How Much Is One Unit of Blood?

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A unit of blood is equivalent to approximately 1 pint or 450 milliliters, according to the Canadian Blood Services website. The average patient requires around 4.6 units of blood.

The Canadian Blood Services website states that the average person has five liters of blood in his body. Blood donation is of vital importance to medical treatment of thousands of people every year. Blood products or components are used in treating victims of accidents and during surgery. They are also used for cancer treatments and burn therapy. According to BloodConnect, repeated blood transfusions are the only method of treatment available for patients with blood diseases. Examples of such include severe anaemia, blood cancer and thalassemia.

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.