Introduction. The establishing of reference intervals is an important task of any clinical diagnostic laboratory. It can be effectively solved using indirect approaches by analyzing the patient database. Objectives. To study the determining possibility of erythrocyte parameter reference intervals based on patient data analysis using the Bhattacharya method. Materials and methods. We used the database of patient samples results obtained using a Sysmex XT-4000i hematology analyzer. Reference intervals Hb, RBC and MCV were investigated using the Bhattacharya method. At the next stage, the records of patients whose results went beyond the obtained reference intervals were excluded from further analysis. After that, RDW-CV, RDW-SD, Hct, MCH, MCHC were analyzed using the standard non-parametric method. This allowed us to exclude the effect of pathological components along the edges of the reference distribution on the results obtained. An Optimization of the sample mean and standard deviation calculation by the Bhattacharya method for use with MS Excel software was proposed. Results. The proposed design of the study allowed us to obtain reference intervals for erythrocyte parameters. We supposed it was reasonable to use only one lower reference limit for the MCHC (5th percentile) and only one upper limit for the RDW (95th percentile). The heterogeneity of the reference distribution of the RDW indices was identified due to the ability of the Bhattacharya method to divide the total sample into Gaussian components. Conclusion. The suitability of the Bhattacharya graphical method for determining reference intervals of erythrocyte parameters as well as the rationality of combining it with standard statistical methods has demonstrated. From a practical point of view, the applied approach was a rational and objective way of establishing working reference intervals for a laboratory of a multidisciplinary hospital, which does not have the potential for mass involvement of healthy outpatients.