How much is a unit of blood?

A unit of blood is 450 milliliters, which is approximately 0.95 pint. An adult has eight to 10 units of blood in his body, while a baby has only about one-half of a unit of blood at birth.

A donor gives one unit of blood and is eligible to do so every 56 days. This amount does not harm the donor, as a healthy body quickly replenishes that amount. It does have the potential, however, to save up to three lives and is invaluable to those in need of it. Medical personnel separate a unit of blood into three parts: plasma, red blood cells and platelets. Different medical conditions require transfusions of one or more of these parts.