This page consolidates, in one place, the cautions the literature most often attaches to classic psychedelics: a personal or family history of psychosis, schizophrenia, or bipolar disorder; concurrent serotonergic medications and lithium; an absence of pregnancy and breastfeeding safety data; and a hypothesised cardiac concern from chronic dosing. [1] analysis The risk of chronic psychedelic and MDMA microdosing for valvular heart disease doi:10.1177/02698811231190865 Almost all of these are precautionary, drawn from full doses, trial exclusion criteria, or general pharmacology rather than from microdosing research, [2] Systematic review The emerging science of microdosing: A systematic review of research on low dose psychedelics (1955-2021) and recommendations for the field doi:10.1016/j.neubiorev.2022.104706 which means the right way to read the list is “what the literature flags,” not “a validated screening test.” It is a map of where caution and professional input are warranted — not a tool for clearing yourself, and not medical advice.
This is an education-only consolidation of literature-flagged cautions, not a screening checklist or medical advice. It cannot clear or exclude any individual. Decisions involving psychiatric history, pregnancy, or medications belong with a qualified clinician. Never stop a prescribed medication based on anything here.
How to read a contraindication list
A contraindication, in clinical language, is a situation in which a treatment is generally not recommended because the risk is considered too high. Used carefully, the word is informative; used loosely, it implies more certainty than exists here. In this article, contraindication means a literature-flagged caution category, not a final individualised medical decision. For microdosing specifically, most “contraindications” are not the product of trials that dosed at-risk people and measured harm. They are precautionary inferences — from full-dose data, from how the drug works, or from the simple fact that a group has never been studied.
This is not a checklist where being absent from the list means low risk. It is a map of major categories the literature repeatedly flags, and it cannot clear anyone: it determines nothing about whether psilocybin, microdosing, or any psychedelic use is appropriate for a particular person, which depends on medical history, psychiatric history, medications, dose, context, and supervision.
That distinction shapes everything below. A precautionary contraindication is a reason for caution and professional input; it is not, by itself, a demonstrated microdose-specific risk. And the inverse holds too: the fact that a microdose harm has not been demonstrated in these groups is not evidence that they are safe, because the studies that could show harm have not been done. [2] Systematic review The emerging science of microdosing: A systematic review of research on low dose psychedelics (1955-2021) and recommendations for the field doi:10.1016/j.neubiorev.2022.104706
The consolidated picture
| Caution | Why the literature flags it | Basis | Status |
|---|---|---|---|
| Psychosis / schizophrenia history | 5-HT2A action overlaps systems implicated in psychosis | Mechanism + full-dose, precautionary | Red-flag for self-directed use |
| Bipolar disorder / mania history | Concern about precipitating mania | Trial exclusion + precautionary | Red-flag for self-directed use |
| Lithium | Case reports of seizures with psychedelics | Case reports, full-dose | Red-flag for self-directed use |
| MAOIs | Monoamine breakdown and serotonergic/autonomic uncertainty | Pharmacology | Red-flag for self-directed use |
| Antipsychotics (for psychosis/mania) | 5-HT2A/dopamine modulation plus underlying vulnerability | Pharmacology + the condition treated | Red-flag for self-directed use |
| Other serotonergic medications (SSRIs/SNRIs) | Possible additive serotonergic effects; blunting | Pharmacology, mostly full-dose | Clinician-review category |
| Seizure history | Lower seizure threshold in some medication contexts | Case reports, precautionary | Clinician-review category |
| Major cardiovascular disease / uncontrolled hypertension | Acute blood-pressure and heart-rate rises at perceptual doses | Physiology, precautionary | Clinician-review category |
| Chronic cardiac exposure | Hypothesised 5-HT2B valvular risk | In vitro + analogy, hypothesis | Plausible but unresolved |
| Pregnancy / breastfeeding | No safety data exists | Absence of evidence | Insufficient evidence to certify |
Two tiers run through that table. Clinician-review categories are situations the literature flags as outside the scope of self-directed risk assessment — appropriate to raise with a clinician, not to clear yourself on. Red-flag categories carry a stronger signal: lithium, MAOIs, and antipsychotic use for psychosis or bipolar-spectrum conditions should be treated as red flags for unsupervised use rather than routine “ask your doctor” items, both because of the medications and because of the conditions they treat.
Psychiatric history
The most consistently stated caution is a personal or family history of psychosis, schizophrenia, or bipolar disorder, treated across research settings as a reason these substances are generally avoided and used as standard exclusion criteria in trials. [3] Clinical trial Acute, subacute and long-term subjective effects of psilocybin in healthy humans: a pooled analysis of experimental studies doi:10.1177/0269881110382466 The mechanistic concern — that 5-HT2A agonism could precipitate or worsen psychosis or mania in a vulnerable person [4] Peer-reviewed Psychedelics doi:10.1124/pr.115.011478 — is covered in full on the psychological safety page. The consolidation point here is simply that this caution sits at the top of the list, applies to family as well as personal history, and is a matter for a clinician rather than self-assessment.
