Reticulocyte is the cell which subsequently transforms into erythrocyte (oxygen carrier). Reticulocyte also participates in gas transportation, however because of its immaturity the given cells can’t fulfill their function to the full extent. Their number in the healthy body consists of 1 %.

Normally they are produced by bone marrow due to the following reasons: first of all, after erythrocytes’ death with the aim of forming new ones (their life span is approximately 120days, after which they are destroyed in the spleen), secondly when body requires more oxygen (for example during intensive physical load) to increase the number of gas carriers.

Therefore disbalance of mature and immature forms shows the following: - excessive death of erythrocytes - blood loss - decreased hemoglobin level- failure of respiratory organs that causes oxygen deficiency - bone marrow diseases.