Each year, about 4 million people need blood transfusions or component therapy-transfusions of one or more of the blood's components. People receiving transfusions may be suffering from traumatic injuries, anemia due to massive bleeding, diseases such as cancer, or blood conditions such as infants born with Rh disease.

"We usually have an adequate blood supply, however, there are times when there are blood shortages," says Ira Shulman, M.D., professor of pathology and director of transfusion medicine for USC. Healthy people 17 and older can donate blood every eight weeks.

Donors are carefully screened through a mini-physical, a lifestyle and medical questionnaire and a simple test to rule out anemia (low levels of iron in the blood). After donation, the blood is rigorously tested for a variety of conditions, including HIV and hepatitis. Shulman says that most people choose not to give blood because they think it takes too long, however, donation usually takes less than one hour.

Also, there is a small, but not insignificant number of Americans who do not give blood for fear of getting a disease, "which is virtually impossible," says Shulman. "Under federal law, needles and equipment used in the blood donation process can't be reused, even on the same patient. Everything is brand new."

Most donors do not experience side effects, although some may experience temporary light-headedness, dizziness, slight bruising of the arm and a decrease in stamina the day after donating. It takes only a few days to replenish the fluid lost from donating blood and a couple of weeks to replace the donated red blood cells.

Shulman recommends scheduling an appointment to donate blood, then getting a good night's sleep and eating a good breakfast before the donation. Most important, "feel good about saving another person's life."