Background: Psychosis is a psychiatric disorder in which reality testing and interpersonal relationships in several important functional areas are impaired. Some biochemical disturbances occur during psychotic period. Due to the vital role of serum potassium level on psychotic patients and its effect on cardiovascular system, this study was conducted to investigate serum potassium changes.

  Materials and Methods: A prospective non- Randomized pre/post test study (Quasi-experimental) was conducted on 103 prepared samples obtained from 103 patients hospitalized in Imam Hossein and Taleghani Hospital during 2005-2006 in Tehran. All subjects were initially interviewed in the first day then considering inclusion / exclusion criteria, blood samples were drawn and Brief psychiatric Rating scales (BPRS) were completed by the researcher. The same process was repeated in the day before release. Data were analyzed through Spearman- multiple regression, Paired test, chi-square and Kolmogorov- Smirnov tests.

  Results: BPRS were significantly different in the first and last days of hospitalization (P<0.019) Serum Potassium levels of the first and last days were meaningfully different (P<0.005) there was a negative correlation between the severity of psychosis in the first day and serum potassium level.