When you visit an American Red Cross site to donate, you’re potentially saving at least three lives—but first, your blood must make a few surprising stops.

It goes on ice

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The initial needle-poke part of donating blood is easy and typically takes less than 15 minutes. But before your blood can be used by someone else, it takes some surprising twists and turns, starting with getting iced: The blood donation center staff places your collection bag in a cooler with the others until the donations can be taken for testing and processing; note that the staff will also set aside a tube of your blood for additional testing. They do this with every donor.

At the Red Cross

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Upon arrival at the Red Cross blood processing facility, the collection bags are unpacked and sorted based on the time the blood was donated. “The bags are separated by times, based on the type of product that will be manufactured (or separated into),” says Pampee Young, MD, PhD, Chief Medical Officer of the American Red Cross Biomedical Division. The samples are sent for testing in a laboratory—the technicians are looking for viruses, bacteria, and other potential infections. Find out why everyone should know their blood type.

Blood is separated into three components

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“Most whole blood donations are separated into transfusable components: red cells, platelets, and plasma,” says Dr. Young. Technicians use centrifuges to spin the blood at high speeds and separate the three components. “The testing and processing steps take approximately three days to complete,” says Dr. Young. Each of the three blood components can then be used to save up to three different people.