The magnetic orientations of human red blood cells (RBCs) in some media such as phosphate buffer solutions (PBS), serum and plasma were investigated to ascertain the behavior of RBCs under strong magnetic fields in the body. The effects of orientation of RBCs in suspensions were measured by changes in the electrical conductivity of suspensions. The electrical conductivity of the suspensions were increased by application of magnetic fields parallel to the electric field. This phenomenon indicates that RBCs are redirected by a magnetic field. The changes in electrical conductivity of samples of 40% RBCs suspended in PBS, serum and plasma were 19%, 9% and less than 4% respectively. The electrical conductivity of anticoagulated whole blood was not changed by application of magnetic fields up to 8 T. Through microscopic observation of RBCs suspended in plasma under 8 T magnetic field, it was revealed that the aggregation of RBCs or rouleau formation occurred in plasma and rouleaux were oriented by the strong magnetic field. The changes in the electrical conductivity of the suspensions and whole blood by the magnetic orientation are prevented by the aggregation and rouleaux formation of RBCs.