills, but none have passed into law as of 2025.
At the same time, the FDA has granted breakthrough therapy designation for LSD in the treatment of generalized anxiety disorder, signaling that regulators see enough clinical promise to fast-track research. This designation does not change its legal status for personal use, but it reflects a growing body of evidence that LSD, administered in controlled therapeutic settings, may eventually become a prescription treatment for specific mental health conditions.