Medications
Several medications are flagged for possible interactions: serotonergic antidepressants, lithium, and others. These cautions range from theoretical (additive serotonergic effects) to grounded in case reports (seizures reported when psychedelics were combined with lithium). The drug-by-drug detail belongs to the Interactions cluster, which is the authority, and the drug-interaction safety page frames how to think about it. The one rule that belongs on every page: a possible interaction is a reason to talk to the prescriber, never a reason to stop a medication unsupervised. Abrupt discontinuation of psychiatric medication carries serious risks entirely separate from any psychedelic.
Pregnancy and breastfeeding
This is the clearest example of a caution built on absence rather than evidence. There is essentially no data on microdosing psychedelics during pregnancy or breastfeeding. In medicine, an untested substance in pregnancy is treated as not demonstrated safe, and caution is the default precisely because the studies that would be needed cannot ethically be run the way other studies are. This is absence of evidence, not evidence of harm — and equally not evidence of safety. The responsible reading is that the data gap exists and that any decision here belongs with an obstetric or medical professional.
Cardiac considerations
A more speculative caution concerns the heart. Because classic psychedelics can activate the 5-HT2B receptor, and because chronic 5-HT2B activation by other drugs has caused valvular heart disease, a hypothesis exists that frequent, long-term microdosing could carry a comparable cardiac risk. A detailed analysis concluded this is a potential risk needing further study, with calculated safety margins from typical microdoses larger than those of known valvulopathogens but not negligible. [1] analysis The risk of chronic psychedelic and MDMA microdosing for valvular heart disease doi:10.1177/02698811231190865 This is a hypothesis, not a demonstrated outcome — plausibility, not proven risk — and it is treated carefully on the cardiac and 5-HT2B page.
Why this is a map, not a checklist
It would be convenient to turn the table above into a self-administered screening form: tick the boxes, and if none apply, proceed. That is exactly what this page is not. Each row carries a different kind and strength of evidence, several depend on personal and family history a person may not fully know, and none was validated as a microdosing screening instrument. [2] Systematic review The emerging science of microdosing: A systematic review of research on low dose psychedelics (1955-2021) and recommendations for the field doi:10.1016/j.neubiorev.2022.104706 The value of consolidating the cautions is to show where professional input matters and why — not to provide a green light when the boxes stay empty.
- Most cautions are precautionary
- They derive from full doses, trial exclusions, or pharmacology — not from microdosing trials in the flagged groups. [2] Systematic review The emerging science of microdosing: A systematic review of research on low dose psychedelics (1955-2021) and recommendations for the field doi:10.1016/j.neubiorev.2022.104706
- Pregnancy is a data gap
- No safety data means not demonstrated safe; caution is the default, and the decision is a clinician’s.
- Interactions route to a prescriber
- A flagged interaction means raise it with the doctor, never stop a medication unsupervised.
- A map, not a screening test
- The list shows where caution is warranted; it cannot clear any individual to proceed.
Frequently asked questions
What are the main contraindications for microdosing?
The cautions most consistently flagged in the literature are a personal or family history of psychosis, schizophrenia, or bipolar disorder; concurrent use of certain medications, especially serotonergic drugs and lithium; and an absence of safety data in pregnancy and breastfeeding. [3] Clinical trial Acute, subacute and long-term subjective effects of psilocybin in healthy humans: a pooled analysis of experimental studies doi:10.1177/0269881110382466 Hypothesised cardiac concerns from chronic dosing are an additional area of caution. [1] analysis The risk of chronic psychedelic and MDMA microdosing for valvular heart disease doi:10.1177/02698811231190865 The important framing is that most of these are precautionary and derived from full doses, animal models, or general pharmacology rather than from microdosing studies — so this is a list of what the literature flags, not a validated screening checklist or a verdict on any individual.
Is microdosing safe during pregnancy or breastfeeding?
There is essentially no safety data on microdosing psychedelics during pregnancy or breastfeeding, and that absence is the whole point. When a substance has not been studied in pregnancy, the responsible default in medicine is caution, not an assumption of safety — absence of evidence is not evidence of safety. Pregnancy is therefore treated as a situation where these substances have not been shown to be safe, and decisions of this kind belong with an obstetric or medical professional, not a website. This page does not advise for or against; it states that the data gap exists and is a reason for caution.
Should I stop my medication to try microdosing?
No part of this site will tell you to stop a prescribed medication, and doing so on your own can be dangerous in its own right, independent of any psychedelic. Some medications — certain serotonergic drugs, lithium, and others — are flagged because of possible interactions, but the response to a possible interaction is a conversation with the prescribing clinician, never unsupervised discontinuation. Stopping psychiatric medication abruptly carries real risks of its own. The literature flags interactions so that people raise them with a professional, not so that they self-adjust.
If I am not in one of these categories, does that mean it is safe?
No. The list identifies major caution categories the literature repeatedly flags; it does not certify safety for anyone outside them. Being absent from the list is not a green light, for several reasons: the categories depend on personal and family history a person may not fully know, none was validated as a microdosing screening instrument, and long-term repeated microdosing has barely been studied in anyone. [2] Systematic review The emerging science of microdosing: A systematic review of research on low dose psychedelics (1955-2021) and recommendations for the field doi:10.1016/j.neubiorev.2022.104706 The list is a map of where caution and clinician review clearly apply — not a checklist that clears the people it does not name.