Background. Multiple sclerosis (MS) is the most common demyelinating disease of the central nervous system. It mostly affects young people. Pathological changes in MS cause destruction of myelin sheath around axons which impedes transmission of nerve impulses in the central nervous system. The diagnosis of MS is based on clinical evaluation, biochemical tests of blood and cerebrospinal fluid as well as imaging. The study aim was to assess blood counts of MS patients. Materials and methods. The study group comprised 189 people (77 healthy) and 112 MS patients treated at the Department of Neurology at the Medical University in Lublin. Whole blood parameters were determined on the Advia 2120 i analyzer. Statistical analysis was made using the Statistica 12.5 program. Results. Patients evaluated with regard to clinical condition and stage of disease demonstrate differences in RBC count, hemoglobin, hematocrit and red blood cell volume (MCV). RBC count of patients with relapsing-remitting MS (RRMS) was lower (Me = 4.73 million/μl) than for patients with secondary progressive MS (SPMS) (Me = 5.03 million/μl). Additionally, differences in hemoglobin were observed between RRMS patients (Me = 13.9 g/dl) and SPMS patients (Me = 14.7 g/dl). Significant differences were also observed for hematocrit; (Me = 40.5%) for RRMS patients and (Me = 44%) for SPMS patients. Differences in MCV between the examined groups of MS patients and the control group were not statistically significant. The same referred to differences in WBC count; (Me = 6.95 thousand/μl) for MS patients and (Me = 6.59 thousand/μl) for control group as well as platelet count; (Me = 237.5 μs/μl) for SM patients and (Me = 252 thousand/μl) for control group. Conclusion. Analysis of blood parameters reveals significant differences between MS patients and control as well as differences between RRMS and SPMS patients with regard to red blood cell system. An in-depth analysis also in terms of disease duration and stage of clinical advancement may be a valuable source of information on the overall health condition of MS patients.