microdosenoun [ C ]
uk/ˈmaɪ.krəʊ.dəʊs//ˈmaɪ.kroʊ.doʊs/an extremely small dose (= measured amount) of a medicine or drug:
In homoeopathy, illnesses are treated using highly diluted forms of herbs and minerals, known as microdoses, that in higher quantities could give rise to the same problems as those that are being treated.