There are numerous data on the effects of lithium on the hematopoietic system, especially in aplastic anemia and thrombocytopenia. This case shows a dual effect of therapy with lithium carbonate in a 49-year-old patient with schizophrenic psychosis and idiopathic thrombocytopenia. Lithium was introduced as a therapy firstly in order to augment the existing antipsychotic therapy, and secondly as potential protection against hematopoiesis in order to increase the number of thrombocytes after idiopathic thrombocytopenia had been diagnosed.