What is a unit of blood?
Blood is collected in plastic bags which contain a watery fluid which prevents blood from getting coagulated. On an average we draw about 450 ml. of blood from a person, depending on the weight of the donor. This blood, plus the amount of anti coagulant present in the bottle or bag, is known as one unit of blood.
A unit of blood is a little less than a pint (approximately 450 milliliters). The average adult has between 8 and 12 pints of blood and can easily spare one. Blood is composed of cells suspended in liquid. The cells—red cells, white cells and platelets—account for 45% of the volume of blood. The remaining liquid portion is plasma, which is used for direct transfusion or as the starting material for preparation of derivatives such as albumin and clotting factors. Blood can be broken down into its components, so that each unit can be used to treat several different patients.
