Blood plasma is obtained by centrifuging an unclotted blood sample. The plasma no longer contains blood cells (platelets, erythrocytes and leukocytes). Unlike blood serum, however, it still contains all coagulation factors that serve as the starting material for plasma fractionation (extraction of proteins from blood plasma).

Plasma is a transport medium for lipids, glucose, hormones, carbon dioxide, metabolites and oxygen as well as coagulation factors. However, its ability to transport oxygen is much lower than that of hemoglobin (red blood cells). The protein content of the blood plasma is necessary in order to maintain the colloid osmotic pressure of the blood.