Over the centuries blood has been regarded as the essence of life itself. From the beginning of time until the early 20th century blood loss was a common cause of death. Blood is made of straw-colored fluid called Plasma in which are suspended many tiny living cells. These are mostly Red Blood Cells, with some White Cells and smaller cells called Platelets. Altogether the cellular components make up 45% of the blood volume. The rest is fluid.

Percentage of blood is in the body? Approximately 8% of the body weight are blood. Thus a person weighing 50 Kg would have about 4000-ml blood. The average adult has about 5000 ml of blood. Blood volume changes slightly in the same person from time to time, varying with hot weather, muscular exercise, high altitudes and pregnancy.