What Happens to Blood Once You Donate It?

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The entire process of donating blood to transfusion is tracked to ensure safety. HowStuffWorks

Every two seconds in the United States, someone, somewhere needs blood. And let's face it, many of us don't consider giving blood until there's a major disaster where donations are needed. But just one donation has the potential to save up to three lives.

On average, when you donate blood, you provide about 1 pint (473 milliliters) of whole blood — that's about a quarter larger than a Starbucks venti coffee. But in the U.S. alone, there is a need for almost 36,000 units every day. So even if you dread the needle, that quick prick is a small sacrifice.

But have you ever wondered what actually happens after your blood is drawn? Where does it go and how is the process tracked for safety and security? We'll break it down:

Step 1. Donating and Collecting

When you have blood drawn, it's collected in a special bag (and likely a few test tubes) developed with an anticoagulant to prevent the blood from clotting. Each bag and test tube is assigned the same unique ID number to ensure an exact match to the collected blood. Then the blood is placed on ice before it's sent to the lab for testing.

Next, the bags and test tubes of blood are packaged in specialty boxes ready for the laboratory (manufacturing) process. According to Kay Crull, senior vice president, Biomedical Operations, American Red Cross, these boxes are validated to keep the blood products at the right temperature.

Meanwhile, the test tube samples are sent off to the lab for testing to be sure the blood is safe, and to determine the blood type. (The FDA regulates blood testing, collection and blood components through its Center for Biologics Evaluation and Research (CBER).) While that blood is being tested, the blood processing center verifies receipt of the whole blood (about 40 percent of blood donations in the U.S. are processed by the American Red Cross) . Crull calls this part of the process "cradle-to-grave tracking," because from the moment a person donates until the blood's final release, it's tracked.

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Once your blood is drawn and tested, it's separated into plasma, platelets and red blood cells and then stored.

Step 2. Processing and Separation

Next the units of whole blood are separated into specific components. This separation process, which is called component therapy, happens when the blood is spun in a centrifuge. The heavy red cells fall to the bottom, and the blood is divided into transfusable components: red cells, platelets and plasma. The plasma might even be processed further. For instance, plasma can be separated into cryoprecipitate (or cryo), which helps control the risk of bleeding by helping blood to clot.

The red blood cells, plasma and platelets are then heat-sealed to ensure they remain sterile, and the components are refrigerated until they're deemed usable via the lab. Red cells, which also contain an anticoagulant solution to prevent clotting, can be refrigerated at 42 degrees Fahrenheit (6 degrees Celsius) for up to 42 days. Plasma (and cryo), on the other hand, are frozen at minus 27 degrees F. Because the proteins in plasma are more stable than those in red blood cells, the plasma can be stored up to a year. Platelets must be used within five days, and are stored at room temp in agitators that "rock" them back and forth until they're transfused into a patient.

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Once the blood processing center gets an OK on the blood tests from the lab, the components are ready for use, labeled and delivered to hospitals.

Step 3. Testing and Transfusion

While the components are being stored, the processing center is also still tracking the donation, including manufacturing data, what centrifuge was used to separate the blood, even what time that work was performed. Once the blood processing center gets an OK on the blood tests from the lab, the components are ready for use and labeled. The labels include blood type and expiration dates, and are then affixed to the bags. If the blood is deemed unsafe during the testing, it's tagged with a discard label to maintain the tracking cycle.

When a hospital or treatment centers places an order for blood or plasma, the newly stored components are shipped off in temperature-safe boxes. The blood (and other components) are double-checked for safety and finally they're ready to be transfused into the patient who needs them.

This entire process can take up to three days. That might not seem like a long time, until there's a major disaster or blood shortage. "Looking at a whole blood perspective, there has to be a focus on preparation, not only utilizing the blood that's on the shelf," Crull says.

The American Red Cross says blood supply usually can't keep up with demand because only about 3 percent of people eligible to donate actually do. That's why giving blood is so critical — especially if you're a "universal donor," with O negative blood type. It can be transfused into any patient with any blood type. So even if you're terrified of giving blood, consider it. It could save a life — or three.

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The final step in the process is a last check for blood type and then transfusion into the patient.