The aim of this investigation is to search for the possibility of terahertz (THz) spectroscopy in combination with dielectrophoresis for studying erythrocytes from patients with diffuse liver diseases for diagnostics and differentiation of liver fibrosis degrees. Seventy-nine men aged 33 to 67 years with diffuse liver pathology, mainly alcohol, viral, and mixed genesis with varying degrees of liver fibrosis, were included in the study with 30 men (31- to 64-year-old) without signs of pathology of internal organs and liver fibrosis (F0, first group). The study of suspensions of red blood cells was carried out by THz spectroscopy and dielectrophoresis. An increase in the degree of liver fibrosis was associated with an increase in the number of deformed cells prone to aggregation and destruction, with a reduced surface charge, thickened membranes with high electrical conductivity, low deformability on the background of high summarized viscosity, and rigidity indicators (p  <  0.0001 to 0.05). Strong correlations of THz spectroscopy indices with electrical and viscoelastic parameters of red blood cells were obtained. The revealed possibilities of the study of blood and its cell components are very promising in the diagnosis and differentiation of the degrees of liver fibrosis.