Our hypothesis is that the action of aggregating and disaggregating substances in the blood can be detected and quantified by the Microplate Reader. To ascertain the validity of this hypothesis, we selected two types of blood: one that naturally presents erythrocyte aggregation (pig blood) and the other that does not present aggregation (bovine blood). One important reason for the choice of pig blood is that its erythrocyte aggregation resembles that of human blood. T. infestans saliva was added to the pig blood as a disaggregating substance, while bovine fibrinogen was added to the bovine blood as a substance that promotes erythrocyte aggregation. We investigated the dynamic viscosity (h) of these mammals' blood, of T. infestans saliva and of the absorption (A) by Microplate Reader, carrying out UV-Vis spectrophotometric assays of pig plasma with different concentrations of triatominae saliva and of bovine blood with different concentrations of fibrinogen. Our findings indicate that spectroscopic techniques such as the Microplate Reader complement and expand the study of blood rheology, erythrocyte sedimentation and aggregation.