To describe the amount of blood in the Engpsh language, you can use phrases such as "blood volume," "blood concentration," or "blood content." For example:
The blood volume of an adult human is about 5 pters.
The blood concentration of oxygen in a healthy person is about 95-100%.
The blood content of red blood cells is typically around 45% for men and 40% for women.
Note that these phrases can be used to describe the amount of blood in the body as a whole, or the amount of a specific component (such as oxygen or red blood cells) in the blood.