Risks of Microdosing: What Canadians Should Know in 2027

A microdose is small, and that can make it easy to assume it’s risk-free. It isn’t. Psilocybin is a pharmacologically active substance and a controlled drug in Canada, and it’s always worth asking any seller exactly what is in a product and how it is checked.

None of that is a reason for panic. It’s a reason to know the picture before you decide anything.

This page covers the wider risks for Canadians: the health questions, who should avoid psilocybin altogether, the medicines it can interact with, where the law stands, what can go wrong with an unregulated product, and practical ways people lower the risk. If you’re looking for what a microdose day can feel like and how to handle unwanted effects, our guide to psilocybin side effects covers that side in detail.

What the research can and can’t tell you

The honest starting point is that the evidence is thin. A 2025 systematic review in Neuropharmacology gathered 31 studies and two clinical case reports on microdosing LSD and psilocybin. It found side effects were usually dose-dependent, mild and short-lived, with raised blood pressure, anxiety and cognitive impairment among the most common.

The same review points out its own limits: studies reported side effects in different ways, and most ran for only a short time. That matters, because many people who microdose do it for months.

Health Canada says no studies have yet evaluated the long-term effects of repeated magic mushroom use. The Centre for Addiction and Mental Health describes the limited research on microdosing as having produced mixed results.

So anyone calling microdosing “totally safe” or “dangerous” is claiming more than anyone knows. What we do have is a handful of specific, well-grounded concerns.

Heart and blood pressure

Health Canada lists increased heart rate and blood pressure among the physical effects of magic mushrooms, and notes that for people with heart disease, those short-term effects could potentially be harmful.

The 5-HT2B question

Some medicines that strongly stimulate a receptor called 5-HT2B have been linked to heart-valve damage, known as valvulopathy. The appetite suppressant fenfluramine is the best-known example.

A 2024 review in the Journal of Psychopharmacology notes that psilocin, the form psilocybin takes in the body, likely stimulates that receptor at doses people feel. It asks whether regular microdosing over months could mean chronic stimulation of the same receptor.

The authors call that risk uncertain. They also say no controlled studies have checked heart valves in long-term microdosers, and they call for exactly those studies. This is an open question, not a settled harm.

For one group, it changes the conversation. If you have a heart condition — a valve issue, a murmur you’ve been told about, cardiomyopathy, high blood pressure, or anything a cardiologist follows you for — talk to your clinician before you consider psilocybin. Ask them about the 5-HT2B question directly; it’s a fair, specific question and it gives them something concrete to consider.

Mental health risks

Health Canada says people who have, or are predisposed to, psychiatric conditions may face a higher risk of side effects, and that this association is still being evaluated.

The U.S. National Center for Complementary and Integrative Health is more direct. It says psilocybin is not safe for people with psychotic conditions such as schizophrenia or schizoaffective disorder, or for people with severe bipolar disorder or borderline personality disorder.

Published case reports of psilocybin-induced psychosis follow a pattern. A 2024 case report and review describes these episodes occurring mainly in people with a past psychiatric history who had taken large or repeated doses. It also notes that people with risk factors for psychosis are typically excluded from psilocybin studies, so there’s little research on them at all.

That gap is the point. If you have a personal or family history of psychosis or bipolar disorder, no study shows a microdose is fine for you, and there are good reasons for caution.

For people without that history, the more common psychological effects, and how people handle them, are covered in our side effects guide.

Who should avoid psilocybin

Putting the evidence together, these are the people who should avoid psilocybin, or at the very least not consider it without a clinician’s input:

• People with a psychotic condition, such as schizophrenia or schizoaffective disorder, or with severe bipolar disorder or borderline personality disorder, as NCCIH lists.
• People with a family history of psychosis or bipolar disorder. People with risk factors for psychosis are typically excluded from studies, so the risk to them is largely unknown.
• People with heart disease, including valve problems and high blood pressure, for the reasons above.
• Anyone pregnant or breastfeeding. MotherToBaby says studies have not been done on magic mushrooms and miscarriage, birth defects or other pregnancy problems in humans, and that they haven’t been studied during breastfeeding.
• Anyone taking a medicine that interacts with psilocybin, especially lithium, an MAOI or tramadol, unless their prescriber has looked at it. More on that below.

