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Erythrocytes
Medical expert of the article
Last reviewed: 05.07.2025
The number of red blood cells (RBC) in the blood is one of the most important indicators of the blood system. The erythrocyte is the most numerous formed element of the blood, containing hemoglobin. It is formed from the reticulocyte upon its exit from the red bone marrow, the final transformation of the reticulocyte into a mature erythrocyte occurs within a few hours. The erythrocyte has the shape of a biconcave disk, which ensures the maximum ratio of "surface area/volume". The diameter of a mature erythrocyte is 7-8 μm (deviations within the range from 5.89 to 9.13 μm - physiological anisocytosis).
A decrease in the number of red blood cells is one of the criteria for anemia. The degree of erythrocytopenia in various anemias varies widely. In iron deficiency anemia due to chronic blood loss, the number of red blood cells may be normal or moderately reduced - 3-3.6×10 12 /l. In acute blood loss, B 12 -deficiency anemia, hypoplastic anemia, hemolytic anemia after a hemolytic crisis, the number of red blood cells in the blood may decrease to 1-1.6×10 12 /l, which is considered an indication for emergency treatment. The number of red blood cells, in addition to anemia, decreases with an increase in the volume of circulating blood - pregnancy, hyperproteinemia, hyperhydration.
An increase in the number of red blood cells in the blood - erythrocytosis (more than 6×10 12 /l in men and 5×10 12 /l in women - is one of the characteristic laboratory signs of erythremia. Erythrocytosis can be absolute (an increase in the mass of circulating red blood cells due to increased erythropoiesis) and relative (due to a decrease in the volume of circulating blood).
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