Microdosing side effects, and who should not microdose

Microdosing side effects are real, even at doses meant to stay below the threshold of noticeable effects. In surveys, the unwanted effects people report most often include anxiety or restlessness, headaches, nausea or stomach discomfort, disturbed sleep, tiredness and a heightened emotional sensitivity. Many describe these as mild and short-lived, but not everyone does, and some people should not microdose at all: during pregnancy or breastfeeding, with a personal or family history of psychosis or bipolar disorder, with a heart condition, or while taking medication, especially antidepressants or lithium. This article sets out what is reported, what is less certain, and when to stop.

What counts as a side effect when microdosing?

A microdose is intended to be sub-perceptual: no visual changes, no "trip". So a side effect here is any unwanted change you notice on a dose day or the day after, physical or psychological, that you would not otherwise expect.

Three things make this topic harder than it looks.

• Most of the data comes from self-reports. Much of what is known about microdosing side effects comes from online surveys and questionnaires, in which people describe their own experience. That is useful, but it is not the same as a controlled study, and samples are often self-selected. You can browse the published literature yourself on PubMed.
• Expectations work both ways. A placebo-controlled "self-blinding" study by Szigeti and colleagues, published in eLife in 2021, found that expectations played a large role in what participants reported. What applies to positive reports can also apply to negative ones: some unwanted feelings may be linked to anticipation or worry rather than to the substance itself. That does not make them less real to the person experiencing them.
• People react differently. Body weight, individual sensitivity, sleep, stress and the natural variation between truffles all play a part. The same dose can feel different from one person to another, and from one day to the next for the same person. That is why a report from someone else tells you little about how you will react, and why starting carefully matters.

Side effects people commonly report

Reported effect	How people describe it	What you can do
Anxiety, nervousness, restlessness	Feeling "on edge", a racing mind, difficulty settling	Stop for the day; if it recurs, stop and talk to a doctor
Heightened emotional sensitivity	Feelings closer to the surface, being moved or irritated more easily	Note it in a journal; avoid stressful situations on dose days
Headache	Mild to moderate headache on the dose day	Drink water, rest; stop if it keeps returning
Nausea, stomach discomfort	Queasiness, especially shortly after taking the dose	Take it calmly, with a little water or tea; stop if it persists
Disturbed sleep	Difficulty falling asleep, lighter sleep	Take the dose in the morning, never in the evening
Tiredness	Low energy on the dose day or the next day	Note it; allow rest days; reconsider continuing
Noticeable perceptual changes	Colours, sounds or time feeling different	The dose is too high for you: do not drive, reduce or stop
Feeling "off" or unfocused	Feeling scattered, not like yourself	Pause and reassess whether this suits you

Some people notice none of these, some notice one or two, and experiences can change from one dose day to another. None of these effects is a sign that "it's working". They are signals to take seriously and to write down.

Less common, but more serious, concerns

Beyond the effects most often reported, a few risks explain why the list of contraindications exists.

Psychological vulnerability

Psychedelics, including psilocybin, are known to be able to trigger or worsen psychotic or manic episodes in people who are vulnerable to them. That is why a personal or family history of psychosis, schizophrenia or bipolar disorder is a clear reason not to microdose. Independent services such as Drugsinfo.nl by the Trimbos Institute describe these risks for truffles and mushrooms.

Heart and blood pressure

At higher doses, psilocybin can raise heart rate and blood pressure. At microdose level these changes are expected to be small, but not necessarily absent. Some researchers have also raised a theoretical question about long-term, repeated use: psilocybin acts on several serotonin receptors, including one (5-HT2B) that has been linked to heart valve problems with certain other drugs. This has not been established for microdosing, but it is one more reason why people with a heart condition should not microdose, and why structured protocols include regular breaks.

Interactions with medication

Psilocybin can interact with medication, and in particular with drugs that act on serotonin. Antidepressants may change how psilocybin is experienced, and there are published reports of serious reactions, including seizures, when classic psychedelics were combined with lithium (PubMed search). Never combine microdosing with these medicines, and never stop or change a prescribed treatment without your prescribing doctor. We cover this in detail in our article on microdosing and antidepressants.

Who should not microdose

Do not microdose if any of the following applies to you:

• you are under 18;
• you are pregnant, trying to conceive or breastfeeding (see microdosing, pregnancy and breastfeeding);
• you or a close family member have a history of psychosis, schizophrenia or bipolar disorder;
• you have a heart condition, including high blood pressure that is not under control;
• you take medication, especially antidepressants or lithium;
• you are going through an acute crisis or feel mentally unstable;
• you need to drive, operate machinery or take responsibility for others' safety on the dose day.

If you are not sure whether one of these applies to you, talk to a doctor before doing anything.

How to reduce the risk of unwanted effects

For adults who have no contraindications and have spoken to a doctor, a few simple principles limit the risk:

• Start low. For a first time, half a dose (0.5 g) on a calm day, in the morning, with nothing important planned.
• Keep to the indicated dose. Do not increase it to "feel something". Noticeable effects mean the dose is too high for you, not too low.
• Take regular breaks. Rest days between doses and longer breaks between cycles, as in a 2-per-week, 6-week, 2-week-break rhythm, avoid daily use.
• Avoid combinations. No alcohol, cannabis or other substances on dose days; they make unwanted effects more likely and harder to interpret.
• Do not drive or operate machinery on dose days.
• Keep a journal. Writing down sleep, mood, energy and any unwanted effect, on dose days and rest days, helps you see patterns. Our guide to keeping a microdosing journal shows what to note.

When to stop, and when to get help

Stop microdosing and talk to a doctor if:

• unwanted effects keep coming back or last beyond the dose day;
• your sleep, mood or anxiety seem worse over several weeks;
• you feel detached from reality, suspicious or unusually agitated.

Call the emergency number 112 straight away in case of chest pain, a very fast or irregular heartbeat, fainting, severe confusion or agitation, or thoughts of harming yourself. In the Netherlands you can also reach 113 Suicide Prevention free of charge on 0800-0113. If you have taken more than intended or feel unwell during a dose day, our article on what to do if you took too much explains the first steps. For general questions, see our FAQ.

FAQ

Is microdosing safe?

No substance is free of risk, and the long-term effects of repeated microdosing have not been well studied. Some people should not microdose at all, and anyone with a health question should talk to a doctor first.

Can microdosing cause anxiety?

Yes. Anxiety, nervousness and restlessness are among the unwanted effects people report most often. If it happens, stop for the day, and talk to a doctor if it returns.

Can microdosing give you a headache?

Some people report headaches on dose days. Drinking water and resting may make the day easier, but if headaches keep coming back, stop and seek medical advice.

Why do I feel tired after microdosing?

Some people report low energy on the dose day or the day after, sometimes linked to lighter sleep. Take doses in the morning, respect rest days, and reconsider continuing if tiredness persists.

Who should not microdose?

Minors; pregnant or breastfeeding women; people with a personal or family history of psychosis or bipolar disorder; people with a heart condition; and anyone taking medication, especially antidepressants or lithium.