If you’re not sure whether something in your history counts, ask a doctor or pharmacist first.

Drug interactions

Psilocybin works through the brain’s serotonin system, so it can meet other medicines that do the same. We cover this in depth in our guide to psilocybin and drug interactions; here is the short version.

SSRIs and SNRIs

In a 2023 Johns Hopkins survey of more than 600 reports of people taking psilocybin mushrooms while on an antidepressant, effects were weaker than expected in 47% of reports involving SSRIs and 55% involving SNRIs. Weaker effects are not a reason to take more.

Serotonin syndrome is the serious concern. A 2022 review of serotonin toxicity and psychedelics found serotonergic medicines without an MAOI are low-risk alongside psychedelics, but low risk isn’t no risk. Your prescriber can say how this applies to your medicine.

MAOIs

MAOIs are the class of most concern. The same review found that true serotonin toxicity typically involves an overdose or a combination that includes an MAOI. If you take one, treat psilocybin as a combination to avoid.

Lithium

This is one of the clearest warning signs in the whole field. A 2021 Johns Hopkins analysis of online experience reports found that 47% of 62 reports of lithium combined with a classic psychedelic involved seizures. Most involved LSD rather than psilocybin, and the researchers called their conclusion provisional, but anyone on lithium should talk to their prescriber before doing anything at all.

Tramadol

Tramadol also acts on serotonin. A clinical review describes seizures and serotonin syndrome as its two significant adverse reactions, more likely when other drugs, particularly antidepressants, are taken alongside it. If you take it, raise it with your prescriber or pharmacist.

Alcohol, cannabis and other drugs

Health Canada says using magic mushrooms with substances such as cannabis, amphetamines or alcohol raises the risk of serious side effects and adverse events.

One rule matters more than any of the details: keep taking your prescribed medication. Nothing in a microdosing practice — nothing in this article, nothing you read on any forum — is a reason to stop or change a medication on your own. Stopping a medicine abruptly carries real risks; a conversation with your prescriber doesn’t.

The legal position in Canada

Psilocybin is illegal in Canada outside a few narrow exceptions. Psilocybin and psilocin are both listed in Schedule III of the Controlled Drugs and Substances Act, and Health Canada states that the production, sale and possession of magic mushrooms are illegal in Canada. That applies in every province and territory, and a smaller dose doesn’t change it.

What the penalties look like on paper

For a Schedule III substance, possession carries up to three years in prison when prosecuted as an indictable offence (section 4). Trafficking carries up to ten years, and under the Act, trafficking isn’t limited to selling. It also covers giving, transferring, sending or delivering (section 5). Sharing with a friend counts. These are maximums, not predictions; courts decide sentences case by case.

Storefronts and websites

Shops selling psilocybin operate in several Canadian cities, and some have been raided by police. In Vancouver, for example, police raided three magic mushroom dispensaries in November 2023, as Global News reported. A shop being open can make psilocybin look legal. It isn’t. A storefront tells you something about local enforcement, not about the law. The Centre for Addiction and Mental Health notes that selling or buying psychedelics online is illegal too.

The narrow legal routes

Health Canada describes three: clinical trials; the Special Access Program, through which a practitioner can request a drug for a patient with a serious or life-threatening condition; and individual exemptions under section 56 of the Act, granted at the health minister’s discretion. Each is case by case, and none covers general wellness use or a store.

Driving

Under the Criminal Code, it’s an offence to drive while your ability is impaired to any degree by a drug.

Calling for help

If someone has a life-threatening reaction to a drug, call 911. The Good Samaritan Drug Overdose Act, law since May 4, 2017, added section 4.1 to the Act. Under it, the person who calls, and anyone still at the scene when help arrives, isn’t to be charged with or convicted of possession based on evidence found because of that call. It also covers breaches of pre-trial release, probation, conditional sentence or parole conditions about simple possession. It covers possession only, not selling or growing, but it exists so that nobody hesitates to call.

