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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.

Learn how to identify different cells under the microscope with these interactive histology quizzes and labelling exercises.

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.