Psychotropic drugs, such as antipsychotics and antidepressants, are widely used substances which can display marked metabolic side effects. Psychiatric patients display increased morbidity and mortality which, besides disease specific factors, may be attributed to metabolic side effects of psychotropic drugs. Commonly observed side effects of antipsychotics are weight gain as well as disturbances in glucose and lipid metabolism. Additionally, antipsychotics have been shown to increase diabetes risk. Also, the use of some of the antidepressant substances is associated with an increased diabetes risk. However, large inter-substance variations have been observed. Conversely, diabetics have an increased risk of depression. Metabolic side effects of psychotropic drugs pose a serious impairment for psychiatric patients and their management can play a pivotal role in therapeutic compliance and success. This review aims to give an overview of metabolic side effects of commonly used psychotic drugs and to give an insight into possible underlying mechanisms.