A research paper ranked psilocybin mushrooms as the third safest drug (Nutt et al). All drugs can still be harmful under certain circumstances.
The strength of shrooms can vary somewhat, because you are consuming the shrooms themselves, not just the active agents. Different strains have different strengths and potency can somewhat decline over time.
The most common variety of mushroom available is psilocybe cubensis, which we sell is a fairly strong strain and a typical dose of recently dried psilocybe cubensis mushrooms is about 3.5 grams (1/8th of an ounce).
It is not possible to overdose on mushrooms. However, taking a dose that’s different than anticipated can cause temporary anxiety. Interestingly, this can happen if the dose is smaller than expected, as well as if it is larger. In fact, some therapists recommend starting with a fairly strong dose of mushrooms that will quickly move people past their own psychological frameworks and into a more spiritual state, thereby bypassing anxiousness. Other research has suggested that starting with a small initial dose and increasing in successive sessions reduces potential anxiety.