Most psychedelics leave your body surprisingly fast, often within 24 to 48 hours, making them difficult to detect on standard drug tests. The exact window depends on which substance you took, what type of test is being used, and individual factors like kidney function and genetics. Here’s a breakdown for each major psychedelic.
Psilocybin (Magic Mushrooms)
Psilocybin is one of the fastest psychedelics to clear your system. Your body converts psilocybin into its active form, psilocin, which produces the psychedelic effects. Psilocin is then filtered out through your kidneys.
In blood, psilocybin and psilocin are detectable for up to about 15 hours after ingestion. In urine, the detection window is roughly 24 hours. Hair tests can pick up past use for up to 90 days, but hair testing for psilocybin is uncommon and not part of any standard screening panel.
Kidney function plays a major role in how quickly psilocin clears. Clinical trials studying psilocybin typically exclude people with impaired kidney function because the substance can accumulate when the kidneys aren’t filtering efficiently. Genetic differences in liver enzymes, particularly the ones responsible for breaking down psilocin, also create significant person-to-person variation in how fast the drug is processed.
LSD (Acid)
LSD is active at extraordinarily small doses, measured in millionths of a gram, which makes it one of the hardest drugs to detect. After a single dose, blood concentrations drop in two phases: an initial half-life of about 3.6 hours for the first 12 hours, then a slower terminal half-life averaging around 9 hours. In a pharmacokinetic study, LSD was measurable in blood plasma in all subjects up to 12 hours, in most subjects up to 16 hours, and in about half of subjects up to 24 hours.
Urine testing for LSD targets a breakdown product called O-H-LSD, which sticks around longer than LSD itself and reaches higher concentrations. Even so, detection windows are short compared to most drugs. Standard workplace drug panels do not include LSD. Specialized tests can find it, but only if someone is specifically looking for it within a day or two of use.
MDMA (Ecstasy, Molly)
MDMA stays in your system longer than most classic psychedelics. In oral fluid (saliva), MDMA is detectable for roughly 47 hours after a dose, with its metabolite MDA detectable for about 29 hours. Some samples have tested positive as far out as 71 hours for MDMA and 47 hours for MDA. MDMA appears in saliva within 15 minutes to just over an hour after taking it.
Unlike LSD and psilocybin, MDMA is included on federal workplace drug testing panels. The federal cutoff for an initial urine screening is 500 ng/mL, with a confirmatory test threshold of 250 ng/mL. For oral fluid tests, the initial cutoff is 50 ng/mL with confirmation at 25 ng/mL. These are the levels your sample needs to exceed to count as a positive result. Because MDMA is structurally related to amphetamines, it can also trigger a positive result on standard amphetamine immunoassays.
DMT
DMT is the shortest-acting psychedelic and clears the body extremely quickly. When smoked or injected, the effects peak within about 5 minutes and are completely gone within 30 minutes. Blood concentrations peak at 10 to 15 minutes and become essentially undetectable within one hour.
When taken as ayahuasca (a tea that includes a plant-based enzyme inhibitor to slow DMT’s breakdown), the effects last longer, peaking around 90 minutes and lasting up to 4 hours. Even so, DMT is rapidly eliminated. Animal studies show that no traces of DMT or its metabolites remain in urine after 24 hours, though tiny residual amounts (0.1% of the initial dose) have been detected at 2 and 7 days in tissue. DMT is not part of any standard drug test panel.
Mescaline (Peyote, San Pedro)
Mescaline has a longer detection window than most psychedelics. Its half-life in humans is about 6 hours, and its effects can last 10 to 12 hours. Your body excretes a large portion of mescaline unchanged through urine, with studies showing anywhere from 28% to 81% leaving the body in its original form. The primary metabolite is eliminated steadily, with 87% cleared within 24 hours and 96% within 48 hours.
Despite this relatively predictable clearance, mescaline is rarely detected in practice. Assays for measuring mescaline levels are not widely available, and the substance does not appear on routine drug panels. Intoxication cases are almost always diagnosed based on symptoms and self-reported use rather than lab confirmation.
Why Standard Drug Tests Usually Miss Psychedelics
The standard federal workplace drug test screens for five categories: amphetamines, cannabinoids, cocaine, opioids, and PCP. MDMA was recently added as a distinct analyte under the amphetamine category, but LSD, psilocybin, DMT, and mescaline are not on the panel. Detecting these substances requires specialized testing that employers or courts would need to specifically request, which is uncommon and expensive.
Even when specialized tests are ordered, psychedelics are challenging targets. Many are active at doses so small that they fall below the detection limits of standard immunoassay screening. More sensitive laboratory techniques can detect substances at concentrations below 0.5 ng per sample, but these methods are typically reserved for forensic investigations, not routine employment screening.
Factors That Affect How Long They Stay
Your individual clearance rate depends on several overlapping factors. Kidney function is the most important for psilocybin, since psilocin is primarily eliminated through urine. People with reduced kidney function will clear the substance more slowly.
Liver enzyme activity matters across the board. The enzymes responsible for breaking down psilocin (and many other psychedelics) vary significantly between people due to genetic differences. Some people are rapid metabolizers who process substances quickly, while others are slow metabolizers who may retain them longer. Medications that inhibit or activate these same liver enzymes can also shift the timeline. The dose you took, the route of administration (oral versus smoked versus injected), and your body composition all contribute as well.
False Positives to Be Aware Of
If you’re taking certain prescription medications, you could test positive for LSD even without having used it. Documented false positives for LSD have occurred in patients taking trazodone, sertraline, fluoxetine, amitriptyline, buspirone, haloperidol, risperidone, and several other psychiatric medications. These false positives happen because immunoassay screening tests can cross-react with structurally similar compounds. A confirmatory test using more precise laboratory methods will rule out a false positive, so if you receive an unexpected result, requesting confirmation testing is the appropriate next step.