For the full picture, including the penalties, the diversion rules for simple possession and the bill now before Parliament, see our guide to psilocybin legality in Canada.

Unregulated-supply risks

Psilocybin sold outside Health Canada’s legal routes isn’t covered by any official testing or standards, so some risks come from the supply itself.

Strength varies

Health Canada notes that the strength of magic mushrooms can vary greatly, and that one mushroom may contain different amounts of the active ingredients than another. With a microdose, that matters. A batch stronger than you expected can turn a sub-perceptual dose into a noticeable one, and Health Canada notes that a “bad trip” may occur, particularly at high doses.

Wild mushrooms can be mistaken

Many mushroom species look alike. Health Canada warns that people can eat poisonous mushrooms by mistaking them for magic mushrooms, and NCCIH notes that such a mix-up could lead to fatal poisoning. Picking your own is the highest-risk way to get them.

Products may not contain what the label says

Health Canada warns that illegally produced drugs are not tested and may contain other dangerous substances. This is why it helps to ask any seller what is in a product and how it is checked.

Ways to lower the risk

No approach removes the risks above. These are the habits people use to keep them smaller.

Check your medicines first

Make a full list of what you take, including over-the-counter medicines and supplements, and show it to your prescriber or pharmacist before you start. Pharmacists check interactions every day, and you can usually talk to one without an appointment.

Know exactly how much you’re taking

Choose products that state the amount per capsule or piece, and measure carefully if you use dried mushrooms. Start at the low end. Our dosing guide explains what people mean by a microdose and how common schedules work.

Never pick wild mushrooms to eat

Unless you are an expert in identifying mushrooms, the lookalike risk isn’t worth it.

Don’t mix

Keep alcohol, cannabis and other drugs out of a dose day, for the reasons Health Canada gives above.

Keep it off the road

Don’t drive or operate machinery on a dose day, especially early on, while you’re still learning how a dose affects you.

Build in breaks

Most protocols include off days, partly because Health Canada notes tolerance can build with regular use.

Keep honest notes

A one-line note each day on the dose, your mood and your sleep gives you something firmer than memory.

Tell someone

Let a person you trust know what you’re doing, especially in the first weeks.

Know when to get help

In an emergency, such as a seizure or someone who can’t be woken, call 911. If you’re unsure, Canada’s poison centres, available around the clock, can be reached at 1-844-POISON-X (1-844-764-7669); in Quebec, call the Centre antipoison du Québec at 1-800-463-5060. If you’re in crisis, you can call or text 9-8-8, the Suicide Crisis Helpline. The side effects guide lists the warning signs in more detail.

Where Kind Stranger stands

Plenty of Canadians are curious about microdosing, and we think that curiosity deserves honest information rather than hype or scare stories. That includes being clear that the risks are real and that microdosing is not a substitute for professional care.

If you’re looking at products, our product pages list ingredients and amounts. Holiday, for example, is a capsule of 125 mg Golden Teacher mushroom with 100 mg passionflower extract. If you take any prescription, show that ingredient list to your prescriber or pharmacist before adding anything new.

Frequently asked questions

Is a microdose less risky than a full dose?

In some ways, yes: the 2025 review found side effects were usually dose-dependent. But the microdosing studies it gathered were mostly short, much of what’s known about interactions and psychosis comes from larger doses and case reports, and nobody has studied the heart over months of regular use. A small dose isn’t a reason to skip the checks above.

How often do people microdose?

Most follow a schedule with a dose every two or three days and off days built in. There’s no single protocol that research has settled on. An overview of common schedules lives in our dosing guide.

Can I microdose while taking antidepressants?

This is a question for your prescriber, not the internet. Don’t stop your medication to microdose — that’s the one clear don’t here. Bring it up honestly with the person who prescribes it, and follow their advice.

Is it legal to order psilocybin online in Canada?

No. Buying online is still buying a controlled substance, and having it mailed to you doesn’t change that. Bringing psilocybin into Canada from another country is a separate offence under section 6 of the Act.

This article is general information, not medical or legal advice. Talk with a qualified clinician about your own health — and never stop a prescribed medication without their guidance.