Iron oxide nanoparticles were developed using solvothermal synthesis and suspended in a physiological fluid constituted by erythrocytes in order to perform studies of flow behaviour in glass microchannels. The main purpose of this work was to study the influence of different iron oxide nanoparticles and magnetic fields in the plasma layer thickness and also the influence of the magnetic field in the area composed of nanoparticles attracted to the wall of the microchannel. The results obtained show that nanoparticles with magnetic characteristics promote the thinning of the plasma layer, in contrast to the behaviour observed with nanoparticles without magnetic characteristics. It was also observed upon application of magnetic fields with different intensities, the plasma layer tend to disappear in some areas depending on the type of particles. Moreover, the area of nanoparticles attracted to the microchannel wall increases with the increase of the magnetic field intensity.