Direct Current (DC) is widely used in electrotherapy for disease treatment, with typical studies on the effect of DC on disease factors in the blood. The objective of this work was to study the effects of DC on human blood, and to determine the intensity of DC that safely flows through blood, and to know which components of blood are most affected by DC. The effects on the counts or levels of main blood components [Red Blood Cells (RBCs), White Blood Cells (WBCs), Platelets (PLTs), Hemoglobin (Hb), and Hematocrit (Hem)] were considered. DC intensities from 1 to 10 mA were passed through blood samples of ten healthy persons for periods of up to one hour. A blood test (blood count with white blood cell differential) was carried out before DC flow and after 5, 10, 15, 30, 45, and 60 minutes of treatment.