A blood cell, also called a hematocyte, is a cell produced by hematopoiesis and is normally found in blood. In mammals, these fall into three general categories:

Red blood cells – Erythrocytes

White blood cells – Leukocytes

Platelets – Thrombocytes.

Together, these three kinds of blood cells add up to a total 45% of the blood tissue by volume, with the remaining 55% of the volume composed of plasma, the liquid component of blood.

This volume percentage hematocrit is measured by centrifuge or flow cytometry and is 45% of cells to total volume in males and 40% in females.

Haemoglobin (the main component of red blood cells) is an iron-containing protein that facilitates transportation of oxygen from the lungs to tissues and carbon dioxide from tissues to the lungs.