As blood volume, the total blood volume of an organism is called.
It is the sum of the liquid ( total plasma volume ) and cellular ( total blood cell volume ) blood components. In adult humans are about 4-6 liters (about 1/ 13 of the body weight, 60 to 98 ml / kg body weight and 2.8 in men and 2.4 liters / m² body surface area in women. )
A sufficient and constant volume of blood is essential for the maintenance of blood pressure, and thus the supply of the body tissues with oxygen and nutrients.
A volume contraction, ie, the decrease in blood volume may be due to the general lack of water in the body, see dehydration ( medicine) or by a mismatch between blood and tissue water due to low protein content, see edema.