Psilocybin glossary: terms from calculators, lab reports and studies

How to use this glossary

Terms are grouped by first letter; tap a letter to jump. Each definition names the study, rule or agency behind its facts, numbered to the sources at the end. For the chemistry in more depth, read psilocybin vs psilocin; for lab reports, see what the mg on a capsule label means.

0-9

4-AcO-DMT

4-acetoxy-N,N-dimethyltryptamine, a synthetic relative of psilocin. Colorado treats any 4-AcO-DMT in a natural medicine product as a failed test.¹ Six of 8 mushroom gummies bought at Portland, Oregon smoke and vape shops contained it.²

5-HT2A receptor

A serotonin receptor in the brain. Psilocin produces psychedelic effects by acting on it.³ See receptor occupancy.

A

Aeruginascin

A minor tryptamine, a trimethylammonium analogue of psilocybin, whose structure was reported in 2006 from the mushroom Inocybe aeruginascens.⁴ Colorado's required lab panel includes it.¹

B

Baeocystin

Psilocybin with one fewer methyl group (4-phosphoryloxy-N-methyltryptamine), first described in 1968 from Psilocybe baeocystis.⁵ Without its phosphate it becomes norpsilocin.⁶

Batch (or lot)

A quantity of product made or harvested together and tested as one unit. Oregon tests every batch for potency, and Colorado tests each harvest lot.^{7, 1} A lab report covers only the batch it names.

Bluing

The blue color where a psilocybin mushroom is bruised: the mushroom's enzymes turn psilocybin into psilocin and oxidize it into blue chains.⁸ A 1982 study of 20 species found no correlation between bluing and psilocybin or psilocin levels.⁹

C

Certificate of analysis (COA)

A lab's report on a sample from one batch: lab, batch number, dates, compounds, method, units and results. In Oregon, the product information document that goes with each product must include its potency test results.⁷ See capsule labels for questions to ask of one.

Cmax

The peak concentration a drug reaches in the blood. A 2025 review reported that one trial found no correlation between psilocin Cmax and body weight, BMI or age.¹⁰

Colorado natural medicine program

Colorado's state-regulated system. Its Natural Medicine Division licenses healing centers, manufacturers and testing facilities, and listed 11 standard and 36 micro healing centers as of October 16, 2026.¹¹ Sessions take place with a licensed facilitator, at a licensed healing center or another location the rules authorize;¹ psilocybin remains illegal under federal law.¹²

Contraindication

A condition or medicine that makes a treatment inadvisable. Research safety guidelines flag a personal or family history of psychotic disorders, and chronic lithium or tricyclic antidepressant use.¹³ See who should avoid psilocybin.

Cross-tolerance

Tolerance to one drug that carries over to another. In a 1961 study of 19 volunteers, people made tolerant to LSD were "to a considerable degree, also cross tolerant to psilocybin", and the reverse.¹⁴

Cubensis

Short for Psilocybe cubensis, the only species Oregon's licensed program allows.⁷ A 2026 study compared 14 of its named strains under identical conditions.¹⁵

D

Decriminalization

Reducing penalties or making enforcement a low priority without making a drug legal. Denver's 2019 Initiated Ordinance 301 made adult personal use and possession of psilocybin mushrooms the city's "lowest law-enforcement priority"; psilocybin stayed illegal.¹⁶

Dry weight

A result stated per gram of dried material, the basis of most potency data on this site. Oregon tells labs not to adjust compliance results for moisture.¹⁷

F

Fireside Project

A free, confidential psychedelic peer support line: call or text 62-FIRESIDE (623-473-7433), 11 a.m. to 11 p.m. Pacific every day. It isn't a suicide hotline; for emergencies it directs people to 911, and for suicidal thoughts to 988.¹⁸

Fixed dose

Giving every trial participant the same amount regardless of body weight. A pooled analysis of 288 people found weight didn't predict the strength of effects.¹⁹

Flush

One wave of mushrooms from a culture. In a 1982 study of P. cubensis, psilocin was generally absent in the first flushes and highest by the fourth, while psilocybin showed no trend.²⁰

G

Glucuronidation

One of the body's two main routes for clearing psilocin, alongside conversion to 4-HIAA: UGT enzymes attach glucuronic acid so the kidneys can excrete it, UGT1A10 likely in the gut and UGT1A9 after absorption.^{21, 3} Studies differ on which route handles more.^{3, 10}

H

Half-life

The time it takes for a drug's blood level to fall by half. For free psilocin, published studies report averages from 1.23 to 4.72 hours.¹⁰

Homogenized

Ground and mixed into one uniform powder so a test sample represents the batch. Oregon has labs homogenize a composite of whole mushrooms before testing.¹⁷

HPPD

Hallucinogen persisting perception disorder: persisting, distressing reoccurrence of drug-like perceptions after a hallucinogen. In controlled studies with 142 healthy people, 13 reported reoccurring drug-like experiences; none met the criteria for HPPD.²²

L

Limit of detection (LOD)

The smallest amount a lab method can reliably detect, so a result below it means "not detected", not zero. In the 14-strain study, norpsilocin and norbaeocystin were mostly below it.¹⁵

Lithium

A mood stabilizer. Of 62 online reports of lithium combined with a classic psychedelic, 47% described seizures and 39% involved medical attention.²³ Don't stop or change lithium without your prescriber; see the interaction reference.

