Metabolic disorders, especially diabetes mellitus, occur more often in patients diagnosed with psychiatric diseases than in the general population. The suggested reasons include common environmental factors, like a lifestyle leading to obesity and insulin resistance, social and economic status. Moreover, these disorders partially share a common genetic background. The influence of antipsychotic therapy itself also plays an important role. An increased risk of metabolic disorders, like glucose dysregulation, dyslipidemia or weight gain, exists during antipsychotic treatment. These drugs influence the hypothalamic regions controlling food intake, impair the insulin release by beta cells or induce insulin resistance. Therefore the choice of antipsychotic drug should be dependent on the actual patient's metabolic status and his comorbidities. Patients treated with antipsychotics should be screened for several metabolic disorders. Periodic checks for abnormalities of body weight, waist circumference, blood glucose or lipid profile are recommended in these patients. Any abnormality noticed during such a check is the indication for antipsychotic treatment modification and adequate metabolic disorder treatment.