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Number of Red Blood Cells in the Blood

Number of Red Blood Cells in the Blood:

As the blood moves throughout the body, it circulates about 20 – 30 trillion red blood cells (RBCs). Even a small drop of blood (1.0 mm3) image descriptioncontains millions of RBCs:

  • 4.2 – 5.4 million RBCs/mm3 in males
  • 3.6 – 5.0 million RBCs/mm3 in females
Animation showing magnified view of a drop of blood containing a normal RBC count.
Animation showing magnified view of a drop of blood containing a normal RBC count.
Animation showing magnified view of a drop of blood containing a normal RBC count.
Animation showing magnified view of a drop of blood containing a normal RBC count.
Animation showing magnified view of a drop of blood containing a normal RBC count.
Animation showing magnified view of a drop of blood containing a normal RBC count.
Animation showing magnified view of a drop of blood containing a normal RBC count.
Animation showing magnified view of a drop of blood containing a normal RBC count.
Animation showing magnified view of a drop of blood containing a normal RBC count.
Animation showing magnified view of a drop of blood containing a normal RBC count.
Animation showing magnified view of a drop of blood containing a normal RBC count.
Animation showing magnified view of a drop of blood containing a normal RBC count.
Magnified view of a drop of blood containing WBCs, platelets, and a normal RBC count.
Normal RBC count.
  • Because they lack a nucleus, RBCs stay viable for only about 120 days and must be replaced at the same rate as they disappear from the blood (= 2.5 million cell/second).
  1. image descriptionA high number of RBCs per volume of blood is referred to as polycythemia. When this abnormality occurs, it can increase blood volume, pressure, and viscosity.
Magnified view of a drop of blood containing WBCs, platelets, and a normal RBC count.
Magnified view of a drop of blood containing WBCs, platelets, and a high RBC count.
High RBC count.
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  1. image descriptionA low number of RBCs of blood reduces the hemoglobin concentration, which is measured in grams Hb per deciliter (100 milliliters) of whole blood:
  • 14 – 18 grams/dL in males
  • 12 – 16 grams/dL in females
Magnified view of a drop of blood containing WBCs, platelets, and a normal RBC count.
Magnified view of a drop of blood containing WBCs, platelets, and a low RBC count.
Low RBC count.
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  • A low hemoglobin concentration, which is called anemia, decreases oxygen (O2) delivery to the tissues.