M

MAOI

Monoamine oxidase inhibitor, a class of antidepressants. True serotonin toxicity typically follows a serotonergic drug overdose, or a serotonin-raising drug combined with an MAOI.²⁴

MEQ30

The 30-item revised Mystical Experience Questionnaire, used in psilocybin studies to rate mystical-type experiences. It was validated with pooled data from 184 participants in five lab studies.²⁵

Microdose

The research term for a sub-perceptual amount: one meant to be too small to change perception noticeably. A 2024 review of 19 placebo-controlled studies concluded "it is not yet possible to determine whether microdosing is a placebo."²⁶ See microdosing research.

N

Norbaeocystin

A psilocybin relative with no methyl groups on its nitrogen (4-phosphoryloxytryptamine), described alongside baeocystin in 1968.⁵ Colorado's required lab panel includes it.¹

Norpsilocin

4-hydroxy-N-methyltryptamine, the dephosphorylated form of baeocystin, first reported as a natural product of P. cubensis in 2017.⁶

O

Oregon Psilocybin Services

Oregon's regulated program, created by Ballot Measure 109 in November 2020 (now ORS 475A). Clients receive psilocybin at licensed service centers with licensed facilitators.²⁷ Psilocybin remains illegal under federal law.¹²

P

Placebo

An inactive substance given in place of the drug so researchers can separate drug effects from expectation. In a microdosing study completed by 191 people, the placebo group improved too, with no significant difference between groups.²⁸

Poison Control

The national Poison Help line, 1-800-222-1222, which connects callers to their local poison center 24/7 in over 100 languages.²⁹

Prodrug

A compound the body converts into the active drug. Psilocybin is a prodrug of psilocin: after it's swallowed, it is "rapidly absorbed and transformed to psilocin".¹⁰

Psilocin

4-hydroxy-N,N-dimethyltryptamine, the active compound.³⁰ It oxidizes easily, which is why bruised mushrooms turn blue.⁸ Federal law spells it "psilocyn".¹²

Psilocybin

4-phosphoryloxy-N,N-dimethyltryptamine, the phosphate-carrying form stored in the mushroom.³⁰ The phosphate protects it from oxidation until an enzyme removes it.⁸

Psilocybin equivalent

Psilocybin plus 1.4 times psilocin: a total in psilocybin terms. Oregon's draft rules call it "the maximum theoretical concentration of psilocybin in the sample". New Mexico's proposed labels require a "total psilocybin equivalent" too, but its rule doesn't give a formula.^{31, 32}

R

Receptor occupancy

The share of a receptor type that a drug is bound to. In a PET study of 8 volunteers, psilocybin produced dose-related 5-HT2A occupancy up to 72%, and intensity correlated with both occupancy and blood psilocin.³³

S

Schedule I

The federal schedule that lists psilocybin and psilocyn among hallucinogenic substances (21 CFR 1308.11(d)).¹² State programs in Oregon and Colorado don't change federal law.

Sclerotia

Hardened masses of fungal tissue sold as "magic truffles" or "philosopher's stones". A 2013 study detected only psilocybin in them, measured on a fresh-weight basis.³⁴

Self-blinding

A study design in which participants follow instructions to mix their own substance with placebo capsules, so they don't know which they're taking. In a 2021 microdosing study, participants guessing correctly could explain the small differences from placebo.²⁸

Serotonin syndrome

The most severe form of serotonin toxicity. Signs needing immediate medical attention include muscle jerking, rigidity, high fever, extreme or swinging vital signs, agitation and seizures: call 911.²⁴

Set and setting

Mindset (mood, expectations, intentions) and environment. In pooled data from 261 volunteers, sessions involving PET scanning predicted anxiety more strongly than dose did.³⁵

SSRI

Selective serotonin reuptake inhibitor, an antidepressant class. In a survey, about half of reports of taking mushrooms with an SSRI described weaker effects.³⁶ Don't stop an SSRI on your own.

Strain

A named line within a mushroom species. There's no comprehensive genetic reference for strain names, and in 14 P. cubensis strains grown the same way, psilocybin varied 9.66-fold.¹⁵

T

Tolerance

A weaker response to a drug after recent use. A 1961 study showed tolerance to psilocybin developed in volunteers, to a lesser degree than tolerance to LSD.¹⁴ See tolerance calculators for what's known about recovery.

Total psilocin

Psilocin plus 0.719 times psilocybin, a total in psilocin terms. Colorado labels call it "Total Psilocin";¹ Oregon calls it "total potential psilocin", "the maximum theoretical concentration of psilocin in the sample".¹⁷

Total tryptamines

The sum of psilocybin, psilocin and relatives such as baeocystin, norbaeocystin, aeruginascin and norpsilocin. In the 14-strain study, totals differed 7.88-fold between strains.¹⁵