Page 8, Architecture of the Circulation, Dr. D. Penney

Location of Blood Volume:

With respect to the body fluid compartments, water makes up about 60% of the body weight. This is determined by dye-dilution using heavy water (D2O) or aminopyrine. The intracellular fluid volume holds 2/3's of the body water, or 40% of body weight, whereas the extracellular fluid volume holds 1/3 of the body water, or 20% of body weight. Extracellular water can be determined with inulin, a substance derived from the artichoke. Interstitial fluid, that fluid between the cells but outside the circulation, makes up 75% of the extracellular fluid volume, blood makes up 25%. Of the blood, plasma constitutes 1/3-1/2 by volume, or about 5% of body weight.

Plasma volume is commonly measured by dye-dilution using Evan's blue or cardiogreen. The formed elements, erythrocytes, leukocytes, and platelets, constitute the other large fractional volume of the blood. Erythrocyte volume is measured by injecting 51Cr tagged erythrocytes.