Schizophrenia is a chronic mental disorder. It is treated with antipsychotics, which have a high risk of adverse reactions. One of these adverse reactions is metabolic syndrome, which increases the risk of cardiovascular diseases and the mortality rate of patients with schizophrenia. Various studies have shown an association between hematological parameters and metabolic syndrome. In this regard, the use of hematological predictors as a diagnostic tool can help identify risks and timely correct antipsychotic therapy for preventing metabolic syndrome. One of the most promising predictors are hematological inflammation coefficients obtained on the basis of a clinical blood test. The neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), and the index of systemic immune inflammation (SII), are inexpensive, easy-to-detect markers of systemic inflammation. This case report of a 48-year-old female patient with paranoid schizophrenia, hematological inflammation coefficients were increased during antipsychotic therapy compared to the baseline. At the start of clozapine therapy, the highest levels of systemic inflammatory markers were recorded, after which the patient developed metabolic syndrome. In this case, stopping clozapine therapy when the level of hematological inflammatory coefficients increases would prevent the development of metabolic syndrome in the patient. Markers of systemic inflammation can help doctors diagnose metabolic syndrome early. This may reduce rates of cardiovascular disease and type 2 diabetes and thus reduce mortality in patients with schizophrenia. This case report demonstrates that wider implementation of hematological predictors of metabolic syndrome into real clinical practice could help significantly improve the safety of antipsychotic therapy.